线程三大不安全案例

线程三大不安全案例

• 买票

//不安全的买票
//线程不安全，有负数
public class UnsafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();


        new Thread(station,"苦逼的我").start();
        new Thread(station,"牛逼的你们").start();
        new Thread(station,"可恶的黄牛党").start();
    }

}

class BuyTicket implements Runnable{

    //票
    private int ticketNums = 10;
    boolean flag = true; //外部停止方式

    @Override
    public void run() {
        //买票
        while (flag){
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private void buy() throws InterruptedException {
        //判断是否有票
        if(ticketNums<=0){
            flag = false;
            return;
        }
        //模拟延时
        Thread.sleep(100);

        //买票
        System.out.println(Thread.currentThread().getName()+"拿到"+ticketNums--);
    }
}

• 银行取钱

//不安全的取钱
//两个人去银行取钱，账户
public class UnsafeBank {
    public static void main(String[] args) {
        //账户
        Account account = new Account(100,"结婚基金");

        Drawing you = new Drawing(account,50,"你");
        Drawing girlFriend = new Drawing(account,50,"girlFriend");

        you.start();
        girlFriend.start();
    }
}

//账户
class Account{
    int money; //余额
    String name; //卡名

    public Account(int money, String name) {
        this.money = money;
        this.name = name;
    }
}

//银行：模拟取款
class Drawing extends Thread{

    Account account; //账户
    //取了多少钱
    int drawingMoney;
    //现在手里有多少钱
    int nowMoney;

    public Drawing(Account account,int drawingMoney,String name){
        super(name);
        this.account = account;
        this.drawingMoney = drawingMoney;


    }

    //取钱

    @Override
    public void run() {
        //判断有没有钱
        if (account.money-drawingMoney<0){
            System.out.println(Thread.currentThread().getName()+"钱不够，取不了");
            return;
        }

        //sleep可以放大问题的发生性
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //卡内余额 = 余额 - 你取的钱
        account.money = account.money - drawingMoney;
        //你手里的钱
        nowMoney = nowMoney + drawingMoney;

        System.out.println(account.name+"余额为:"+account.money);
        //getName()+Thread.currentThread().getName() = this.getName()
        System.out.println(this.getName()+"手里的钱："+nowMoney);
    }
}

• 线程不安全的集合

import java.util.ArrayList;
import java.util.List;

//线程不安全的集合
public class UnsafeList {
    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
        for (int i = 0; i < 10000; i++) {
            new Thread(()->{
                list.add(Thread.currentThread().getName());
            }).start();
        }
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}