In the code below, inter is an interface which has a method add(int i1,int i2). The implementation is done in Impl class.

 Interface code(inter.java)public interface inter{  public int add(int i1,int i2);}Class Code(Impl.java)public class Impl{ public Impl()  { // implement the interface by anonymous innerclass    inter i=new inter()     {	  public int add(int i1,int i2)           {	    return i1+i2;	   }     };         System.out.println(i.add(4,5));      } //end of constructor  public static void main(String a[])  {	  ser d =new ser();  }}//end of class

Thus, the interface is implemented in Impl class without an implements keyword.