Two ways that a class can implement multiple interfaces : Nested Classes « Class Definition « Java Tutorial

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

interface A {
}

interface B {
}

class X implements A, B {
}

class Y implements A {
  B makeB() {
    // Anonymous inner class:
    return new B() {
    };
  }
}

public class MainClass {
  static void takesA(A a) {
  }

  static void takesB(B b) {
  }

  public static void main(String[] args) {
    X x = new X();
    Y y = new Y();
    takesA(x);
    takesA(y);
    takesB(x);
    takesB(y.makeB());
  }
}