public class OuterClass {
    public String outerClassName = "outerClass's name";

    public void getNestedClassName() {
        String staticString = NestedStaticClass.staticString;
        //无法直接调用非静态内部类的变量
        //String str = NestedClass.nestedClassName;
    }

    public NestedClass getNestedClass() {
        //可以直接new
        return new NestedClass();
    }


    class NestedClass {
        public String nestedClassName = "nestedClass's name";

        public void printOuterClassName() {
            //可以直接调用外部类的对象
            System.out.println(outerClassName);
        }

        public OuterClass getOuter() {
            //返回外部类实例
            return OuterClass.this;
        }
    }

    static class NestedStaticClass {
        public String nestedClassName = "NestedStaticClass's name";
        public static String staticString = "staticString";

        public void printOuterClassName() {
            //error 不可以直接调用外部类的对象
            //System.out.println(outerClassName);
        }

        //error 无法返回外部类实例
//        public OuterClass getOuter(){
//            return OuterClass.this;
//        }
    }
}
class Test{
    public static void main(String[] args) {
        //不允许直接通过new的方式创建OuterClass.NestedClass
        //OuterClass.NestedClass nestedClass1 = new OuterClass.NestedClass();

        //只能通过外部类的实例创建内部类
        OuterClass outerClass = new OuterClass();
        //通过方法返回内部类实例
        OuterClass.NestedClass nestedClass = outerClass.getNestedClass();
        //通过.new关键字
        OuterClass.NestedClass nestedClass1 = outerClass.new NestedClass();

        //通过内部类实例获取外部类实例
        System.out.println(nestedClass1.getOuter().outerClassName);
        nestedClass.printOuterClassName();

        String staticString = OuterClass.NestedStaticClass.staticString;
        OuterClass.NestedStaticClass nestedStaticClass = new OuterClass.NestedStaticClass();
        System.out.println(nestedStaticClass.nestedClassName);

    }
}