无法在静态方法中声明静态变量 [英] Unable to declare static variable inside of static method

问题描述

class Foo {
    public Foo() { }
}

class Bar {
    static Foo foo = new Foo(); // This is legal...

    public static void main(String[] args) { 
        static int a = 0; // ... But why this is not?
    }
}

为什么我们不能在里面声明一个静态变量一个静态函数？

Why can't we declare a static variable inside of a static function?

推荐答案

你必须使静态最终静态或删除 static 。

在Java中，static表示它是类的变量/方法，它属于整个班级，但不是其中一个特定的对象。这意味着static关键字只能在类范围中使用。

In Java, static means that it's a variable/method of a class, it belongs to the whole class but not to one of its certain objects. This means that static keyword can be used only in a 'class scope'.

通常，在C中，您可以静态分配本地范围的变量。不幸的是，这不是Java直接支持的。但是你可以通过使用嵌套类来实现相同的效果。

Generally, in C, you can have statically allocated locally scoped variables. Unfortunately this is not directly supported in Java. But you can achieve the same effect by using nested classes.

例如，允许使用以下内容，但这是一个糟糕的工程，因为x的范围远大于它需要是。此外，两个成员之间存在非明显的依赖关系（x和getNextValue）。

For example, the following is allowed but it is bad engineering, because the scope of x is much larger than it needs to be. Also there is a non-obvious dependency between two members (x and getNextValue).

static int x = 42;
public static int getNextValue() {
    return ++x;
}

人们真的想做以下事情，但这不合法：

One would really like to do the following, but it is not legal:

public static int getNextValue() {
    static int x = 42;             // not legal :-(
    return ++x;
}

但是你可以这样做，

public static class getNext {
    static int x = 42; 
    public static int value() {
        return ++x;
    }
}

以牺牲丑陋为代价更好的工程设计。

It is better engineering at the expense of some ugliness.

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