享元模式

享元模式听名字就知道是共享一个东西，为了节省内存嘛。那么它和单例模式有什么不同呢？单例模式就一个对象，而享元模式是一组对象，共享的是相同的对象。没错，我们的String就用的享元模式，下面我们代码实现：

public class Flyweight {
    interface 字符串 {
        void operation();
    }

    public static class 包装字符串 implements 字符串 {//可以有斜体字符串，但重点不是这
        private String string;

        public 包装字符串(String str) {
            string = str;
        }

        public void operation() {
            System.out.println(this.hashCode());
        }
    }

    public static class FlyweightFactory {  //这里看出工厂模式的好处了吧

        private Hashtable<String, 字符串> flyweights = new Hashtable<>();

        public FlyweightFactory() {
        }

        public 字符串 getFlyWeight(String obj) {
            字符串 flyweight = flyweights.get(obj);
            if (flyweight == null) {//不同的String才产生新的对象
                flyweight = new 包装字符串(obj);
                flyweights.put(obj, flyweight);
            }
            return flyweight;
        }
    }

    public static void main(String[] args) {
        FlyweightFactory factory = new FlyweightFactory();
        字符串 fly1 = factory.getFlyWeight("Google");
        字符串 fly2 = factory.getFlyWeight("Qutr");
        字符串 fly3 = factory.getFlyWeight("Google");
        fly1.operation();
        fly2.operation();
        fly3.operation();
    }
}
输出：
2133927002
1836019240
2133927002

觉得容易理解的话面向对象的23种设计模式点这里