增强功能：不改变原有功能实现，灵活的添加新的功能

输入输出流的一套包装类，就是装饰器。

代码结构
Java设计模式：装饰器模式_包装类
源码

package com.myspringboot.shejimoshi.zhuangshiqi;

import java.io.*;

public class Main {
    public static void main(String[] args) {
        File file = new File("D:\\javatest\\1.txt");
        try (FileOutputStream fos = new FileOutputStream(file);
             OutputStreamWriter osw = new OutputStreamWriter(fos);
             BufferedWriter bw = new BufferedWriter(osw);) {
            bw.write("decorator");
            bw.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}