java多线程-Atomic

Atomic原子包简单使用，此处用AtomicInteger来进行计数（其他的都差不多）

import java.util.concurrent.atomic.AtomicInteger;public class Ticket {    public final  AtomicInteger x = new AtomicInteger(1000000);}

以买票为例，此处为票的数量，一个简单的类，接着调用线程来去买票。

class BuyTicket implements Runnable {    private Ticket ticket;    public BuyTicket(Ticket ticket) {        this.ticket = ticket;    }    @Override    public void run() {           ticket.x.getAndAdd(-1);    }}

调用10000个线程去买票

public class BuyTicketThreadDemo {    public static void main(String args[]) throws InterruptedException {        Ticket ticket = new Ticket();        System.out.printf("\n票的余数 = %d\n", ticket.x.get());        Runnable r1 = new BuyTicket(ticket);        Thread []thread = new Thread[10000];        for (int i = 0; i < 10000; i++) {            thread[i] = new Thread(r1);        }        for (int i = 0; i < 10000; i++) {            thread[i].start();         }        Thread.sleep(500);        System.out.println("\b\nThe remainder of the ticket is " + ticket.x.get());    }}

结果为990000，这是正确的。
具体的可以从这里看，写的很好，我就不重复说了java-多线程深入（五）Atomic
Java的Actomic类分析

---

现在考虑一种情况，如果我想买票之前判断票是否有剩余怎么办

class BuyTicket implements Runnable {    private Ticket ticket;    public BuyTicket(Ticket ticket) {        this.ticket = ticket;    }    @Override    public void run() {   //同步             if (ticket.x.addAndGet(-1) < 0) {            System.out.println("购买失败!");            ticket.x.getAndIncrement();        } else {            System.out.println("购买成功!");        }    }}

就相当于买的时候，先虚晃一下，看看买完是不是符合条件，如果不符合，就还回去。