Java中的对象变量与类变量 [英] Object Variables vs Class Variables in Java

问题描述

我正在学习Java，我不理解对象变量和类变量之间的区别。我所知道的是，为了使它成为一个类变量，你必须先用静态语句声明它。
谢谢！

I am in the process of learning Java and I don't understand the difference between Object Variables and Class Variable. All I know is that in order for it to be a Class Variable you must declare it first with the static statement. Thanks!

推荐答案

在Java（以及一般的OOP）中，对象有两种字段（变量） 。

In Java (and in OOP in general) the objects have two kinds of fields(variable).

实例变量（或对象变量）是属于对象特定实例的字段。

Instance variables(or object variable) are fields that belong to a particular instance of an object.

静态变量（或类变量）对同一个类的所有实例都是通用的。

Static variables (or class variable) are common to all the instances of the same class.

这是一个例子：

public class Foobar{
    static int counter = 0 ; //static variable..all instances of Foobar will share the same counter and will change if such is done
    public int id; //instance variable. Each instance has its own id
    public Foobar(){
        this.id = counter++;
    }
}

用法：

Foobar obj1 = new Foobar();
Foobar obj2 = new Foobar();
System.out.println("obj1 id : " + obj1.id + " obj2.id "+ obj2.id + " id count " + Foobar.counter);

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