PRACTICE EXAM 1
The real exam has 60 questions and you are given three hours. It’s the same with this exam.
1. Given:
2. public class Bang extends Thread {
3. static Thread t1, t2, t3;
4. public static void main(String[] args) throws Exception {
5. t1 = new Thread(new Bang());
6. t2 = new Thread(new Bang());
7. t3 = new Thread(new Bang());
8. t1.start(); t2.start(); t3.start();
9. }
10. public void run() {
11. for(int i = 0; i < 500; i++) {
12. System.out.print(Thread.currentThread().getId() + " ");
13. if(i == 250)
14. try {
15. System.out.print("**" + t1.getId() + "**");
16. t1.sleep(600);
17. }
18. catch (Exception e) { }
19. } } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. An exception is thrown at runtime.
C. Bang will execute for a second or two.
D. Bang will execute for at least 10 minutes.
E. Thread t1 will almost certainly be the last thread to finish.
F. Thread t1 will almost certainly be the first thread to finish.
G. It’s difficult to predict which thread will be the last to finish.
2. Given:
3. public class Dec26 {
4. public static void main(String[] args) {
5. short a1 = 6;
6. new Dec26().go(a1);
7. new Dec26().go(new Integer(7));
8. }
9. void go(Short x) { System.out.print("S "); }
10. void go(Long x) { System.out.print("L "); }
11. void go(int x) { System.out.print("i "); }
12. void go(Number n) { System.out.print("N "); }
13. }
What is the result?
A. i L
B. i N
C. S L
D. S N
E. Compilation fails.
F. An exception is thrown at runtime.
3. Given:
1. public class Fellowship {
2. public static void main(String[] args) {
3. // insert code here
4. }
5. }
6. class Numinor {
7. enum Members {
8. HOBBITS(48), ELVES(74), DWARVES(50);
9. int height;
10. Members(int h) { height = h; }
11. int getHeight() { return height; }
12. }
13. }
And these four lines of code to be inserted, independently at line 3:
I. int h0 = Numinor.Members.HOBBITS.getHeight();
II. int h1 = Numinor.Members.getHeight();
III. int h2 = Members.HOBBITS.getHeight();
IV. int h3 = Members.height;
Which are true? (Choose all that apply.)
A. Line I will compile.
B. Line II will compile.
C. Line III will compile.
D. Line IV will compile.
E. Class Numinor will NOT compile.
4. Given:
2. public class Volume {
3. Volume v;
4. int size;
5. public static void main(String[] args) {
6. Volume myV = new Volume();
7. final Volume v2;
8. v2 = myV.doStuff(myV);
9. v2.v.size = 7;
10. System.out.print(v2.size);
11. }
12. Volume doStuff(Volume v3) {
13. v3.size = 5;
14. v3.v = new Volume();
15. return v3;
16. } }
What is the result? (Choose all that apply.)
A. 5
B. 7
C. Compilation fails due to an error on line 8.
D. Compilation fails due to an error on line 9.
E. Compilation fails due to an error on line 13.
F. Compilation fails due to an error on line 14.
5. Given:
3. public class BirdHouse {
4. public static void main(String[] args) {
5. String r = "0";
6. int x = -1, y = -5;
7. if(x < 5)
8. if(y > 0)
9. if(x > y)
10. r += "1";
11. else r += "2";
12. else r += "3";
13. else r += "4";
14. System.out.println(r);
15. } }
What is the result?
A. 0
B. 01
C. 02
D. 03
E. 013
F. 023
G. Compilation fails.
6. Given:
1. class c1 { }
2. class c2 { }
3. interface i1 { }
4. interface i2 { }
5. class A extends c2 implements i1 { }
6. class B implements i1 implements i2 { }
7. class C implements c1 { }
8. class D extends c1, implements i2 { }
9. class E extends i1, i2 { }
10. class F implements i1, i2 { }
What is the result? (Choose all that apply.)
A. Class A does not compile.
B. Class B does not compile.
C. Class C does not compile.
D. Class D does not compile.
E. Class E does not compile.
F. Class F does not compile.
G. Compilation succeeds for all of the classes.
7. Given that "it, IT" and "pt" are valid Locale codes, and given:
41. Date d = new Date();
42. DateFormat df;
43. Locale[] la = {new Locale("it", "IT"), new Locale("pt")};
44. for(Locale l: la) {
45. df = DateFormat.getDateInstance(DateFormat.FULL, l);
46. System.out.println(d.format(df));
47. }
Which are true? (Choose all that apply.)
A. An exception will be thrown at runtime.
B. Compilation fails due to an error on line 43.
C. Compilation fails due to an error on line 45.
D. Compilation fails due to an error on line 46.
E. Classes from the java.text package are used in this code.
F. Classes from the java.util package are used in this code.
8. Given:
2. class SuperCool {
3. static String os = "";
4. void doStuff() { os += "super "; }
5. }
6. public class Cool extends SuperCool {
7. public static void main(String[] args) {
8. new Cool().go();
9. }
10. void go() {
11. SuperCool s = new Cool();
12. Cool c = (Cool)s;
13. // insert code here
14. }
15. void doStuff() { os += "cool "; }
16. }
If the rest of the code compiles, which line(s) of code, inserted independently at line 13, compile? (Choose all that apply.)
A. c.doStuff();
B. s.doStuff();
C. this.doStuff();
D. super.doStuff();
E. c.super.doStuff();
F. s.super.doStuff();
G. this.super.doStuff();
H. There are other errors in the code.
9. Given:
5. static String s = "";
6. public static void main(String[] args) {
7. try { doStuff(args); }
8. catch (Error e) { s += "e "; }
9. s += "x ";
10. System.out.println(s);
11. }
12. static void doStuff(String[] args) {
13. if(args.length == 0)
14. throw new IllegalArgumentException();
15. s += "d ";
16. }
And, if the code compiles, and given a java invocation with no arguments, what is the result? (Choose all that apply.)
A. d x
B. e x
C. d e x
D. Compilation fails due to an error on line 8.
E. Compilation fails due to an error on line 12.
F. Compilation fails due to an error on line 14.
G. An uncaught IllegalArgumentException is thrown.
10. Given:
2. class Paratrooper implements Runnable {
3. public void run() {
4. System.out.print(Thread.currentThread().getName() + " ");
5. } }
6. public class Jump {
7. static Paratrooper p;
8. static { p = new Paratrooper(); }
9. { Thread t1 = new Thread(p, "bob"); t1.start(); }
10. public static void main(String[] args) {
11. new Jump();
12. new Thread(new Runnable() { public void run()
{ ; }}, "carol").start();
13. new Thread(new Paratrooper(), "alice").start();
14. }
15. Jump() { Thread t2 = new Thread(p, "ted"); t2.start(); }
16. }
Which are true? (Choose all that apply.)
A. The output could be ted bob alice
B. The output could be bob alice carol
C. The output could be bob carol ted alice
D. Compilation fails due to an error on line 8.
E. Compilation fails due to an error on line 9.
F. Compilation fails due to an error on line 12.
G. Compilation fails due to an error on line 15.
11. Use the fragments below to fill in the blanks so that the code will compile, and when invoked with:
java Dropkick fish
will produce the output: "1 4 "
Note: All of the blanks must be filled, not all the fragments will be used, and fragments can be used only once.
Code:
public class Dropkick {
public static void main(String[] args) {
boolean test = false;
String[] s = {"duck", null, "frog"};
if((s[1] == null) ___ (s[1].length() == 0)) System.out.print("1 ");
if((s[2] == null) ___ (test ___ true)) System.out.print("2 ");
if((s[0].equals("duck")) ___ (args[0].equals("fish")))
System.out.print("3 ");
if((args[0] != null) && (______)) System.out.print("4 ");
}
}
Fragments:
|, ||, &, &&, ^, <, %, =, ==, !=, false, test, s[1]
12. Which are true? (Choose all that apply.)
A. For a specific object, it’s NOT possible for finalize() to be invoked more than once.
B. It’s possible for objects, on whom finalize() has been invoked by the JVM, to avoid the GC.
C. Overriding finalize() ensures that objects of that type will always be GCed when they become eligible.
D. The finalize() method is invoked only for GC-eligible objects that are NOT part of “islands of isolation.”
E. For every object that the GC considers collecting, the GC remembers whether finalize() has been invoked for that specific object.
13. Given that:
Exception is the superclass of IOException and
IOException is the superclass of FileNotFoundException
and
2. import java.io.*;
3. class Author {
4. protected void write() throws IOException { }
5. }
6. public class Salinger extends Author {
7. private void write(int x) { }
8. protected void write(long x) throws FileNotFoundException { }
9. protected void write(boolean x) throws Exception { }
10. protected int write(short x) { return 7; }
11. public void write() { }
12. }
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 7.
C. Compilation fails due to an error on line 8.
D. Compilation fails due to an error on line 9.
E. Compilation fails due to an error on line 10.
F. Compilation fails due to an error on line 11.
14. Given:
2. class Chilis {
3. Chilis(String c, int h) { color = c; hotness = h; }
4. String color;
5. int hotness;
6. public boolean equals(Object o) {
7. if(this == (Chilis)o) return true;
8. return false;
9. }
10. public String toString() { return color + " " + hotness; }
11. }
If instances of class Chilis are to be used as keys in a Map, which are true? (Choose all that apply.)
A. Without overriding hashCode(), the code will not compile.
B. As it stands, the equals() method has been legally overridden.
C. It’s possible for such keys to find the correct entries in the Map.
D. It’s NOT possible for such keys to find the correct entries in the Map.
E. As it stands, the Chilis class legally supports the equals() and hashCode() contracts.
F. If hashCode() was correctly overridden, it would make retrieving Map entries by key easier.
15. Given:
2. public class Contact {
3. private String name;
4. private String city;
5. String getName() { return name; }|
6. void setName(String n) { name = n; }
7. void setCity(String c) {
8. if(c == null) throw new NullPointerException();
9. city = c;
10. }
11. String getCity() { return city; }
12. }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The class is well encapsulated.
C. The setCity() method is an example of loose coupling.
D. The setCity() method has better encapsulation than setName().
E. The setCity() method is cohesive; the setName() method is not.
16. Given the current directory is bigApp, and the directory structure:
bigApp
|-- classes
|-- Cloned.class
And the file:
public class Cloned {
public static void main(String[] args) {
System.out.println("classes");
assert(Integer.parseInt(args[0]) > 0);
} }
Which will produce the output "classes" followed by an AssertionError? (Choose all that apply.)
A. java -cp classes Cloned -4
B. java -cp classes -ea Cloned
C. java -ea-cp classes Cloned -4
D. java -ea -cp classes Cloned 4
E. java -ea, cp classes Cloned 4
F. java -ea -cp classes Cloned -4
G. java -cp classes Cloned -4 -ea
17. Given:
1. interface Syrupable {
2. void getSugary();
3. }
4. abstract class Pancake implements Syrupable { }
5.
6. class BlueBerryPancake implements Pancake {
7. public void getSugary() { ; }
8. }
9. class SourdoughBlueBerryPancake extends BlueBerryPancake {
10. void getSugary(int s) { ; }
11. }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 2.
