Java 中的实例变量是什么？

实例变量是在类内部声明的变量，但在方法外部声明的变量：如下所示：

class IronMan {

    /** These are all instance variables **/
    public String realName;
    public String[] superPowers;
    public int age;

    /** Getters and setters here **/
}

现在，这个铁人三项类可以在另一个类中实例化以使用这些变量。像这样：

class Avengers {

    public static void main(String[] a) {
        IronMan ironman = new IronMan();
        ironman.realName = "Tony Stark";
        // or
        ironman.setAge(30);
    }

}

这就是我们使用实例变量的方式。无耻的插头：这个例子是从这本免费的电子书中拉出来的。

实例变量是类实例的成员（即，与使用 a 创建的内容相关联）的变量，而类变量是类本身的成员。new

类的每个实例都有自己的实例变量副本，而每个静态（或类）变量中只有一个与类本身相关联。

类变量和实例变量之间有什么区别？

此测试类说明了其区别：

public class Test {
   
    public static String classVariable = "I am associated with the class";
    public String instanceVariable = "I am associated with the instance";
    
    public void setText(String string){
        this.instanceVariable = string;
    }
    
    public static void setClassText(String string){
        classVariable = string;
    }
    
    public static void main(String[] args) {
        Test test1 = new Test();
        Test test2 = new Test();
        
        // Change test1's instance variable
        test1.setText("Changed");
        System.out.println(test1.instanceVariable); // Prints "Changed"
        // test2 is unaffected
        System.out.println(test2.instanceVariable); // Prints "I am associated with the instance"
        
        // Change class variable (associated with the class itself)
        Test.setClassText("Changed class text");
        System.out.println(Test.classVariable); // Prints "Changed class text"
        
        // Can access static fields through an instance, but there still is only one
        // (not best practice to access static variables through instance)
        System.out.println(test1.classVariable); // Prints "Changed class text"
        System.out.println(test2.classVariable); // Prints "Changed class text"
    }
}