Question

public class A {
  protected int x;
  public A(int x) { this.x = x; }
  public void g() { System.out.println(x); }
  public void h() { System.out.println(x + 10); }
}
public class B {
  public void f() {
  (new A(2) {
    public void g() {
      h();
    }
   }).g();
  }
}

public static void main(String[] args) {
  new B().f();
}

Can some body help me understanding this line in code:

new A(2) { public void g() {h();} }).g();

I don’t understand if he define a anonymous class here with A ?? and how in the anonymous he can refer to A.h() ?

Answer 1

He creates an anonymous class and also overwrites g(). It’s the same like when you use Runnable and override run.

(new A(2) { public void g() {h();} }).g();

means

class C extends A
{
    public C()
    {
        super(2);
    }

    @Override
    public void g()
    {
        this.h();
    }
}

(new C()).g();  // or C c = new C(); c.g();