结构型模式 --- 享元模式

通过共享的方式减少对象的创建

// 享元类
package flyweight;

import java.util.HashMap;
import java.util.Map;

public class FlyWeight {
    private static final Map<String, String> POOL = new HashMap<String, String>();
    
    
    public static String getVal(String aaa) {
        if (POOL.containsKey(aaa)) {
            
            System.out.println("共享对象");
            
            return POOL.get("aaa");
        } else {
            String string = new String( aaa + "Val");
            System.out.println("新建对象");
            POOL.put(aaa, string); //aaaVal 可以是个自定义类 aaaVal是为了演示随便写的
            return string;
        }
    }
}

// 测试类
package flyweight;

public class Client {
    public static void main(String[] args) {
        FlyWeight.getVal("aaa");// 新建对象
        FlyWeight.getVal("bbb");// 新建对象
        FlyWeight.getVal("aaa");// 共享对象
        FlyWeight.getVal("ccc");// 新建对象
        
    }
}