C. Compilation fails due to an error on line 4.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 9.
G. Compilation fails due to an error on line 10.
18. Given:
1. public class Endless {
2. public static void main(String[] args) {
3. int i = 0;
4. short s = 0;
5. for(int j = 0, k = 0; j < 3; j++) ;
6. for(int j = 0; j < 3; counter(j)) ;
7. for(int j = 0, int k = 0; j < 3; j++) ;
8. for(; i < 5; counter(5), i++) ;
9. for(i = 0; i < 3; i++, System.out.print("howdy ")) ;
10. }
11. static int counter(int y) { return y + 1; }
12. }
What is the result? (Choose all that apply.)
A. howdy howdy howdy
B. The code runs in an endless loop.
C. Compilation fails due to an error on line 5.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 8.
G. Compilation fails due to an error on line 9.
19. Given:
2. class Big {
3. void doStuff(int x) { }
4. }
5. class Heavy extends Big {
6. // void doStuff(byte b) { }
7. // protected void doStuff(int x) throws Exception { }
8. }
9. public class Weighty extends Heavy {
10. // void doStuff(int x) { }
11. // String doStuff(int x) { return "hi"; }
12. // public int doStuff(int x) { return 7; }
13. // private int doStuff(char c) throws Error { return 1; }
14. }
Which method(s), if uncommented independently, compile? (Choose all that apply.)
A. Line 6
B. Line 7
C. Line 10
D. Line 11
E. Line 12
F. Line 13
20. Which are true? (Choose all that apply.)
A. A given TreeSet’s ordering cannot be changed once it’s created.
B. The java.util.Properties class is conceptually more like a List than like a Map.
C. It’s a reasonable design choice to use a LinkedList when you want to design queue-like functionality.
D. Of the main types of collections flavors (Lists, Sets, Maps), Queues are conceptually most like Sets.
E. It’s programmatically easier to perform a non-destructive traversal of a PriorityQueue than a LinkedList.
F. Classes that implement the Set interface are usually well suited for applications that require access to a collection based on an index.
21. Given the following directory structure:
If test, testdir, subdir, and subdir2 are all directories, and Finder.class and testfile.txt are files, and given:
import java.io.*;
public class Finder {
public static void main(String[] args) throws IOException {
String[] files = new String[100];
File dir = new File(args[0]);
files = dir.list();
System.out.println(files.length);
} }
And, if the code compiles, the invocation:
java Finder testdir
What is the result?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 100
G. Compilation fails.
H. An exception is thrown at runtime.
22. Given:
1. public class Grids {
2. public static void main(String[] args) {
3. int [][] ia2;
4. int [] ia1 = {1,2,3};
5. Object o = ia1;
6. ia2 = new int[3][3];
7. ia2[0] = (int[])o;
8. ia2[0][0] = (int[])o;
9. } }
What is the result? (Choose all that apply.)
A. Compilation fails due to an error on line 4.
B. Compilation fails due to an error on line 5.
C. Compilation fails due to an error on line 6.
D. Compilation fails due to an error on line 7.
E. Compilation fails due to an error on line 8.
F. Compilation succeeds and the code runs without exception.
G. Compilation succeeds and an exception is thrown at runtime.
23. Given:
3. public class OffRamp {
4. public static void main(String[] args) {
5. int [] exits = {0,0,0,0,0,0};
6. int x1 = 0;
7.
8. for(int x = 0; x < 4; x++) exits[0] = x;
9. for(int x = 0; x < 4; ++x) exits[1] = x;
10.
11. x1 = 0; while(x1++ < 3) exits[2] = x1;
12. x1 = 0; while(++x1 < 3) exits[3] = x1;
13.
14. x1 = 0; do { exits[4] = x1; } while(x1++ < 7);
15. x1 = 0; do { exits[5] = x1; } while(++x1 < 7);
16.
17. for(int x: exits)
18. System.out.print(x + " ");
19. } }
What is the result?
A. 3 3 2 2 6 6
B. 3 3 3 2 7 6
C. 3 3 3 2 7 7
D. 4 3 3 2 7 6
E. 4 3 3 2 7 7
F. Compilation fails.
24. Given:
2. import java.util.*;
3. public class HR {
4. public static void main(String[] args) {
5. List<Integer> i = new Vector<Integer>();
6. i.add(3); i.add(2); i.add(5);
7. int ref = 1;
8. doStuff(ref);
9. System.out.println(i.get(ref));
10. }
11. static int doStuff(int x) {
12. return ++x;
13. } }
What is the result?
A. 2
B. 3
C. 5
D. Compilation fails.
E. An exception is thrown at runtime.
25. Given:
2. import java.util.*;
3. public class Vinegar {
4. public static void main(String[] args) {
5. Set<Integer> mySet = new HashSet<Integer>();
6. do1(mySet, "0"); do1(mySet, "a");
7. do2(mySet, "0"); do2(mySet, "a");
8. }
9. public static void do1(Set s, String st) {
10. s.add(st);
11. s.add(Integer.parseInt(st));
12. }
13. public static void do2(Set<Integer> s, String st) {
14. s.add(st);
15. s.add(Integer.parseInt(st));
16. } }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 6.
C. Compilation fails due to an error on line 13.
D. Compilation fails due to an error on line 14.
E. Compilation fails due to an error on line 15.
F. If only the line(s) of code that don’t compile are removed, the code will run without exception.
G. If only the line(s) of code that don’t compile are removed, the code will throw an exception.
26. Given:
3. class Employee {
4. private String name;
5. void setName(String n) { name = n; }
6. String getName() { return name; }
7. }
8. interface Mungeable {
9. void doMunging();
10. }
11. public class MyApp implements Mungeable {
12. public void doMunging() { ; }
13. public static void main(String[] args) {
14. Employee e = new Employee();
15. e.setName("bob");
16. System.out.print(e.getName());
17. } }
Which are true? (Choose all that apply.)
A. MyApp is-a Employee.
B. MyApp is-a Mungeable.
C. MyApp has-a Employee.
D. MyApp has-a Mungeable.
E. The code is loosely coupled.
F. The Employee class is well encapsulated.
27. Given that FileNotFoundException extends IOException, and given:
2. import java.io.*;
3. public class MacPro extends Laptop {
4. public static void main(String[] args) {
5. new MacPro().crunch();
6. }
7. // insert code here
8. }
9. class Laptop {
10. void crunch() throws IOException { }
11. }
Which method(s), inserted independently at line 7, compile? (Choose all that apply.)
A. void crunch() { }
B. void crunch() throws Exception { }
C. void crunch(int x) throws Exception { }
D. void crunch() throws RuntimeException { }
E. void crunch() throws FileNotFoundException { }
28. Given:
2. class Horse {
3. String hands = "15";
4. }
5. class GaitedPony extends Horse {
6. static String hands = "14";
7. public static void main(String[] args) {
8. String hands = "13.2";
9. String result = new GaitedPony().getSize(hands);
10. System.out.println(" " + result);
11. }
12. String getSize(String s) {
13. System.out.print("hands: " + s);
14. return hands;
15. } }
What is the result?
A. 14
B. 15
C. hands: 13.2 14
D. hands: 13.2 15
E. Compilation fails.
F. An exception is thrown at runtime.
29. Given:
2. public class Humping {
3. public static void main(String[] args) {
4. String r = "-";
5. char[] c = {′a′, ′b′, ′c′, ′z′};
6. for(char c1: c)
7. switch (c1) {
8. case ′a′: r += "a";
9. case ′b′: r += "b"; break;
10. default: r += "X";
11. case ′z′: r+= "z";
12. }
13. System.out.println(r);
14. } }
What is the result?
A. -abXz
B. -abbXz
C. -abbXzz
D. -abbXzXz
E. Compilation fails due to a single error.
F. Compilation fails due to multiple errors.
30. Given:
1. import java.util.*;
2. public class Garage {
3. public static void main(String[] args) {
4. Map<String, String> hm = new HashMap<String, String>();
5. String[] k = {null, "2", "3", null, "5"};
6. String[] v = {"a", "b", "c", "d", "e"};
7.
8. for(int i=0; i<5; i++) {
9. hm.put(k[i], v[i]);
10. System.out.print(hm.get(k[i]) + " ");
11. }
12. System.out.print(hm.size() + " " + hm.values() + "
");
13. } }
What result is most likely?
A. a b c a e 4 [c, b, a, e]
B. a b c d e 4 [c, b, a, e]
C. a b c d e 4 [c, d, b, e]
D. a b c, followed by an exception.
E. An exception is thrown with no other output.
F. Compilation fails due to error(s) in the code.
31. Given:
2. class Jiggy extends Thread {
3. Jiggy(String n) { super(n); }
4. public void run() {
5. for(int i = 0; i < 100; i++) {
6. if("t1".equals(Thread.currentThread().getName()) && i == 5) {
7. new Jiggy("t3").start();
8. throw new Error();
9. }
10. if("t2".equals(Thread.currentThread().getName()) && i == 5) {
11. new Jiggy("t4").start();
12. throw new Error();
13. }
14. System.out.print(Thread.currentThread().getName() + "-");
15. }
16. }
17. public static void main(String[] args) {
18. Thread t1 = new Jiggy("t1");
19. Thread t2 = new Jiggy("t2");
20. t1.setPriority(1); t2.setPriority(9);
21. t2.start(); t1.start();
22. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. After throwing error(s), t3 will most likely complete before t4.
C. After throwing error(s), t4 will most likely complete before t3.
D. The code will throw one error and then no more output will be produced.
E. The code will throw two errors and then no more output will be produced.
F. After throwing error(s) it’s difficult to determine whether t3 or t4 will complete first.
32. Given:
3. class Stereo { void makeNoise() { assert false; } }
4. public class BoomBox extends Stereo {
5. public static void main(String[] args) {
6. new BoomBox().go(args);
7. }
8. void go(String[] args) {
9. if(args.length > 0) makeNoise();
10. if(!args[0].equals("x")) System.out.println("!x");
11. } }
And, if the code compiles, the invocation:
java -ea BoomBox
What is the result?
A. !x
B. Compilation fails.
C. An AssertionError is thrown.
D. A NullPointerException is thrown.
E. An IllegalArgumentException is thrown.
F. An ArrayIndexOutOfBoundsException is thrown.
33. Given:
1. public class LaSelva extends Beach {
2. LaSelva() { s = "LaSelva"; }
3. public static void main(String[] args) { new LaSelva().go(); }
4. void go() {
5. Beach[] ba = { new Beach(), new LaSelva(), (Beach) new LaSelva() };
6. for(Beach b: ba) System.out.print(b.getBeach().s + " ");
7. }
8. LaSelva getBeach() { return this; }
9. }
10. class Beach {
11. String s;
12. Beach() { s = "Beach"; }
13. Beach getBeach() { return this; }
14. }
What is the result?
