interface vs class itself

gistfile1.java

public class Test {
	public static class A {}
	public static class B extends A {}
	public static class C extends A {}

	public interface Hello {
		void hello(A a);
	}

	public static class Tester implements Hello {

		@Override
		public void hello(A a) {
			System.out.println( "Hello, A" );
		}

		public void hello(B b) {
			System.out.println( "Hello, B" );
		}

		public void hello(C c) {
			System.out.println( "Hello, C" );
		}
	
	}

	public static class Tester2 implements Hello {

		@Override
		public void hello(A a) {
			myHello(a);
		}

		public void myHello(A a) {
			System.out.println( "Hello, A" );	
		}
	
		public void myHello(B b) {
			System.out.println( "Hello, B" );	
		}
	
		public void myHello(C c) {
			System.out.println( "Hello, C" );	
		}
	}

	public static void main(String[] args) {
		System.out.println("Interface:");
		Hello h = new Tester();
		h.hello( new A() );
		h.hello( new B() );
		h.hello( new C() );

		System.out.println("Class:");
		Tester t = new Tester();
		t.hello( new A() );
		t.hello( new B() );
		t.hello( new C() );

		System.out.println("Class2:");
		Tester2 t2 = new Tester2();
		t2.hello( new A() );
		t2.hello( new B() );
		t2.hello( new C() );
	}
}