为什么外部类在Java中不是静态的？ [英] Why outer classes are not static in java?

问题描述

在java中，外部类可以是public，final，default或abstract。
为什么不像

In java, An outer class may be public, final, default or abstract. Why not Static like

Static static class MyClass {}

推荐答案

外部类已经是隐式静态的。

An outer class is already implicitly static.

非静态嵌套类意味着内部类隐含地引用其父类。

Non-static nested class (= inner class) means thats the inner class implicitly has a reference to its parent class.

这就是为什么对于嵌套类，你可以区分静态和非静态。这对外部类没有意义。

That's why, for nested class, you can distinguish between static and non-static. This does not make sense for outer classes.

这里是一个例子来了解静态/非静态嵌套类之间的区别。你应该明白为什么在外部类中没有意义。

Here is an example to understand the difference between static/non-static nested class. You should understand why it does not make sense in an outer class.

public class MyClass {

  private String anAttributeOfMyClass;

  private /*static*/ class MyInnerClass {

    public void foo() {
      /*
       * Here, I can access the attribute of the parent class
       * because I implicitly have a reference to it.
       * Try to make the nested class static an see the difference.
       */
      anAttributeOfMyClass.trim();
    }
  }

}

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