先写三个例子来看一下：
第一个线程不安全的例子：买票
//不安全的买票 public class TestSyn { public static void main(String[] args) { BuyTicket station = new BuyTicket(); new Thread(station, "我").start(); new Thread(station, "你们").start(); new Thread(station, "黄牛党").start(); } } class BuyTicket implements Runnable { //票 private int ticketNum = 10; //循环标志 boolean flag = true; @Override public void run() { //买票 while (flag) { try { buyTicket(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void buyTicket() throws InterruptedException { //判断是否有票 if (ticketNum <= 0) { flag = false; return; } //模拟延时 Thread.sleep(100); //买票 System.out.println(Thread.currentThread().getName() + "拿到" + ticketNum--); } } 在这里插入代码片有人同时拿到第一张票，这种是不可能的，是线程不同步的
第二个线程不安全的例子：取钱
package duoxiancheng; public class TestBank { 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, 60, "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 int drawingMoney; //取了多少钱 int nonMoney; //现在手里有多少钱 public Drawing(Account account, int drawingMoney, String name) { super(name); this.account = account; this.drawingMoney = drawingMoney; } @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 - 取出的钱 account.money = account.money - drawingMoney; //手里的钱 nonMoney = nonMoney + drawingMoney; System.out.println(account.name + "余额为：" + account.money); System.out.println(this.getName() + "手里的钱" + nonMoney); } }线程不安全时候会输出钱数为负数 第三个线程不安全的例子：集合
package duoxiancheng; 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()); } }这个也是不安全的例子
好了，今天先到这里了~
