死锁检查和查看

用户A转账给用户B，用户B转账给用户A

public class Account {
    private Integer balance = 200;

    private void transfer(Account target, int amount){
        synchronized (this){
            synchronized (target){
                if(this.balance >= amount){
                    this.balance -= amount;
                    target.balance += amount;
                }
            }
        }
    }

    public static void main(String[] args){

        for(int i = 0 ; i < 100000 ; i++ ) {
            Account account1 = new Account();
            Account account2 = new Account();
            Account account3 = new Account();
            Account account4 = new Account();

            Thread th1 = new Thread(() -> {
                account1.transfer(account2, 100);
            });
            Thread th2 = new Thread(() -> {
                account2.transfer(account1, 100);
            });

            th1.start();
            th2.start();
            try {
                th1.join();
                th2.join();
            } catch (Exception e) {
                System.out.println(e);
            }
            System.out.println(i);

        }

    }
}

重复试验直到有死锁现象出现，运用jconsole工具查看死锁

本地进程 -> 连接

线程 -> 检查死锁 ：两个线程分别占有对方所需要的锁，形成死锁