必然死锁——模拟两个人转账

使用syn锁对from和to进行资源的加锁。如果转账者和被转账的人都获取了相应的锁而不释放，则会造成必然的死锁。

package deadlock;

/**
 * @author leon
 * @描述  转账时候遇到死锁，一旦打开注释。便会发生死锁。
 */
public class TransferMoney  implements Runnable{

    int flag  = 1;
    static Account a = new Account(500);
    static Account b = new Account(500);

    public static void main(String[] args) throws InterruptedException {
        TransferMoney r1 = new TransferMoney();
        TransferMoney r2 = new TransferMoney();
        r1.flag = 1;
        r2.flag = 0;
        Thread t1 = new Thread(r1);
        Thread t2 = new Thread(r2);
        t1.start();
        t2.start();
        t1.join();







        t2.join();
        System.out.println("a的余额" + a.balance + "元");
        System.out.println("b的余额" + b.balance + "元");

    }
    @Override
    public void run() {
        if (flag == 1) {
            transferMoney(a, b, 200);
        }
        if (flag == 0) {
            transferMoney(b, a, 200);
        }
    }
    public static void transferMoney(Account from, Account to, int amount) {
        synchronized (from) {
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (to) {
                if (from.balance - amount < 0) {
                    System.out.println("余额不足，转账失败");
                }
                from.balance -= amount;
                to.balance += amount;
                System.out.println("转账成功，" + amount +"元");
            }
        }
    }
    static  class Account {
        public Account(int balance) {
            this.balance = balance;
        }

        int balance;

    }
}

 

 

 

通过使用jps和jstack命令查到：