A. Beach LaSelva Beach
B. Beach LaSelva LaSelva
C. Beach LaSelva followed by an exception.
D. Compilation fails due to an error at line 5.
E. Compilation fails due to an error at line 6.
F. Compilation fails due to an error at line 8.
G. Compilation fails due to an error at line 13.
34. When using the java.io.Console class, which are true? (Choose all that apply.)
A. Objects of type java.io.Console are created using a constructor from the same class.
B. Objects of type java.io.Console are created using a method from the java.io.File class.
C. Objects of type java.io.Console are created using a method from the java.lang.System class.
D. Objects of type java.io.Console are created using a method from the java.lang.Object class.
E. The method(s) designed to read passwords can optionally disable the echoing of user input.
F. The method(s) designed to read passwords return a char[].
35. Given:
3. public class Stealth {
4. public static void main(String[] args) {
5. Integer i = 420;
6. Integer i2;
7. Integer i3;
8. i2 = i.intValue();
9. i3 = i.valueOf(420);
10. System.out.println((i == i2) + " " + (i == i3));
11. } }
What is the result?
A. true true
B. true false
C. false true
D. false false
E. Compilation fails.
F. An exception is thrown at runtime.
36. Given:
2. import java.io.*;
3. interface Risky {
4. String doStuff() throws Exception;
5. Risky doCrazy();
6. void doInsane();
7. }
8. class Bungee implements Risky {
9. public String doStuff() throws IOException {
10. throw new IOException();
11. }
12. public Bungee doCrazy() { return new Bungee(); }
13. public void doInsane() throws NullPointerException {
14. throw new NullPointerException();
15. } }
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. The Risky interface will not compile.
C. The Bungee.doStuff() method will not compile.
D. The Bungee.doCrazy() method will not compile.
E. The Bungee.doInsane() method will not compile.
37. Given that IllegalArgumentException extends RuntimeException, and given:
11. static String s = "";
12. public static void main(String[] args) {
13. try { doStuff(); }
14. catch (Exception ex) { s += "c1 "; }
15. System.out.println(s);
16. }
17. static void doStuff() throws RuntimeException {
18. try {
19. s += "t1 ";
20. throw new IllegalArgumentException();
21. }
22. catch (IllegalArgumentException ie) { s += "c2 "; }
23. throw new IllegalArgumentException();
24. }
What is the result?
A. c1 t1 c2
B. c2 t1 c1
C. t1 c1 c2
D. t1 c2 c1
E. Compilation fails.
F. An uncaught exception is thrown at runtime.
38. Given:
1. public class Networking {
2. public static void main(String[] args) {
3. List<Integer> i = new LinkedList<Integer>();
4. i.add(4); i.add(2); i.add(5);
5. int r = 1;
6. doStuff(r);
7. System.out.println(i.get(r));
8. }
9. static int doStuff(int x) {
10. return ++x;
11. } }
What is the result?
A. 2
B. 4
C. 5
D. Compilation fails.
E. An exception is thrown at runtime.
39. Given:
1. import java.util.*;
2. public class Unturned {
3. public static void main(String[] args) {
4. String[] towns = {"aspen", "vail", "t-ride", "dillon"};
5. MySort ms = new MySort();
6. Arrays.sort(towns, ms);
7. System.out.println(Arrays.binarySearch(towns, "dillon"));
8. }
9. static class MySort implements Comparator<String> {
10. public int compare(String a, String b) {
11. return b.compareTo(a);
12. } } }
What is the most likely result?
A. -1
B. 1
C. 2
D. 3
E. Compilation fails.
F. An exception is thrown at runtime.
40. Given:
2. class Weed {
3. protected static String s = "";
4. final void grow() { s += "grow "; }
5. static final void growFast() { s += "fast "; }
6. }
7. public class Thistle extends Weed {
8. void grow() { s += "t-grow "; }
9. void growFast() { s+= "t-fast "; }
10. }
Which are the FEWEST change(s) required for this code to compile? (Choose all that apply.)
A. s must be marked public.
B. Thistle.grow() must be marked final.
C. Weed.grow() must NOT be marked final.
D. Weed.growFast() must NOT be marked final.
E. Weed.growFast() must NOT be marked static.
F. Thistle.growFast() must be removed from the class.
41. Given:
2. import java.util.regex.*;
3. public class Decaf {
4. public static void main(String[] args) {
5. Pattern p = Pattern.compile(args[0]);
6. Matcher m = p.matcher(args[1]);
7. while(m.find())
8. System.out.print(m.group() + " ");
9. } }
And the three command-line invocations:
I. java Decaf "0([0-7])?" "1012 0208 430"
II. java Decaf "0([0-7])*" "1012 0208 430"
III. java Decaf "0([0-7])+" "1012 0208 430"
Which are true? (Choose all that apply.)
A. All three invocations will return valid octal numbers.
B. None of the invocations will return valid octal numbers.
C. Only invocations II and III will return valid octal numbers.
D. All three invocations will return the same set of valid octal numbers.
E. Of those invocations that return only valid octal numbers, each invocation will return a different set of valid octal numbers.
42. Given:
1. class Locker extends Thread {
2. private static Thread t;
3. public void run() {
4. if(Thread.currentThread() == t) {
5. System.out.print("1 ");
6. synchronized(t) { doSleep(2000); }
7. System.out.print("2 ");
8. } else {
9. System.out.print("3 ");
10. synchronized(t) { doSleep(1000); }
11. System.out.print("4 ");
12. }
13. }
14. private void doSleep(long delay) {
15. try { Thread.sleep(delay); } catch(InterruptedException ie) { ; }
16. }
17. public static void main(String args[]) {
18. t = new Locker();
19. t.start();
20. new Locker().start();
21. } }
Assuming that sleep() sleeps for about the amount of time specified in its argument, and that all other code runs almost instantly, which are true? (Choose all that apply.)
A. Compilation fails.
B. An exception could be thrown.
C. The code could cause a deadlock.
D. The output could be 1 3 4 2
E. The output could be 1 3 2 4
F. The output could be 3 1 4 2
G. The output could be 3 1 2 4
43. Fill in the blanks using the fragments below, so that the code compiles and produces the output: "1 3 2 3 2 "
Note: You might not need to fill in all of the blanks. Also, you won’t use all of the fragments, and each fragment can be used only once.
Code:
Fragments:
44. Given:
2. public class Later {
3. public static void main(String[] args) {
4. boolean earlyExit = new Later().test1(args);
5. if(earlyExit) assert false;
6. new Later().test2(args);
7. }
8. boolean test1(String[] a) {
9. if (a.length == 0) return false;|
10. return true;
11. }
12. private void test2(String[] a) {
13. if (a.length == 2) assert false;
14. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The assertion on line 5 is appropriate.
C. The assertion on line 13 is appropriate.
D. "java -ea Later" will run without error.
E. "java -ea Later x" will run without error.
F. "java -ea Later x y" will run without error.
G. "java -ea Later x y z" will run without error.
45. Given:
343. String s = "1234";
344. StringBuilder sb =
345. new StringBuilder(s.substring(2).concat("56").replace("7","6"));
346. System.out.println(sb.append("89").insert(3,"x"));
What is the result?
A. 34×5689
B. 345×689
C. 345×789
D. 23×45689
E. 23×45789
F. Compilation fails.
46. Given the following pseudo-code design for a new accounting system:
class Employee
maintainEmployeeInfo()
connectToRDBMS()
class Payroll
setStateTaxCodes()
findEmployeesByState()
class Utilities
getNetworkPrinter()
Assuming the class and method names provide good definitions of their own functionalities, which are probably true? (Choose all that apply.)
A. These classes appear to have low cohesion.
B. These classes appear to have high cohesion.
C. These classes appear to have weak validation.
D. These classes appear to have strong validation.
E. These classes appear to have weak encapsulation.
F. These classes appear to have strong encapsulation.
47. Given:
2. class Dog {
3. void makeNoise() { System.out.print("bark "); }
4. static void play() { System.out.print("catching "); }
5. }
6. class Bloodhound extends Dog {
7. void makeNoise() { System.out.print("howl "); }
8. public static void main(String[] args) {
9. new Bloodhound().go();
10. super.play();
11. super.makeNoise();
12. }
13. void go() {
14. super.play();
15. makeNoise();
16. super.makeNoise();
17. } }
What is the result? (Choose all that apply.)
A. catching howl bark catching bark
B. catching howl howl catching howl
C. catching howl bark, then an exception.
D. Compilation fails due to an error on line 10.
E. Compilation fails due to an error on line 11.
F. Compilation fails due to an error on line 14.
48. Given:
3. public class Baskin {
4. public static void main(String[] args) {
5. int i = 4;
6. int j = 1;
7.
8. assert(i > Integer.valueOf(args[0]));
9. assert(j > Integer.valueOf(args[0])): "error 1";
10. assert(j > i): "error 2": "passed";
11. } }
And, if the code compiles, given the following two command-line invocations:
I. java -ea Baskin 2
II. java -ea Baskin 0
Which are true? (Choose all that apply.)
A. Compilation fails.
B. Invocations I and II will throw an AssertionError that will add String data to the program’s execution log.
C. Invocations I and II will throw an AssertionError that will add String data to the program’s stack trace.
D. Not all of the assert statements use assertions appropriately.
49. Given:
1. import java.util.*;
2. class Priorities {
3. public static void main(String[] args) {
4. PriorityQueue toDo = new PriorityQueue();
5. toDo.add("dishes");
6. toDo.add("laundry");
7. toDo.add("bills");
8. toDo.offer("bills");
9. System.out.print(toDo.size() + " " + toDo.poll());
10. System.out.print(" " + toDo.peek() + " " + toDo.poll());
11. System.out.println(" " + toDo.poll() + " " + toDo.poll());
12. } }
What is the result?
A. 3 bills dishes laundry null null
B. 3 bills bills dishes laundry null
C. 3 dishes dishes laundry bills null
D. 4 bills bills dishes laundry null
E. 4 bills bills bills dishes laundry
F. 4 dishes laundry laundry bills bills
G. Compilation fails.
H. An exception is thrown at runtime.
50. Given that the working directory is bigApp, and the following directory structure:
And the code:
1. public class BigAppClass2 { int doMore() { return 17; } }
And the following command-line invocations:
I. javac -d source/com/wickedlysmart/BigAppClass2.java
II. javac -d classes source/com/wickedlysmart/BigAppClass2.java
III. javac -d classes/com/wickedlysmart source/com/wickedlysmart/BigAppClass2.java
Which are true? (Choose all that apply.)
A. Invocation I will compile the file and place the .class file in the bigApp directory.
B. Invocation II will compile the file and place the .class file in the classes directory.
C. Invocation I will compile the file and place the .class file in the wickedlysmart directory.
D. Invocation II will compile the file and place the .class file in the wickedlysmart directory.
E. Invocation III will compile the file and place the .class file in the wickedlysmart directory.
51. Given:
1. class Contact {
2. String doStuff() { return "howdy "; }
3. }
4. class Supplier extends Contact {
5. String doStuff() { return "send money "; }
6. public static void main(String[] args) {
7. Supplier s1 = new Supplier();
8. Contact c3 = new Contact();
9. Contact c1 = s1;
10. Supplier s2 = (Supplier) c1;
11. Supplier s3 = (Supplier) c3;
12. Supplier s4 = new Contact();
13. } }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. The code runs without exception.
