内部类

https://www.liaoxuefeng.com/wiki/1252599548343744/1376414781669409

Java的内部类可分为Inner Class、Anonymous Class和Static Nested Class三种：

• Inner Class和Anonymous Class本质上是相同的，都必须依附于Outer Class的实例，即隐含地持有Outer.this实例，并拥有Outer Class的private访问权限；
• Static Nested Class是独立类，但拥有Outer Class的private访问权限。

public class Main {
    public static void main(String[] args) {
        Outer outer = new Outer("Nested"); // 实例化一个Outer
        Outer.Inner inner = outer.new Inner(); // 实例化一个Inner
        inner.hello();
    }
}
class Outer {
    private String name;
    Outer(String name) {
        this.name = name;
    }
    class Inner {
        void hello() {
            System.out.println("Hello, " + Outer.this.name);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Outer.StaticNested sn = new Outer.StaticNested();
        sn.hello();
    }
}
class Outer {
    private static String NAME = "OUTER";
    private String name;
    Outer(String name) {
        this.name = name;
    }
    static class StaticNested {
        void hello() {
            System.out.println("Hello, " + Outer.NAME);
        }
    }
}