享元模式

什么是享元模式

将对象中有共同特性的属性提取出来进行共享，避免对象的重复创建从而减少内存的消耗

示例图

图片.png

示例场景

6个用户分别购买不同类别的水果，有苹果 梨 橙子，虽然购买了6次但是实例化的水果类别为3种。（内部状态：可以共享的属性为水果类别 外部状态：不可共享的属性为用户名称）

示例代码

1.创建Fruits抽象类

public abstract class Fruits {
    public abstract  void buyFruits(User user);
}

2.创建ConcreteFruits具体水果实现类

public class ConcreteFruits extends  Fruits {
    private String fruitsName;


    public ConcreteFruits(String fruitsName) {
        this.fruitsName = fruitsName;
    }

    @Override
    public void buyFruits(User user) {
        System.out.println(user.getName()+"购买了"+fruitsName);
    }
}

3.创建user用户信息类

public class User {
    private String name;

    public User(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

4.创建FruitsFactory水果工厂类

public class FruitsFactory {
    private HashMap<String, ConcreteFruits> map = new HashMap<>();

    //将内部状态(水果类别)存入map中进行共享
    public Fruits getConcreteFruits(String fruitsName){
        if(!map.containsKey(fruitsName)){
            map.put(fruitsName,new ConcreteFruits(fruitsName));
        }
        return map.get(fruitsName);
    }
    //获取水果类别个数
    public int getNumber(){
        return map.size();
    }
}

5.创建Client启动类

public class Client {
    public static void main(String[] args) {
        FruitsFactory fruitsFactory = new FruitsFactory();
        Fruits fruits1 =  fruitsFactory.getConcreteFruits("苹果");
        fruits1.buyFruits(new User("小天"));
        Fruits fruits2 =  fruitsFactory.getConcreteFruits("梨");
        fruits2.buyFruits(new User("小张"));
        Fruits fruits3 =  fruitsFactory.getConcreteFruits("苹果");
        fruits3.buyFruits(new User("小文"));
        Fruits fruits4 =  fruitsFactory.getConcreteFruits("橙子");
        fruits4.buyFruits(new User("小红"));
        Fruits fruits5 =  fruitsFactory.getConcreteFruits("苹果");
        fruits5.buyFruits(new User("小兰"));
        Fruits fruits6 =  fruitsFactory.getConcreteFruits("橙子");
        fruits6.buyFruits(new User("小兵"));
        int number = fruitsFactory.getNumber();
        System.out.println("水果类别个数是:"+number+"个");
    }
}

5.运行结果

图片.png