如何理解java中的super [英] how to understand super in java

问题描述

遇到一个让我困惑的问题，是关键字'super'，我的测试代码是这样的:

I encountered a problem that confused me, it is the keyword 'super', my test code is like this:

package test;

public class Parent {
   private String name;

   public Parent(){
        this.name = "parent";      
   }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void showName(){
        System.out.println(this.name);
    }

}


public class Child extends Parent{

    public Child(){
        this.setName("Child");
    }

    public void showName(){
        System.out.println(super.getClass().toString());
        System.out.println(super.toString());

        super.showName();
        System.out.println(super.getName());
    }
}

public class Test {

    public static void main(String[] args) {
        Child d = new Child();
        d.showName();    
    }
}

所以结果是这样的:

class test.Child
test.Child@2207d8bb
Child
Child

我对'super'的理解是它是对当前实例的父实例的引用，所以我期望的输出就像'Parent'，从结果来看，我错了，就像当前实例调用父方法一样，并且超级"不是父实例，我的理解对吗?有没有办法让父实例只初始化子类?

my understanding about 'super' is that it is a reference to the parent instance of current instance, so my expecting output is like 'Parent', from the result , I am wrong, its like the current instance calls the parent method, and 'super' is not parent instance, is my understanding right ? and is there a way that I can get parent instance only initializing the Child class ?

推荐答案

我对'super'的理解是它是对当前实例的父实例的引用

my understanding about 'super' is that it is a reference to the parent instance of current instance

不 - 没有父实例"这样的东西.当你创建一个实例时，只会创建一个对象——一个Child的实例，它也继承了Parent的所有字段和方法.

No - there's no such thing as a "parent instance". When you create an instance, there's only one object created - an instance of Child, which inherits all the fields and methods from Parent as well.

super 有两种使用方式:

• 引用方法的超类实现，通常是在您覆盖子类中的方法时.这就是您在 Child.showName 中所做的 - 它正在调用 Parent.showName，但是 在同一个实例上(因为有 是只有一个实例)
• 从子类构造函数调用超类构造函数

• To refer to the superclass implementation of a method, typically when you've overridden the method in the subclass. This is what you're doing in Child.showName - it's calling Parent.showName, but on the same instance (because there is only one instance)
• To call a superclass constructor from a subclass constructor

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