Java重写困惑

Question

我是 java 的新手，现在我有一个关于方法覆盖的问题:

public class maintest {
    public static void main(String[] args) {
        new Zi();
    }
}

public class Fu {

    public Fu() {
        show();
    }
    public void show() {
        System.out.println("This is from Fu show");
    }
}

public class Zi extends Fu {
    public Zi() {
        show();
        super.show();
    }

    public void show() {
        System.out.println("This is from zi show");
    }
}

当我运行这个程序时，输出是:

This is from zi show
This is from zi show
This is from Fu show

谁能给我一些关于为什么第一行输出是

的简单易懂的解释

This is from zi show

而不是

This is from Fu show

换个说法，为什么父类(super class)中的show方法被隐藏了？

Answer 1

在你的构造函数中你这样做，

public Zi() {
  super(); // <-- you didn't have this, so the compiler added it.
           // your Fu class then calls Zi's show.
           // Why? Because Zi has a method named show that override Fu's
           // show method. So the Fu constructor (when it calls show()) gets the 
           // show implementation in Zi.
  show(); // <-- first explicit show call (but the second "This is from zi show")
  super.show(); // <-- then call the Fu.show()
}