overridingtest2.java

java程序设计 清华出版社 孙燮华老师编写的程序源代码

//overridingTest2.java
class ClassA{
  protected int m;
  protected int n;
  
  void F(){
  	m=66;
  	System.out.println("Now in ClassA.F()"); 
  }
  void G(){
  	n=88;
  	System.out.println("Now in ClassA.G()");
  }
  public String toString(){
  	return new String("{ m = " + m + ", n = " + n + "}");
  }
}

class ClassB extends ClassA{
  private double n;        //覆盖了域ClassA.n
  
  void G(){                //覆盖了域ClassA.G()
    n=3.1415926535897932;
    System.out.println("Now in ClassB.G()");
  }
  
  public String toString(){//覆盖了域ClassA.toString()
  	return new String("{ m = "+ m + ", n = " + n + "}");
  }
}

class overridingTest2{
  public static void main(String[] args){
  	ClassA a=new ClassA();
  	a.F();
  	a.G();
  	System.out.println(a.toString());
  	ClassA b=new ClassB();
  	b.F();
  	b.G();
  	System.out.println(b.toString());
  }
}