A lambda expression is an anonymous function that is not declared but passed immediately as an expression.

Let's go ahead and make use of lambda expressions in our TicTacToe app. Open MainActivity.kt. In the startNewGame() function, replace the following lines of code:

cell.setOnClickListener(object : View.OnClickListener {
    override fun onClick(v: View?) {
        cellClickListener(i, j)
    }
})

Replace them with this line of code:

cell.setOnClickListener { cellClickListener(i, j) } 

In the previous lines of code, we have an anonymous object that is implementing a Java interface that has a single abstract method (onClick()). All of this can be replaced with a simple lambda expression.

Now, build and run to see the state of the app:

Let's go ahead and make use of all we've learned so far to in order complete work on the game.