为什么我们不能在静态方法中使用'this'关键字 [英] Why can't we use 'this' keyword in a static method

问题描述

class Sub {
    static int y;
    public static void foo() {
         this.y = 10;
    }
}

我明白这个表示调用该方法的对象，并且静态方法未绑定到任何对象。但在上述情况下，变量y也是静态的。

I understand that this represents the object invoking the method and that static methods are not bound to any object. But in the above mentioned case, the variable y is also static.

如果我们可以在类对象上调用静态方法，为什么我们不能允许静态方法设置类的静态变量。

If we can invoke static method on class object, why can't we allow static methods to set the static variables of the class.

这个额外约束的目的是什么？

What is the purpose of this additional constraint?

推荐答案

因为这个是指对象实例。在调用静态方法时没有对象实例。但是当然你可以访问静态字段（只有静态字段！）。只需使用

Because this refers to the object instance. There is no object instance in a call of a static method. But of course you can access your static field (only the static ones!). Just use

class Sub {
    static int y;
    public static void foo() {
         y = 10;
    }
}

如果你想确保得到静态字段 y 而不是具有相同名称的某个局部变量，请使用类名来指定：

If you want to make sure you get the static field y and not some local variable with the same name, use the class name to specify:

class Sub {
    static int y;
    public static void foo(int y) {
         Sub.y = y;
    }
}

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