动手动脑四

Posted 2020-12-02 xrj-

1.总结父类与子类构造方法的调用关系

package test;
import java.io.*;
import javax.swing.*;
import java.awt.FlowLayout;
import java.awt.event.*;


class Grandparent 
{


    public Grandparent()
     {

            System.out.println("GrandParent Created.");
    
}


    public Grandparent(String string) 
    {

            System.out.println("GrandParent Created.String:" + string);
    
 }

}



class Parent extends Grandparent
{


    public Parent()
     {

            //super("Hello.Grandparent.");

            System.out.println("Parent Created");
    
       // super("Hello.Grandparent.");

      }

}



class Child extends Parent 
{


    public Child()
     {
    
        System.out.println("Child Created");

      }

}



public class TestFile 
{


    public static void main(String args[])
     {

            Child c = new Child();
    
  }

}

 

 构造函数为默认构造函数时，new了子类，会按照继承顺序倒着调用构造关系。

有super时，super必须写在子类构造函数的第一句，否则编译器也会报错。

2.

package test;
import java.io.*;
import javax.swing.*;
import java.awt.FlowLayout;
import java.awt.event.*;


public class  TestFile {

    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.println(new A());
    }

}

class A{}