【编程思想笔记】内部类的初始化

看编程思想有点时间了，看到了些在马士兵老师没有讲过的部分，所以打算记录一下

内部类的初始化：

.内部类的初始化和外部类的初始化略有不同，可以使用 外部类对象.new 内部类对象 创建内部类对象

package com.github.hellxz.practice10_2_2;

public class Outer {
    public String toString() {
        return "Outer class override toString() method";
    }
    class Inner{
        public String toString() {
            return "Inner class override toString() method";
        }
    }
    public static void main(String args[]) {
        //this is wrong way to create inner class instance
        //! Inner inner = new Outer.Inner();
        Outer outer = new Outer(); //create outer instance first ,cuz an inner instance must create on a outer instance
        Inner inner = outer.new Inner(); //create inner instance. 
        //the declare type also can be Outer.Inner
        Outer.Inner inner2 = outer.new Inner();
    }
}

内部类对象返回外部类对象的引用：

.使用 .this  在上边代码的基础上修改代码

package com.github.hellxz.test;

public class Outer {
    public String toString() {
        return "Outer class override toString() method";
    }
    class Inner{
        //a method to return outer class reference
        Outer outer() {
            return Outer.this;
        }
        public String toString() {
            return "Inner class override toString() method";
        }
    }
    public static void main(String args[]) {
        Outer outer = new Outer(); 
        System.out.println(outer); //show which reference
        Inner inner = outer.new Inner(); 
        System.out.println(inner); 
        // use inner class method to return outer class reference
        //! Inner inner2 = inner.outer(); //it wrong
        Outer outer2 = inner.outer();
        System.out.println(outer2);
    }
}

//output:
//Outer class override toString() method
//Inner class override toString() method
//Outer class override toString() method

 

问我为啥注释都英文，因为我这linuxmint的root用户的fcitx好像没装好。在普通用户下正常，一使用root用户就不行，百度好久也没解决，有知道解决方法的老哥评论下告知呗，小弟感激不尽！