C. If the line(s) of code that do NOT compile (if any) are removed, the code runs without exception.
D. If the line(s) of code that do NOT compile (if any) are removed, the code throws an exception at runtime.
52. Given that Integer.parseInt() throws NumberFormatException, and given:
3. public class Ladder {
4. public static void main(String[] args) {
5. try {
6. System.out.println(doStuff(args));
7. }
8. catch (Exception e) { System.out.println("exc"); }
9. doStuff(args);
10. }
11. static int doStuff(String[] args) {
12. return Integer.parseInt(args[0]);
13. } }
And, if the code compiles, given the invocation:
java Ladder x
What is the result? (Choose all that apply.)
A. 0
B. exc
C. "exc" followed by an uncaught exception.
D. Compilation fails due to an error on line 4.
E. Compilation fails due to an error on line 9.
F. Compilation fails due to an error on line 11.
G. An uncaught exception is thrown with no other output.
53. Given the proper imports and given:
81. String in = "1234,77777,689";
82. Scanner sc = new Scanner(in);
83. sc.useDelimiter(",");
84. while(sc.hasNext())
85. System.out.print(sc.nextInt() + " ");
86. while(sc.hasNext())
87. System.out.print(sc.nextShort() + " ");
What is the result?
A. 1234 77777 689
B. Compilation fails.
C. 1234 77777 689 1234 77777 689
D. 1234 followed by an exception.
E. 1234 77777 689 followed by an exception.
F. 1234 77777 689 1234 followed by an exception.
54. Given:
1. public class Glank implements Vonk { Jooker[] j; }
2. abstract class Bostron { String yoodle; Bostron b; }
3. interface Protefor { }
4. interface Vonk extends Protefor { int x = 7; }
5. class Jooker { Bostron b; }
Which are true? (Choose all that apply.)
A. Glanks have a Bostron.
B. Jookers implement Protefors.
C. Glanks implement Bostrons.
D. Jookers have a String.
E. Bostrons implement Vonks.
F. Bostrons have a Bostron.
55. Given that the root directory contains a subdirectory called "office" that contains some files for a Java application, if "X" and "Y" are unknown arguments, and the following command is invoked from the root directory in order to create a JAR file containing the office directory:
jar -cf X Y
Which are true? (Choose all that apply.)
A. X should be the file name of the JAR file, and Y should be "office".
B. X should be "office", and Y should be the file name of the JAR file.
C. Specifying a file name of the JAR file here is optional.
D. If a file name is not specified here, a file named office.jar will be created.
E. The file name, if specified, must be ended with .jar extension.
F. It is required that the "office" directory must initially have a subdirectory called "META-INF".
G. All of the files other than .java and .class files must be initially placed in the META-INF directory.
56. Given a partial API:
Final class Items implements no interfaces and has one constructor:
Items(String name, int value)
And given that you want to make collections of Items objects and sort them (using classes and interfaces in java.lang or java.util), sometimes by name, and sometimes by value, which are true? (Choose all that apply.)
A. It’s likely that you’ll use the Arrays class.
B. It’s likely that you’ll use the Collections class.
C. It’s likely that you’ll implement Comparable at least twice.
D. It’s likely that you’ll implement Comparator at least twice.
E. It’s likely that you’ll implement the compare() method at least twice.
F. It’s likely that you’ll implement the compareTo() method at least twice.
57. Given:
1. import java.util.*;
2. public class Drunken {
3. public static void main(String[] args) {
4. Set<Stuff> s = new HashSet<Stuff>();
5. s.add(new Stuff(3)); s.add(new Stuff(4)); s.add(new Stuff(4));
6. s.add(new Stuff(5)); s.add(new Stuff(6));
7. s = null;
8. // do more stuff
9. }
10. }
11. class Stuff {
12. int value;
13. Stuff(int v) { value = v; }
14. }
When line 8 is reached, how many objects are eligible for garbage collection?
A. 4
B. 5
C. 6
D. 8
E. 10
F. 12
58. Given:
1. public class Hose <E extends Hose> {
2. E innerE;
3. public static E doStuff(E e, Hose<E> e2) {
4. // insert code here
5. }
6. public E getE() {
7. return innerE;
8. } }
Which can be inserted, independently at line 4, for the code to compile? (Choose all that apply.)
A. return e;
B. return e.getE();
C. return e2;
D. return e2.getE();
E. return new Hose().getE();
F. Compilation fails regardless of which return is inserted.
59. Given the following method signatures from ArrayList:
boolean add(E e)
protected void removeRange(int fromIndexInclusive, int toIndexExclusive)
int size()
and given:
2. import java.util.*;
3. public class MyUtil extends ArrayList {
4. public static void main(String[] args) {
5. MyUtil m = new MyUtil();
6. m.add("w"); m.add("x"); m.add("y"); m.add("z");
7. m.removeRange(1,3);
8. System.out.print(m.size() + " ");
9. MyUtil m2 = new MyUtil2().go();
10. System.out.println(m2.size());
11. }
12. }
13. class MyUtil2 {
14. MyUtil go() {
15. MyUtil m2 = new MyUtil();
16. m2.add("1"); m2.add("2"); m2.add("3");
17. m2.removeRange(1,2);
18. return m2;
19. } }
What is the result?
A. 1 1
B. 1 2
C. 2 1
D. 2 2
E. An exception is thrown at runtime.
F. Compilation fails due to a single error.
G. Compilation fails due to multiple errors.
60. Given:
2. public class Hug implements Runnable {
3. static Thread t1;
4. static Hold h, h2;
5. public void run() {
6. if(Thread.currentThread().getId() == t1.getId()) h.adjust();
7. else h2.view();
8. }
9. public static void main(String[] args) {
10. h = new Hold();
11. h2 = new Hold();
12. t1 = new Thread(new Hug());
13. t1.start();
14. new Thread(new Hug()).start();
15. } }
16. class Hold {
17. static int x = 5;
18. synchronized void adjust() {
19. System.out.print(x-- + " ");
20. try { Thread.sleep(200); } catch (Exception e) { ; }
21. view();
22. }
23. synchronized void view() {
24. try { Thread.sleep(200); } catch (Exception e) { ; }
25. if(x > 0) adjust();
26. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The program could deadlock.
C. The output could be 5 4 3 2 1
D. The program could produce thousands of characters of output.
E. If the sleep() invocations were removed the chances of deadlock would decrease.
F. If the view() method was not synchronized the chances of deadlock would decrease.
Quick answer key
1. C, G
2. B
3. A
4. A
5. D
6. B, C, D, E
7. D, E, F
8. A, B, C, D
9. G
10. A
11. Drag and Drop
12. B and E
13. A
14. B, C, E
15. B
16. F
17. D
18. E
19. A, C, F
20. A, C
21. C
22. E
23. B
24. A
25. D, G
26. B, E, F
27. A, D
28. C
29. C
30. C
31. C
32. F
33. B
34. C, F
35. D
36. A
37. D
38. D
39. A
40. C, F
41. A, E
42. D, E, F, G
43. Drag and Drop
44. D
45. B
46. A, E
47. D, E
48. A, D
49. E
50. B, E
51. D
52. C
53. A
54. A, D, F
55. A
56. B, D, E
57. C
58. F
59. F
60. C
PRACTICE EXAM 1: ANSWERS
1. Given:
2. public class Bang extends Thread {
3. static Thread t1, t2, t3;
4. public static void main(String[] args) throws Exception {
5. t1 = new Thread(new Bang());
6. t2 = new Thread(new Bang());
7. t3 = new Thread(new Bang());
8. t1.start(); t2.start(); t3.start();
9. }
10. public void run() {
11. for(int i = 0; i < 500; i++) {
12. System.out.print(Thread.currentThread().getId() + " ");
13. if(i == 250)
14. try {
15. System.out.print("**" + t1.getId() + "**");
16. t1.sleep(600);
17. }
18. catch (Exception e) { }
19. } } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. An exception is thrown at runtime.
C. Bang will execute for a second or two.
D. Bang will execute for at least 10 minutes.
E. Thread t1 will almost certainly be the last thread to finish.
F. Thread t1 will almost certainly be the first thread to finish.
G. It’s difficult to predict which thread will be the last to finish.
Answer (for Objective 4.2):
C and G are correct. The sleep() method’s argument is in milliseconds. E is incorrect because sleep will be called once on each of the three threads, not on Thread t1 three times. Remember, the sleep() method is static and operates on whichever thread is the currently running thread.
A, B, D, E, and F are incorrect based on the above.
2. Given:
3. public class Dec26 {
4. public static void main(String[] args) {
5. short a1 = 6;
6. new Dec26().go(a1);
7. new Dec26().go(new Integer(7));
8. }
9. void go(Short x) { System.out.print("S "); }
10. void go(Long x) { System.out.print("L "); }
11. void go(int x) { System.out.print("i "); }
12. void go(Number n) { System.out.print("N "); }
13. }
What is the result?
A. i L
B. i N
C. S L
D. S N
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 3.1):
B is correct. First, code written before Java 5 shouldn’t be affected by new Java features like autoboxing, therefore widening is preferred to boxing, producing "i". Second, you can’t widen from one wrapper to another. In this case, Integer is-Not-a Long, but Integer is-a Number.
A, C, D, E, and F are incorrect based on the above.
3. Given:
1. public class Fellowship {
2. public static void main(String[] args) {
3. // insert code here
4. }
5. }
6. class Numinor {
7. enum Members {
8. HOBBITS(48), ELVES(74), DWARVES(50);
9. int height;
10. Members(int h) { height = h; }|
11. int getHeight() { return height; }
12. }
13. }
And these four lines of code to be inserted, independently at line 3:
I. int h0 = Numinor.Members.HOBBITS.getHeight();
II. int h1 = Numinor.Members.getHeight();
III. int h2 = Members.HOBBITS.getHeight();
IV. int h3 = Members.height;
Which are true? (Choose all that apply.)
A. Line I will compile.
B. Line II will compile.
C. Line III will compile.
D. Line IV will compile.
E. Class Numinor will NOT compile.
Answer (for Objective 1.1):
A is the correct syntax to access the height variable.
B, C, and D are incorrect syntax, and E is incorrect because enums can have variables, constructors, and methods.
4. Given:
2. public class Volume {
3. Volume v;
4. int size;
5. public static void main(String[] args) {
6. Volume myV = new Volume();
7. final Volume v2;
8. v2 = myV.doStuff(myV);
9. v2.v.size = 7;
10. System.out.print(v2.size);
11. }
12. Volume doStuff(Volume v3) {
13. v3.size = 5;
14. v3.v = new Volume();
15. return v3;
16. } }
What is the result? (Choose all that apply.)
A. 5
B. 7
C. Compilation fails due to an error on line 8.
D. Compilation fails due to an error on line 9.
E. Compilation fails due to an error on line 13.
F. Compilation fails due to an error on line 14.
Answer (for Objective 7.3):
A is correct. A reference variable marked "final" cannot reference a different object, but the object it references can be changed.
B, C, D, E, and F are incorrect based on the above.
