class A {
  int i, j;
  void showij() {
    System.out.println("i and j: " + i + " " + j);
  }
}
//創建一個繼承超類A的子類B 
class B extends A {
  int k;
  void showk() {
    System.out.println("k: " + k);
  }
  void sum() {
    System.out.println("i+j+k: " + (i+j+k));
  }
}
class SimpleInheritance {
  public static void main(String args[]) {
    A superOb = new A();
    B subOb = new B();
    // The superclass may be used by itself.
    superOb.i = 10;
    superOb.j = 20;
    System.out.println("Contents of superOb: ");
    superOb.showij();
    System.out.println();
    /* The subclass has access to all public members of
     its superclass. */
    subOb.i = 7;
    subOb.j = 8;
    subOb.k = 9; 
    System.out.println("Contents of subOb: ");
    subOb.showij();
    subOb.showk();
    System.out.println();
    System.out.println("Sum of i, j and k in subOb:");
    subOb.sum();
  }
}