继承接口

父类

public class Father {
 private int money;
 int weight;
 int getWeight() {
  return weight;
 }
 
 protected void setWeight(int w) {
  weight = w;
 }
}

子类

public class Son extends Father {
 
 String hand;
 public void setHand(String hand) {
  this.hand = hand;
 }
 
 String getHand() {
  return hand;
 }

}

public class Grandson extends Son{
 
 String foot;
 public void setFoot(String foot) {
  this.foot= foot;
  
 }
 
 String getfoot() {
  return foot;
 }

}

public class Example5_1 {

 public static void main(String[] args) {
  Son son = new Son();
  Grandson grandson = new Grandson();
  Father father = new Father();
  son.setWeight(62);
  son.setHand("一双大手");
  grandson.setWeight(29);
  grandson.setHand("一双小手");
  grandson.setFoot("一双小脚");
  
  System.out.println("儿子的重量：" + son.getWeight());
  System.out.println("孙子的重量：" + grandson.getWeight());
  System.out.println("儿子的手：" + son.getHand());
  System.out.println("孙子的手：" + grandson.getHand());
  System.out.println("孙子的脚：" + grandson.getfoot());
 }

}

输出的结果是：

儿子的重量：62
孙子的重量：29
儿子的手：一双大手
孙子的手：一双小手
孙子的脚：一双小脚