5. Given:
3. public class BirdHouse {
4. public static void main(String[] args) {
5. String r = "0";
6. int x = -1, y = -5;
7. if(x < 5)
8. if(y > 0)
9. if(x > y)
10. r += "1";
11. else r += "2";
12. else r += "3";
13. else r += "4";
14. System.out.println(r);
15. } }
What is the result?
A. 0
B. 01
C. 02
D. 03
E. 013
F. 023
G. Compilation fails.
Answer (for Objective 2.1):
D is correct. Obviously, this is horrible code—we’re trying to toughen you up for the real thing! Work these nested if statements from the inside out. The innermost "if" block is lines 9–11. The next set is lines 8 and 12, and finally lines 7 and 13. Given that, the first "if" is true, so the second "if" is evaluated. Since the second "if" test is false, its associated "else" (line 12) is executed.
A, B, C, E, F, and G are incorrect based on the above.
6. Given:
1. class c1 { }
2. class c2 { }
3. interface i1 { }
4. interface i2 { }
5. class A extends c2 implements i1 { }
6. class B implements i1 implements i2 { }
7. class C implements c1 { }
8. class D extends c1, implements i2 { }
9. class E extends i1, i2 { }
10. class F implements i1, i2 { }
What is the result? (Choose all that apply.)
A. Class A does not compile.
B. Class B does not compile.
C. Class C does not compile.
D. Class D does not compile.
E. Class E does not compile.
F. Class F does not compile.
G. Compilation succeeds for all of the classes.
Answer (for Objective 1.2):
B, C, D, and E are correct, as those classes will NOT compile. For class B, it’s okay to implement two interfaces, but the syntax is incorrect. For class C, classes extend other classes, they don’t implement them. For class D, it’s okay to extend AND implement, but the syntax is wrong. For class E, it’s legal to implement more than one interface, but interfaces are implemented, not extended.
A and F are declared correctly, and option G is incorrect based on the above.
7. Given that "it, IT" and "pt" are valid Locale codes, and given:
41. Date d = new Date();
42. DateFormat df;
43. Locale[] la = {new Locale("it", "IT"), new Locale("pt")};
44. for(Locale l: la) {
45. df = DateFormat.getDateInstance(DateFormat.FULL, l);
46. System.out.println(d.format(df));
47. }
Which are true? (Choose all that apply.)
A. An exception will be thrown at runtime.
B. Compilation fails due to an error on line 43.
C. Compilation fails due to an error on line 45.
D. Compilation fails due to an error on line 46.
E. Classes from the java.text package are used in this code.
F. Classes from the java.util package are used in this code.
Answer (for Objective 3.3):
D, E, and F are correct. It’s okay to mix the two types of Locale on line 43. On line 46, we should use the DateFormat instance to invoke the format() method on the Date instance. The rest of the code is legal.
A, B, and C are incorrect based on the above.
8. Given:
2. class SuperCool {
3. static String os = "";
4. void doStuff() { os += "super "; }
5. }
6. public class Cool extends SuperCool {
7. public static void main(String[] args) {
8. new Cool().go();
9. }
10. void go() {
11. SuperCool s = new Cool();
12. Cool c = (Cool)s;
13. // insert code here
14. }
15. void doStuff() { os += "cool "; }
16. }
If the rest of the code compiles, which line(s) of code, inserted independently at line 13, compile? (Choose all that apply.)
A. c.doStuff();
B. s.doStuff();
C. this.doStuff();
D. super.doStuff();
E. c.super.doStuff();
F. s.super.doStuff();
G. this.super.doStuff();
H. There are other errors in the code.
Answer (for Objective 5.2):
A, B, C, and D are correct. A, B, and C will invoke Cool’s version of doStuff(), and D will invoke SuperCool’s version of doStuff().
E, F, and G are all illegal syntax to try to invoke SuperCool’s version of doStuff(). H is incorrect because the rest of the code is legal.
9. Given:
5. static String s = "";
6. public static void main(String[] args) {
7. try { doStuff(args); }
8. catch (Error e) { s += "e "; }
9. s += "x ";
10. System.out.println(s);
11. }
12. static void doStuff(String[] args) {
13. if(args.length == 0)
14. throw new IllegalArgumentException();
15. s += "d ";
16. }
And, if the code compiles, and given a java invocation with no arguments, what is the result? (Choose all that apply.)
A. d x
B. e x
C. d e x
D. Compilation fails due to an error on line 8.
E. Compilation fails due to an error on line 12.
F. Compilation fails due to an error on line 14.
G. An uncaught IllegalArgumentException is thrown.
Answer (for Objective 2.5):
G is correct. It’s legal, although uncommon to catch Errors. It’s legal to shadow the variable name "args". It’s legal to throw a runtime exception without handling it or declaring it. And finally, the catch block doesn’t catch the exception because exceptions don’t extend from Error.
A, B, C, D, E, and F are incorrect based on the above.
10. Given:
2. class Paratrooper implements Runnable {
3. public void run() {
4. System.out.print(Thread.currentThread().getName() + " ");
5. } }
6. public class Jump {
7. static Paratrooper p;
8. static { p = new Paratrooper(); }
9. { Thread t1 = new Thread(p, "bob"); t1.start(); }
10. public static void main(String[] args) {
11. new Jump();
12. new Thread(new Runnable() { public void run()
{ ; }}, "carol").start();
13. new Thread(new Paratrooper(), "alice").start();
14. }
15. Jump() { Thread t2 = new Thread(p, "ted"); t2.start(); }
16. }
Which are true? (Choose all that apply.)
A. The output could be ted bob alice
B. The output could be bob alice carol
C. The output could be bob carol ted alice
D. Compilation fails due to an error on line 8.
E. Compilation fails due to an error on line 9.
F. Compilation fails due to an error on line 12.
G. Compilation fails due to an error on line 15.
Answer (for Objective 4.1):
A is correct. As shown in this code, threads can be started in init blocks, constructors, and inner classes. The thread started in the inner class uses a run() method that doesn’t print the thread’s name, so "carol" is not in the output.
B, C, D, E, F, and G are incorrect based on the above.
11. Use the fragments below to fill in the blanks so that the code will compile, and when invoked with:
java Dropkick fish
will produce the output: "1 4 "
Note: All of the blanks must be filled, not all the fragments will be used, and fragments can be used only once.
Code:
public class Dropkick {
public static void main(String[] args) {
boolean test = false;
String[] s = {"duck", null, "frog"};
if((s[1] == null) ___ (s[1].length() == 0)) System.out.print("1 ");
if((s[2] == null) ___ (test ___ true)) System.out.print("2 ");
if((s[0].equals("duck")) ___ (args[0].equals("fish")))
System.out.print("3 ");
if((args[0] != null) && (______)) System.out.print("4 ");
}
}
Fragments:
|, ||, &, &&, ^, <, %, =, ==, !=, false, test, s[1]
12. Which are true? (Choose all that apply.)
A. For a specific object, it’s NOT possible for finalize() to be invoked more than once.
B. It’s possible for objects, on whom finalize() has been invoked by the JVM, to avoid the GC.
C. Overriding finalize() ensures that objects of that type will always be GCed when they become eligible.
D. The finalize() method is invoked only for GC-eligible objects that are NOT part of “islands of isolation.”
E. For every object that the GC considers collecting, the GC remembers whether finalize() has been invoked for that specific object.
Answer (for Objective 7.4):
B and E are correct. B is correct because finalize() itself might send a reference to a live thread, thus “uneligible-izing” the object. E is just correct.
A is incorrect because while the JVM will invoke finalize() no more than once per object, your code is free to invoke finalize(). C and D are incorrect because no such rules exist.
13. Given that:
Exception is the superclass of IOException and
IOException is the superclass of FileNotFoundException
and
2. import java.io.*;
3. class Author {
4. protected void write() throws IOException { }
5. }
6. public class Salinger extends Author {
7. private void write(int x) { }
8. protected void write(long x) throws FileNotFoundException { }
9. protected void write(boolean x) throws Exception { }
10. protected int write(short x) { return 7; }
11. public void write() { }
12. }
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 7.
C. Compilation fails due to an error on line 8.
D. Compilation fails due to an error on line 9.
E. Compilation fails due to an error on line 10.
F. Compilation fails due to an error on line 11.
Answer (for Objective 1.4):
A is correct. All of the overrides and overloads are legal.
B, C, D, E, and F are incorrect because it’s legal for overloaded methods to have different return types, throw different exceptions, and have different access modifiers. Overridden methods have stricter requirements, but lines 7–10 are overloaded methods. Line 11 is an overridden method, and it’s legal for overridden methods to have fewer exceptions and less restrictive access modifiers.
14. Given:
2. class Chilis {
3. Chilis(String c, int h) { color = c; hotness = h; }
4. String color;
5. int hotness;
6. public boolean equals(Object o) {
7. if(this == (Chilis)o) return true;
8. return false;
9. }
10. public String toString() { return color + " " + hotness; }
11. }
If instances of class Chilis are to be used as keys in a Map, which are true? (Choose all that apply.)
A. Without overriding hashCode(), the code will not compile.
B. As it stands, the equals() method has been legally overridden.
C. It’s possible for such keys to find the correct entries in the Map.
D. It’s NOT possible for such keys to find the correct entries in the Map.
E. As it stands, the Chilis class legally supports the equals() and hashCode() contracts.
F. If hashCode() was correctly overridden, it would make retrieving Map entries by key easier.
Answer (for Objective 6.2):
B, C, and E are correct. If a class does NOT override equals() and hashCode(), class Object provides a default implementation. The default implementation’s logic is that only two references to THE SAME OBJECT will be considered equal.
Given that, it might appear that equals() has been overridden, but in practice this overridden equals() method performs exactly as the default method performs. Therefore, the equals() and hashCode() methods will support their contracts, although it will be hard for a programmer to use this class for keys in a Map.
A is incorrect because the code compiles. D is incorrect based on the above. F is incorrect because in practice equals() hasn’t really been overridden.
15. Given:
2. public class Contact {
3. private String name;
4. private String city;
5. String getName() { return name; }
6. void setName(String n) { name = n; }
7. void setCity(String c) {
8. if(c == null) throw new NullPointerException();
9. city = c;
10. }
11. String getCity() { return city; }
12. }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The class is well encapsulated.
C. The setCity() method is an example of loose coupling.
D. The setCity() method has better encapsulation than setName().
E. The setCity() method is cohesive; the setName() method is not.
Answer (for Objective 5.1):
B is correct. The setCity() method includes argument validation, which is a good thing. It’s not, by itself, an example of coupling or cohesion. Also, validation doesn’t make a method more encapsulated.
A is incorrect because it’s legal to throw a NullPointerException without handling or declaring it. C, D, and E are incorrect based on the above.
16. Given the current directory is bigApp, and the directory structure:
And the file:
public class Cloned {
public static void main(String[] args) {
System.out.println("classes");
assert(Integer.parseInt(args[0]) > 0);
} }
Which will produce the output "classes" followed by an AssertionError? (Choose all that apply.)
