外层阶级呼唤内层阶级的方式 [英] Way to call inner class by outer class

问题描述

我知道要实例化一个成员内部类，您有两个不同的构造函数:

I know that to instantiate a member inner class, you have two different constructors:

第一:

Outer out = new Outer();
Outer.Inner in = out.new Inner();

第二:

Outer.Inner in = new Outer().new Inner();

现在，我不知道为什么编译此代码:

Now, I don't know why this code compiles:

public class Outer {

    private String greeting="Hi";

    protected class Inner {
        public int repeat=3;

        public void go() {
            for (int i =0; i<repeat; i++) {
                System.out.println(greeting);
            }
        }
    }

    public void callInner() {
        Inner in = new Inner(); //in my opinion the correct constructor is Outer.Inner in = new Inner()
        in.go();
    }

    public static void main(String[] args) {
        Outer out = new Outer();
        out.callInner();

    }
}

为什么要编译?

非常感谢！

推荐答案

在外部范围内(实例方法内部)实例化 Inner 时，您会执行无需像在您的示例中那样显式实例化引用外部类别:

As you are instantiating Inner within the scope of Outer (inside an instance method), you do not need to explicitly instantiate referencing the Outer clas, like in your example:

Outer.Inner in = new Outer().new Inner();

仅引用 Inner 即可实例化:

 Inner in = new Inner();

这适用于类中的所有实例方法，只要它们不是静态的.

This applies to all instance methods within a class, as long as they are not static.

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