线程 不安全的代码案例，为什么就不安全了

线程同步

队列加锁synchronized是实现同步的必要条件。
优先级低的拿到锁，高的没拿到。性能倒置，效率极差

不安全的买票代码实现

//模拟不安全的买票情况
public class SynchronizeTest {
    //线程不安全
    public static void main(String[] args) {//启动三个线程操纵一份票
        BuyTicker buyTicker = new BuyTicker();
        new Thread(buyTicker,"我").start();
        new Thread(buyTicker,"你").start();
        new Thread(buyTicker,"黄牛").start();
    }
}
class BuyTicker implements Runnable{
    private int ticketNum = 10;
    boolean flag = true; //利用标志位结束run()方法
    @Override
    public void run() {
        while(flag){//外部停止方式
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    public void buy() throws InterruptedException {//sleep()要抛出中断异常
        //判断是否有票
        if(ticketNum<=0){
            System.out.println("票卖完了");
            flag = false;
            return;
        }
        Thread.sleep(1000);//延时是为了看出效果，不然cpu运算太快了
        System.out.println(Thread.currentThread().getName()+"拿到"+ticketNum--);
    }
}

不安全银行代码

public class UnsafeBake {
    public static void main(String[] args) {
        Account account = new Account("结婚基金",100);
        Draw you = new Draw(account,50,"你");
        Draw girlFriend = new Draw(account,100,"女朋友");
        you.start();
        girlFriend.start();
    }
}
class Account{//账户类，初始化一个账户
    String name;
    int money;
    public Account(String name, int money) {
        this.name = name;
        this.money = money;
    }
}
class Draw extends Thread{//取钱类
    Account account;//需要账户，
    int drawMoney;//取款金额
    int noMoney;//账户余额
    public Draw(Account account, int drawMoney, String name) {
        super(name);//初始化谁，取了多少钱
        this.account = account;
        this.drawMoney = drawMoney;
    }
    @Override
    public void run() {
        if(account.money-drawMoney<0){//取钱判断
            System.out.println("余额不足");
            return;
        }
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        account.money = account.money - drawMoney;
        noMoney = noMoney +drawMoney;
        System.out.println(account.name+"余额为："+account.money);//取完钱提示你取出多少，余额多少
        System.out.println(this.getName()+"手里的钱"+noMoney);//继承THread可以直接写this
    }
}

不安全的列表

import java.util.ArrayList;
import java.util.List;
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();
        }
        System.out.println(list.size());
    }
}