A. java -cp classes Cloned -4
B. java -cp classes -ea Cloned
C. java -ea-cp classes Cloned -4
D. java -ea -cp classes Cloned 4
E. java -ea, cp classes Cloned 4
F. java -ea -cp classes Cloned -4
G. java -cp classes Cloned -4 -ea
Answer (for Objective 7.2):
F is the correct syntax for the java command.
A and G do not enable assertions (in G, the -ea is seen as the second argument). B throws an ArrayIndexOutOfBoundsException. C and E are invalid syntax. D passes the assert test.
17. Given:
1. interface Syrupable {
2. void getSugary();
3. }
4. abstract class Pancake implements Syrupable { }
5.
6. class BlueBerryPancake implements Pancake {
7. public void getSugary() { ; }
8. }
9. class SourdoughBlueBerryPancake extends BlueBerryPancake {
10. void getSugary(int s) { ; }
11. }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 2.
C. Compilation fails due to an error on line 4.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 9.
G. Compilation fails due to an error on line 10.
Answer (for Objective 1.1):
D is correct. Classes extend abstract classes, they don’t implement them.
A, B, C, E, F, and G are incorrect. The method on line 10 doesn’t need to be declared public because it’s an overload of the parent method, not an override.
18. Given:
1. public class Endless {
2. public static void main(String[] args) {
3. int i = 0;
4. short s = 0;
5. for(int j = 0, k = 0; j < 3; j++) ;
6. for(int j = 0; j < 3; counter(j)) ;
7. for(int j = 0, int k = 0; j < 3; j++) ;
8. for(; i < 5; counter(5), i++) ;
9. for(i = 0; i < 3; i++, System.out.print("howdy ")) ;
10. }
11. static int counter(int y) { return y + 1; }
12. }
What is the result? (Choose all that apply.)
A. howdy howdy howdy
B. The code runs in an endless loop.
C. Compilation fails due to an error on line 5.
D. Compilation fails due to an error on line 6.
E. Compilation fails due to an error on line 7.
F. Compilation fails due to an error on line 8.
G. Compilation fails due to an error on line 9.
Answer (for Objective 2.2):
E is correct. When defining multiple variables in a for loop, line 5 uses the correct syntax.
A is incorrect, although if other issues were fixed in the code, line 9 would create that output. B is incorrect, although if line 7 was fixed, line 6 would cause an endless loop because the counter() method is not incrementing the for loop’s "j" variable. C, D, F, and G are incorrect because the rest of the code’s syntax is correct.
19. Given:
2. class Big {
3. void doStuff(int x) { }
4. }
5. class Heavy extends Big {
6. // void doStuff(byte b) { }
7. // protected void doStuff(int x) throws Exception { }
8. }
9. public class Weighty extends Heavy {
10. // void doStuff(int x) { }
11. // String doStuff(int x) { return "hi"; }
12. // public int doStuff(int x) { return 7; }
13. // private int doStuff(char c) throws Error { return 1; }
14. }
Which method(s), if uncommented independently, compile? (Choose all that apply.)
A. Line 6
B. Line 7
C. Line 10
D. Line 11
E. Line 12
F. Line 13
Answer (for Objective 5.4):
A, C, and F are correct. A and F are valid overloads of Big.doStuff(), and C is a valid override of Big.doStuff().
B, D, and E are all illegal overrides of Big.doStuff().
20. Which are true? (Choose all that apply.)
A. A given TreeSet’s ordering cannot be changed once it’s created.
B. The java.util.Properties class is conceptually more like a List than like a Map.
C. It’s a reasonable design choice to use a LinkedList when you want to design queue-like functionality.
D. Of the main types of collections flavors (Lists, Sets, Maps), Queues are conceptually most like Sets.
E. It’s programmatically easier to perform a non-destructive traversal of a PriorityQueue than a LinkedList.
F. Classes that implement the Set interface are usually well suited for applications that require access to a collection based on an index.
Answer (for Objective 6.1):
A and C are correct statements.
B is incorrect because the Properties class is very Map-like. D is incorrect because Queues are most like Lists. E is incorrect because the PriorityQueue class itself provides no non-destructive traversal methods. F is incorrect because Lists are much better than Sets at index-based retrieval.
21. Given the following directory structure:
If test, testdir, subdir, and subdir2 are all directories, and Finder.class and testfile.txt are files, and given:
import java.io.*;
public class Finder {
public static void main(String[] args) throws IOException {
String[] files = new String[100];
File dir = new File(args[0]);
files = dir.list();
System.out.println(files.length);
} }
And, if the code compiles, the invocation:
java Finder testdir
What is the result?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 100
G. Compilation fails.
H. An exception is thrown at runtime.
Answer (for Objective 3.2):
C is correct. File I/O stuff is risky, but it’s okay for main() to throw an exception. The list() method returns a String[] that contains the names of both the files AND subdirectories within the directory specified. Note that the current directory and its contents are not included.
A, B, D, E, F, G, and H are incorrect based on the above.
22. Given:
1. public class Grids {
2. public static void main(String[] args) {
3. int [][] ia2;
4. int [] ia1 = {1,2,3};
5. Object o = ia1;
6. ia2 = new int[3][3];
7. ia2[0] = (int[])o;
8. ia2[0][0] = (int[])o;
9. } }
What is the result? (Choose all that apply.)
A. Compilation fails due to an error on line 4.
B. Compilation fails due to an error on line 5.
C. Compilation fails due to an error on line 6.
D. Compilation fails due to an error on line 7.
E. Compilation fails due to an error on line 8.
F. Compilation succeeds and the code runs without exception.
G. Compilation succeeds and an exception is thrown at runtime.
Answer (for Objective 1.3):
E is correct. Remember that arrays are objects, and that each array dimension is a separate type. So, for instance, ia2 is of type “two dimensional int array”, which is a different type than ia1. Line 8 attempts to assign a one-dimensional array into an int.
A, B, C, and D are incorrect because lines 4–7 perform legal array manipulations. F and G are incorrect based on the above.
23. Given:
3. public class OffRamp {
4. public static void main(String[] args) {
5. int [] exits = {0,0,0,0,0,0};
6. int x1 = 0;
7.
8. for(int x = 0; x < 4; x++) exits[0] = x;
9. for(int x = 0; x < 4; ++x) exits[1] = x;
10.
11. x1 = 0; while(x1++ < 3) exits[2] = x1;
12. x1 = 0; while(++x1 < 3) exits[3] = x1;
13.
14. x1 = 0; do { exits[4] = x1; } while(x1++ < 7);
15. x1 = 0; do { exits[5] = x1; } while(++x1 < 7);
16.
17. for(int x: exits)
18. System.out.print(x + " ");
19. } }
What is the result?
A. 3 3 2 2 6 6
B. 3 3 3 2 7 6
C. 3 3 3 2 7 7
D. 4 3 3 2 7 6
E. 4 3 3 2 7 7
F. Compilation fails.
Answer (for Objective 2.2):
B is correct. With "for" loops, the last things that happen are the iteration expression and then the conditional expression. With "while" loops, the body only executes if the expression is true. With "do" loops, the body executes first, before the expression is evaluated. The final loop is a legal "for each" loop.
A, C, D, E, and F are incorrect based on the above.
24. Given:
2. import java.util.*;
3. public class HR {
4. public static void main(String[] args) {
5. List<Integer> i = new Vector<Integer>();
6. i.add(3); i.add(2); i.add(5);
7. int ref = 1;
8. doStuff(ref);
9. System.out.println(i.get(ref));
10. }
11. static int doStuff(int x) {
12. return ++x;
13. } }
What is the result?
A. 2
B. 3
C. 5
D. Compilation fails.
E. An exception is thrown at runtime.
Answer (for Objective 7.3):
A is correct. The variable "x" is a copy of ref, and when "x" gets incremented, ref does not. Also, the list index is zero-based and instances of Vector aren’t automatically sorted.
B, C, D, and E are incorrect based on the above.
25. Given:
2. import java.util.*;
3. public class Vinegar {
4. public static void main(String[] args) {
5. Set<Integer> mySet = new HashSet<Integer>();
6. do1(mySet, "0"); do1(mySet, "a");
7. do2(mySet, "0"); do2(mySet, "a");
8. }
9. public static void do1(Set s, String st) {
10. s.add(st);
11. s.add(Integer.parseInt(st));
12. }
13. public static void do2(Set<Integer> s, String st) {
14. s.add(st);
15. s.add(Integer.parseInt(st));
16. } }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. Compilation fails due to an error on line 6.
C. Compilation fails due to an error on line 13.
D. Compilation fails due to an error on line 14.
E. Compilation fails due to an error on line 15.
F. If only the line(s) of code that don’t compile are removed, the code will run without exception.
G. If only the line(s) of code that don’t compile are removed, the code will throw an exception.
Answer (for Objective 6.3):
D and G are correct. It’s legal to pass a generic collection to a method that’s expecting a non-generic collection. In do2(), the compiler knows that "s" can contain only Integers and that st is a String. If this line of code is removed, the parseInt() invocation will throw a NumberFormatException when it is passed "a".
A, B, C, E, and F are incorrect based on the above.
26. Given:
3. class Employee {
4. private String name;
5. void setName(String n) { name = n; }
6. String getName() { return name; }
7. }
8. interface Mungeable {
9. void doMunging();
10. }
11. public class MyApp implements Mungeable {
12. public void doMunging() { ; }
13. public static void main(String[] args) {
14. Employee e = new Employee();
15. e.setName("bob");
16. System.out.print(e.getName());
17. } }
Which are true? (Choose all that apply.)
A. MyApp is-a Employee.
B. MyApp is-a Mungeable.
C. MyApp has-a Employee.
D. MyApp has-a Mungeable.
E. The code is loosely coupled.
F. The Employee class is well encapsulated.
Answer (for Objective 5.5):
B, E, and F are correct statements about the code.
A and C are incorrect because the MyApp class “uses” the Employee class, but MyApp isn’t in Employee’s class hierarchy, and MyApp doesn’t “have” an Employee as part of its state. D is similarly incorrect because MyApp doesn’t “have” a Mungeable as part of its state.
27. Given that FileNotFoundException extends IOException, and given:
2. import java.io.*;
3. public class MacPro extends Laptop {
4. public static void main(String[] args) {
5. new MacPro().crunch();
6. }
7. // insert code here
8. }
9. class Laptop {
10. void crunch() throws IOException { }
11. }
Which method(s), inserted independently at line 7, compile? (Choose all that apply.)
A. void crunch() { }
B. void crunch() throws Exception { }
C. void crunch(int x) throws Exception { }
D. void crunch() throws RuntimeException { }
E. void crunch() throws FileNotFoundException { }
Answer (for Objective 2.4):
A and D are correct. It’s legal for an overriding method to throw fewer exceptions, and runtime exceptions are in a class hierarchy separate from checked exceptions.
C would be correct if the invocation on line 5 was either handled or declared because it’s not an override. B is wrong because it’s a broader exception. E would be correct if the invocation on line 5 was either handled or declared.
28. Given:
2. class Horse {
3. String hands = "15";
4. }
5. class GaitedPony extends Horse {
6. static String hands = "14";
7. public static void main(String[] args) {
8. String hands = "13.2";
9. String result = new GaitedPony().getSize(hands);
10. System.out.println(" " + result);
11. }
12. String getSize(String s) {
13. System.out.print("hands: " + s);
14. return hands;
15. } }
What is the result?
