How are Anonymous inner classes used in Java?

Question

What is the use of anonymous classes in Java? Can we say that usage of anonymous class is one of the advantages of Java?

Answer 1

Anonymous inner class is used in following scenario:

1.)For Overriding(Sub classing) ,When class definition is not usable except current case:

class A{
   public void methodA() {
      System.out.println("methodA");
    }
}
class B{
    A a = new A() {
     public void methodA() {
        System.out.println("anonymous methodA");
     }
   };
}

2.)For implementing an interface,When implemention of interface is required only for current case:

interface interfaceA{
   public void methodA();
}
class B{
   interfaceA a = new interfaceA() {
     public void methodA() {
        System.out.println("anonymous methodA implementer");
     }
   };
}

3.)Argument Defined Anonymous inner class:

 interface Foo {
   void methodFoo();
 }
 class B{
  void do(Foo f) { }
}

class A{
   void methodA() {
     B b = new B();
     b.do(new Foo() {
       public void methodFoo() {
         System.out.println("methodFoo");
       } 
     });
   } 
 }