Nesting a class within a method : Nested Classes « Class Definition « Java Tutorial

1. Java Tutorial
2. Class Definition
3. Nested Classes

public class MainClass {
  public A dest(String s) {
    class B implements A {
      private String label;

      private B(String whereTo) {
        label = whereTo;
      }

      public String readLabel() {
        return label;
      }
    }
    return new B(s);
  }

  public static void main(String[] args) {
    MainClass p = new MainClass();
    A d = p.dest("A");
  }
}

interface A {
  String readLabel();
}