A. 14
B. 15
C. hands: 13.2 14
D. hands: 13.2 15
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 1.3):
C is correct. This code shows a kind of variable “shadowing.” In the getSize() method, the question is whether to use the class’s static "hands" variable, or to use the superclass’s instance "hands" variable. The variable in the same class is used.
A, B, D, E, and F are incorrect based on the above.
29. Given:
2. public class Humping {
3. public static void main(String[] args) {
4. String r = "-";
5. char[] c = {′a′, ′b′, ′c′, ′z′};
6. for(char c1: c)
7. switch (c1) {
8. case ′a′: r += "a";
9. case ′b′: r += "b"; break;
10. default: r += "X";
11. case ′z′: r+= "z";
12. }
13. System.out.println(r);
14. } }
What is the result?
A. -abXz
B. -abbXz
C. -abbXzz
D. -abbXzXz
E. Compilation fails due to a single error.
F. Compilation fails due to multiple errors.
Answer (for Objective 2.1):
C is correct. Remember that a matching case represents the entry point for code execution, not the only point that will be executed. Also, even though the default comes before case "z", when the switch variable equals "z" the switch will skip the default and choose case "z".
A, B, D, E, and F are incorrect based on the above.
30. Given:
1. import java.util.*;
2. public class Garage {
3. public static void main(String[] args) {
4. Map<String, String> hm = new HashMap<String, String>();
5. String[] k = {null, "2", "3", null, "5"};
6. String[] v = {"a", "b", "c", "d", "e"};
7.
8. for(int i=0; i<5; i++) {
9. hm.put(k[i], v[i]);
10. System.out.print(hm.get(k[i]) + " ");
11. }
12. System.out.print(hm.size() + " " + hm.values() + "
");
13. } }
What result is most likely?
A. a b c a e 4 [c, b, a, e]
B. a b c d e 4 [c, b, a, e]
C. a b c d e 4 [c, d, b, e]
D. a b c, followed by an exception.
E. An exception is thrown with no other output.
F. Compilation fails due to error(s) in the code.
Answer (for Objective 6.1):
C is correct. It’s legal for a HashMap to have one null key, and if you invoke put() using an existing key, the new value replaces the old value. The values() method does NOT guarantee any ordering.
A, B, D, E, and F are incorrect based on the above.
31. Given:
2. class Jiggy extends Thread {
3. Jiggy(String n) { super(n); }
4. public void run() {
5. for(int i = 0; i < 100; i++) {
6. if("t1".equals(Thread.currentThread().getName()) && i == 5) {
7. new Jiggy("t3").start();
8. throw new Error();
9. }
10. if("t2".equals(Thread.currentThread().getName()) && i == 5) {
11. new Jiggy("t4").start();
12. throw new Error();
13. }
14. System.out.print(Thread.currentThread().getName() + "-");
15. }
16. }
17. public static void main(String[] args) {
18. Thread t1 = new Jiggy("t1");
19. Thread t2 = new Jiggy("t2");
20. t1.setPriority(1); t2.setPriority(9);
21. t2.start(); t1.start();
22. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. After throwing error(s), t3 will most likely complete before t4.
C. After throwing error(s), t4 will most likely complete before t3.
D. The code will throw one error and then no more output will be produced.
E. The code will throw two errors and then no more output will be produced.
F. After throwing error(s) it’s difficult to determine whether t3 or t4 will complete first.
Answer (for Objective 4.2):
C is correct. Threads can be constructed with a name. The errors will stop t1 and t2, but t3 and t4 will continue. The thread t4 will complete before t3 because it more or less “inherits” its priority from the thread that created it, t2.
A, B, D, E, and F are incorrect based on the above.
32. Given:
3. class Stereo { void makeNoise() { assert false; } }
4. public class BoomBox extends Stereo {
5. public static void main(String[] args) {
6. new BoomBox().go(args);
7. }
8. void go(String[] args) {
9. if(args.length > 0) makeNoise();
10. if(!args[0].equals("x")) System.out.println("!x");
11. } }
And, if the code compiles, the invocation:
java -ea BoomBox
What is the result?
A. !x
B. Compilation fails.
C. An AssertionError is thrown.
D. A NullPointerException is thrown.
E. An IllegalArgumentException is thrown.
F. An ArrayIndexOutOfBoundsException is thrown.
Answer (for Objective 2.6):
F is correct. The java invocation passes no arguments to main(), so the args array has a length of 0, makeNoise() is not called, and line 10 throws an exception.
A, B, C, D, and E are incorrect based on the above.
33. Given:
1. public class LaSelva extends Beach {
2. LaSelva() { s = "LaSelva"; }
3. public static void main(String[] args) { new LaSelva().go(); }
4. void go() {
5. Beach[] ba = { new Beach(), new LaSelva(), (Beach) new LaSelva() };
6. for(Beach b: ba) System.out.print(b.getBeach().s + " ");
7. }
8. LaSelva getBeach() { return this; }
9. }
10. class Beach {
11. String s;
12. Beach() { s = "Beach"; }
13. Beach getBeach() { return this; }
14. }
What is the result?
A. Beach LaSelva Beach
B. Beach LaSelva LaSelva
C. Beach LaSelva followed by an exception.
D. Compilation fails due to an error at line 5.
E. Compilation fails due to an error at line 6.
F. Compilation fails due to an error at line 8.
G. Compilation fails due to an error at line 13.
Answer (for Objective 1.4):
B is correct. Line 5 is declaring a Beach array and assigning three Beach-ish objects to it. The third object created in line 5 was created as type LaSelva, and then upcast to type Beach, but the value of its String didn’t change when it was upcast. Next, LaSelva’s overriding getBeach() method is using a legal (as of Java 5) covariant return.
A, C, D, E, F, and G are incorrect based on the above.
34. When using the java.io.Console class, which are true? (Choose all that apply.)
A. Objects of type java.io.Console are created using a constructor from the same class.
B. Objects of type java.io.Console are created using a method from the java.io.File class.
C. Objects of type java.io.Console are created using a method from the java.lang.System class.
D. Objects of type java.io.Console are created using a method from the java.lang.Object class.
E. The method(s) designed to read passwords can optionally disable the echoing of user input.
F. The method(s) designed to read passwords return a char[].
Answer (for Objective 3.2):
C and F are correct.
A, B, and D describe nonexistent approaches. E is incorrect because the readPassword() methods always disable the echoing of user input.
35. Given:
3. public class Stealth {
4. public static void main(String[] args) {
5. Integer i = 420;
6. Integer i2;
7. Integer i3;
8. i2 = i.intValue();
9. i3 = i.valueOf(420);
10. System.out.println((i == i2) + " " + (i == i3));
11. } }
What is the result?
A. true true
B. true false
C. false true
D. false false
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 7.6):
D is correct. In this code, lines 8 and 9 each create a new Integer object, and == tests whether two references refer to the same object.
A, B, C, E, and F are incorrect based on the above.
36. Given:
2. import java.io.*;
3. interface Risky {
4. String doStuff() throws Exception;
5. Risky doCrazy();
6. void doInsane();
7. }
8. class Bungee implements Risky {
9. public String doStuff() throws IOException {
10. throw new IOException();
11. }
12. public Bungee doCrazy() { return new Bungee(); }
13. public void doInsane() throws NullPointerException {
14. throw new NullPointerException();
15. } }
What is the result? (Choose all that apply.)
A. Compilation succeeds.
B. The Risky interface will not compile.
C. The Bungee.doStuff() method will not compile.
D. The Bungee.doCrazy() method will not compile.
E. The Bungee.doInsane() method will not compile.
Answer (for Objective 1.2):
A is correct, the code is all legal. It’s okay for an interface method to declare an exception. It’s okay for an implementing method to throw either a narrower exception or runtime exception. Finally, it’s okay for an implementing method to use a covariant return (as in line 12).
B, C, D, and E are incorrect based on the above.
37. Given that IllegalArgumentException extends RuntimeException, and given:
11. static String s = "";
12. public static void main(String[] args) {
13. try { doStuff(); }
14. catch (Exception ex) { s += "c1 "; }
15. System.out.println(s);
16. }
17. static void doStuff() throws RuntimeException {
18. try {
19. s += "t1 ";
20. throw new IllegalArgumentException();
21. }
22. catch (IllegalArgumentException ie) { s += "c2 "; }
23. throw new IllegalArgumentException();
24. }
What is the result?
A. c1 t1 c2
B. c2 t1 c1
C. t1 c1 c2
D. t1 c2 c1
E. Compilation fails.
F. An uncaught exception is thrown at runtime.
Answer (for Objective 2.4):
D is correct. The first exception is handled in doStuff(); the second is declared in doStuff() and handled in main().
A, B, C, E, and F are incorrect based on the above.
38. Given:
1. public class Networking {
2. public static void main(String[] args) {
3. List<Integer> i = new LinkedList<Integer>();
4. i.add(4); i.add(2); i.add(5);
5. int r = 1;
6. doStuff(r);
7. System.out.println(i.get(r));
8. }
9. static int doStuff(int x) {
10. return ++x;
11. } }
What is the result?
A. 2
B. 4
C. 5
D. Compilation fails.
E. An exception is thrown at runtime.
Answer (for Objective 7.1):
D is correct. Of course, you need to import some stuff for this program to compile. This is an easy question if you spot the problem. If you don’t, it’ll seem tricky, so watch out for these on the real exam. With the proper import statements in place, A would be correct.
A, B, C, and E are incorrect based on the above.
39. Given:
1. import java.util.*;
2. public class Unturned {
3. public static void main(String[] args) {
4. String[] towns = {"aspen", "vail", "t-ride", "dillon"};
5. MySort ms = new MySort();
6. Arrays.sort(towns, ms);
7. System.out.println(Arrays.binarySearch(towns, "dillon"));
8. }
9. static class MySort implements Comparator<String> {
10. public int compare(String a, String b) {
11. return b.compareTo(a);
12. } } }
What is the most likely result?
A. -1
B. 1
C. 2
D. 3
E. Compilation fails.
F. An exception is thrown at runtime.
Answer (for Objective 6.5):
A is correct. The binarySearch() method gives meaningful results only if it uses the same Comparator as the one used to sort the array. The static inner class is legal, and on the real exam expect to find inner classes sprinkled throughout questions that are focused on other objectives.
B, C, D, E, and F are incorrect based on the above.
40. Given:
2. class Weed {
3. protected static String s = "";
4. final void grow() { s += "grow "; }
5. static final void growFast() { s += "fast "; }
6. }
7. public class Thistle extends Weed {
8. void grow() { s += "t-grow "; }
9. void growFast() { s+= "t-fast "; }
10. }
Which are the FEWEST change(s) required for this code to compile? (Choose all that apply.)
