When the @Primary annotation is used on a bean, it becomes the primary one to be used when there is more than one candidate available to autowire a specific dependency.

In the case of the following example , there are two sorting algorithms available: QuickSort and MergeSort. If the component scan finds both of them, QuickSort is used to wire any dependencies on SortingAlgorithm because of the @Primary annotation:

    interface SortingAlgorithm { 
    } 
    @Component 
    class MergeSort implements SortingAlgorithm { 
      // Class code here 
    } 
   @Component 
   @Primary 
   class QuickSort implements SortingAlgorithm { 
     // Class code here 
   }