享元模式

享元模式（Flyweight Pattern）用于减少创建对象的数量，以减少内存占用和提高性能。这种模式尝试重用现有的细粒度对象，而不是每次都重新创建新的对象。享元模式特别适用于大量相似对象的场景，这些对象的状态可以被外部状态共享。

案例

设计一个足道店，服务员可以重复提供服务

java 复制代码

public abstract class AbstractWaiter {
    Integer id;
    String name;
    boolean canService;
    public AbstractWaiter(Integer id,String name){
        this.id = id;
        this.name = name;
        canService = true;
    }
    public abstract void service();
    public abstract void end();
}

java 复制代码

public class Waiters extends AbstractWaiter{
    public Waiters(Integer id, String name) {
        super(id, name);
    }

    @Override
    public void service() {
        System.out.println(id + "：开始服务");
        this.canService = false;
    }

    @Override
    public void end() {
        System.out.println(id + "：结束服务");
        this.canService = true;
    }
}

java 复制代码

public class ZuDao {
    private Map<Integer,Waiters> poll = new HashMap<>();

    {
        Waiters zhangsan = new Waiters(1, "zhangsan");
        Waiters lisi = new Waiters(2, "lisi");
        poll.put(1,zhangsan);
        poll.put(2,lisi);
    }

    public Waiters getWaiter(Integer id){
        Waiters waiter = poll.get(id);
        if(waiter != null && waiter.canService){
            return waiter;
        }
        return null;
    }

}

测试：

java 复制代码

public class Main {
    public static void main(String[] args) {
        ZuDao zuDao = new ZuDao();
        Waiters waiter = zuDao.getWaiter(1);
        waiter.service();

        Waiters waiter1 = zuDao.getWaiter(2);
        waiter1.service();

        Waiters waiter2 = zuDao.getWaiter(1);
        System.out.println(waiter2);

        waiter.end();
        waiter1.end();
    }
}