A. s must be marked public.
B. Thistle.grow() must be marked final.
C. Weed.grow() must NOT be marked final.
D. Weed.growFast() must NOT be marked final.
E. Weed.growFast() must NOT be marked static.
F. Thistle.growFast() must be removed from the class.
Answer (for Objective 5.3):
C and F are correct. Thistle can already access s. If Weed.grow() is NOT final, then Thistle can override it. In order for Weed.growFast() to be overridden, two changes (D and E), must occur, so for this question, it would require FEWER changes to remove Thistle.growFast() and not attempt an override.
Note: We don’t like this kind of question either, but you may encounter some like it on the real exam.
A, B, D, and E are incorrect based on the above.
41. Given:
2. import java.util.regex.*;
3. public class Decaf {
4. public static void main(String[] args) {
5. Pattern p = Pattern.compile(args[0]);
6. Matcher m = p.matcher(args[1]);
7. while(m.find())
8. System.out.print(m.group() + " ");
9. } }
And the three command-line invocations:
I. java Decaf "0([0-7])?" "1012 0208 430"
II. java Decaf "0([0-7])*" "1012 0208 430"
III. java Decaf "0([0-7])+" "1012 0208 430"
Which are true? (Choose all that apply.)
A. All three invocations will return valid octal numbers.
B. None of the invocations will return valid octal numbers.
C. Only invocations II and III will return valid octal numbers.
D. All three invocations will return the same set of valid octal numbers.
E. Of those invocations that return only valid octal numbers, each invocation will return a different set of valid octal numbers.
Answer (for Objective 3.4):
A and E are correct. The three invocations will return:
I. - 01 02 0 0
II. - 012 020 0
III. - 012 020
Of course, the key to this question is to remember how the three quantifiers (?, *, and +) work.
B, C, and D are incorrect based on the output given above.
42. Given:
1. class Locker extends Thread {
2. private static Thread t;
3. public void run() {
4. if(Thread.currentThread() == t) {
5. System.out.print("1 ");
6. synchronized(t) { doSleep(2000); }
7. System.out.print("2 ");
8. } else {
9. System.out.print("3 ");
10. synchronized(t) { doSleep(1000); }
11. System.out.print("4 ");
12. }
13. }
14. private void doSleep(long delay) {
15. try { Thread.sleep(delay); } catch(InterruptedException ie) { ; }
16. }
17. public static void main(String args[]) {
18. t = new Locker();
19. t.start();
20. new Locker().start();
21. } }
Assuming that sleep() sleeps for about the amount of time specified in its argument, and that all other code runs almost instantly, which are true? (Choose all that apply.)
A. Compilation fails.
B. An exception could be thrown.
C. The code could cause a deadlock.
D. The output could be 1 3 4 2
E. The output could be 1 3 2 4
F. The output could be 3 1 4 2
G. The output could be 3 1 2 4
Answer (for Objective 4.3):
D, E, F, and G are correct. When one thread prints "1", the other thread prints "3" and then either thread could hold the monitor lock of "t". The other thread will wait until the lock is released and both threads will continue to normal completion.
A, B, and C are incorrect based on the above.
43. Fill in the blanks using the fragments below, so that the code compiles and produces the output: "1 3 2 3 2 "
Note: You might not need to fill in all of the blanks. Also, you won’t use all of the fragments, and each fragment can be used only once.
Code:
Fragments:
44. Given:
2. public class Later {
3. public static void main(String[] args) {
4. boolean earlyExit = new Later().test1(args);
5. if(earlyExit) assert false;
6. new Later().test2(args);
7. }
8. boolean test1(String[] a) {
9. if (a.length == 0) return false;
10. return true;
11. }
12. private void test2(String[] a) {
13. if (a.length == 2) assert false;
14. } }
Which are true? (Choose all that apply.)
A. Compilation fails.
B. The assertion on line 5 is appropriate.
C. The assertion on line 13 is appropriate.
D. "java -ea Later" will run without error.
E. "java -ea Later x" will run without error.
F. "java -ea Later x y" will run without error.
G. "java -ea Later x y z" will run without error.
Answer (for Objective 2.3):
D is correct. This invocation will run without error.
A, B, and C are incorrect because the code compiles, and neither assertion is appropriate because ultimately they are testing the args of main(). E, F, and G are incorrect. Each will throw an AssertionError.
45. Given:
343. String s = "1234";
344. StringBuilder sb =
345. new StringBuilder(s.substring(2).concat("56").replace("7","6"));
346. System.out.println(sb.append("89").insert(3,"x"));
What is the result?
A. 34×5689
B. 345×689
C. 345×789
D. 23×45689
E. 23×45789
F. Compilation fails.
Answer (for Objective 3.1):
B is correct. The keys to remember are that indexes are 0-based, and that chained methods work from left to right. Also, the replace() method’s first argument is the character to be replaced, so in this case the replace() invocation has no effect on the StringBuilder.
A, C, D, E, and F are incorrect based on the above.
46. Given the following pseudo-code design for a new accounting system:
class Employee
maintainEmployeeInfo()
connectToRDBMS()
class Payroll
setStateTaxCodes()
findEmployeesByState()
class Utilities
getNetworkPrinter()
Assuming the class and method names provide good definitions of their own functionalities, which are probably true? (Choose all that apply.)
A. These classes appear to have low cohesion.
B. These classes appear to have high cohesion.
C. These classes appear to have weak validation.
D. These classes appear to have strong validation.
E. These classes appear to have weak encapsulation.
F. These classes appear to have strong encapsulation.
Answer (for Objective 5.1):
A and E are correct. Although somewhat subjective, A is correct because a method like connectToRDBMS() seems better placed in a utility class. As it stands, it makes the Employee class have low cohesion. E is probably correct because the findEmployeesByState() method should probably be placed in the Employee class. As it stands, the location of this method doesn’t absolutely predict weak encapsulation, but it seems a likely outcome.
B and F are incorrect based on the above. C and D are incorrect because there is no way to determine the degree of validation based on the data provided.
47. Given:
2. class Dog {
3. void makeNoise() { System.out.print("bark "); }
4. static void play() { System.out.print("catching "); }
5. }
6. class Bloodhound extends Dog {
7. void makeNoise() { System.out.print("howl "); }
8. public static void main(String[] args) {
9. new Bloodhound().go();
10. super.play();
11. super.makeNoise();
12. }
13. void go() {
14. super.play();
15. makeNoise();
16. super.makeNoise();
17. } }
What is the result? (Choose all that apply.)
A. catching howl bark catching bark
B. catching howl howl catching howl
C. catching howl bark, then an exception.
D. Compilation fails due to an error on line 10.
E. Compilation fails due to an error on line 11.
F. Compilation fails due to an error on line 14.
Answer (for Objective 5.4):
D and E are correct. Remember "super" is an instance variable, so it CANNOT be used from the static context of main().
A, B, C, and F are incorrect based on the above.
48. Given:
3. public class Baskin {
4. public static void main(String[] args) {
5. int i = 4;
6. int j = 1;
7.
8. assert(i > Integer.valueOf(args[0]));
9. assert(j > Integer.valueOf(args[0])): "error 1";
10. assert(j > i): "error 2": "passed";
11. } }
And, if the code compiles, given the following two command-line invocations:
I. java -ea Baskin 2
II. java -ea Baskin 0
Which are true? (Choose all that apply.)
A. Compilation fails.
B. Invocations I and II will throw an AssertionError that will add String data to the program’s execution log.
C. Invocations I and II will throw an AssertionError that will add String data to the program’s stack trace.
D. Not all of the assert statements use assertions appropriately.
Answer (for Objective 2.3):
A and D are correct. The syntax on line 10 is invalid and will not compile. The assert statements on lines 8 and 9 are testing the arguments of a public method, which is considered an inappropriate use of assertions. If the syntax on line 10 was fixed, then option C would be correct.
B and C are incorrect based on the above.
49. Given:
1. import java.util.*;
2. class Priorities {
3. public static void main(String[] args) {
4. PriorityQueue toDo = new PriorityQueue();
5. toDo.add("dishes");
6. toDo.add("laundry");
7. toDo.add("bills");
8. toDo.offer("bills");
9. System.out.print(toDo.size() + " " + toDo.poll());
10. System.out.print(" " + toDo.peek() + " " + toDo.poll());
11. System.out.println(" " + toDo.poll() + " " + toDo.poll());
12. } }
What is the result?
A. 3 bills dishes laundry null null
B. 3 bills bills dishes laundry null
C. 3 dishes dishes laundry bills null
D. 4 bills bills dishes laundry null
E. 4 bills bills bills dishes laundry
F. 4 dishes laundry laundry bills bills
G. Compilation fails.
H. An exception is thrown at runtime.
Answer (for Objective 6.2):
E is correct. The add() and offer() methods have the same functionality, and it’s okay for PriorityQueues to have duplicate elements. Remembering that PriorityQueues are sorted, the poll() method removes the first element in the queue and returns it. The peek() method returns the first element from the queue but does NOT remove it.
A, B, C, D, F, G, and H are incorrect based on the above.
50. Given that the working directory is bigApp, and the following directory structure:
And the code:
1. public class BigAppClass2 { int doMore() { return 17; } }
And the following command-line invocations:
I. javac -d source/com/wickedlysmart/BigAppClass2.java
II. javac -d classes source/com/wickedlysmart/BigAppClass2.java
III. javac -d classes/com/wickedlysmart source/com/wickedlysmart/BigAppClass2.java
Which are true? (Choose all that apply.)
A. Invocation I will compile the file and place the .class file in the bigApp directory.
B. Invocation II will compile the file and place the .class file in the classes directory.
C. Invocation I will compile the file and place the .class file in the wickedlysmart directory.
D. Invocation II will compile the file and place the .class file in the wickedlysmart directory.
E. Invocation III will compile the file and place the .class file in the wickedlysmart directory.
Answer (for Objective 7.2):
B and E correctly describe the results that the -d option will produce. Note that the BigAppClass2 class doesn’t have a package statement.
A and C will not compile. Option D is incorrect based on the above.
51. Given:
1. class Contact {
2. String doStuff() { return "howdy "; }
3. }
4. class Supplier extends Contact {
5. String doStuff() { return "send money "; }
6. public static void main(String[] args) {
7. Supplier s1 = new Supplier();
8. Contact c3 = new Contact();
9. Contact c1 = s1;
10. Supplier s2 = (Supplier) c1;
11. Supplier s3 = (Supplier) c3;
12. Supplier s4 = new Contact();
13. } }
Which are true? (Choose all that apply.)
A. Compilation succeeds.
B. The code runs without exception.
C. If the line(s) of code that do NOT compile (if any) are removed, the code runs without exception.
D. If the line(s) of code that do NOT compile (if any) are removed, the code throws an exception at runtime.
Answer (for Objective 5.2):
D is correct. Once line 12 is removed, the code will compile but throw a ClassCastException at line 11.
A, B, and C are incorrect based on the above.
52. Given that Integer.parseInt() throws NumberFormatException, and given:
3. public class Ladder {
4. public static void main(String[] args) {
5. try {
6. System.out.println(doStuff(args));
7. }
8. catch (Exception e) { System.out.println("exc"); }
9. doStuff(args);
10. }
11. static int doStuff(String[] args) {
12. return Integer.parseInt(args[0]);
13. } }
And, if the code compiles, given the invocation:
java Ladder x