重复利用对象，常与组合模式共用，组成复杂模块
（Word文档，String，游戏地图坐标）
代码结构
源码
package com.myspringboot.shejimoshi.xiangyuan;
public class StringTest {
public static void main(String[] args) {
// 字符串常量池
String s1 = "a";
String s2 = "a";
String s3 = new String("a");
String s4 = new String("a");
System.out.println(s1 == s2); //true
System.out.println(s1 == s3); //false
System.out.println(s3 == s4); //false
System.out.println(s3.intern() == s1); //true
System.out.println(s3.intern() == s4.intern()); //true
String ss1 = "abc";
String ss2 = "abc";
String ss3 = new String("abc");
String ss4 = new String("abc");
System.out.println(ss1 == ss2); //true
System.out.println(ss1 == ss3); //false
System.out.println(ss3 == ss4); //false
System.out.println(ss3.intern() == ss1); //true
System.out.println(ss3.intern() == ss4.intern()); //true
}
}
