public class DeadLock {

    private static Integer accountA = 1000; // 账户A，有1000元

    private static Integer accountB = 2000; // 账户B，有2000元

    public static void main(String[] args) throws Exception {
        // 模拟A转账500元给B的过程
        Thread a2b = new Thread(new Runnable() {
            public void run() {
                synchronized (accountA) { // 先拿出A的存折
                    System.out.println("Check A's account.");
                    try {
                        Thread.sleep(200); // 假设这句话负责检查下A够不够钱 
                    } catch (InterruptedException e) {
                    }
                    System.out.println("A got " + accountA + ", try to start transfer.");
                    synchronized (accountB) { // 去拿B的存折（其实这里就是死锁发生的位置了）
                        // 从A存折取出500
                        accountA = accountA - 500;
                        // 存入B存折
                        accountB = accountB + 500;
                        System.out.println("Transfer A2B done, now A: " + accountA + ", B: " + accountB);
                    }
                }
            }
        });

        // 模拟B转账500元给A的过程
        Thread b2a = new Thread(new Runnable() {
            public void run() {
                synchronized (accountB) { // 先拿出B的存折
                    System.out.println("Check B's account.");
                    try {
                        Thread.sleep(200); // 假设这句话负责检查下B够不够钱 
                    } catch (InterruptedException e) {
                    }
                    System.out.println("B got " + accountB + ", try to start transfer.");
                    synchronized (accountA) { // 去拿A的存折（其实这里就是死锁发生的位置了）
                        // 从B存折取出500
                        accountB = accountB - 500;
                        // 存入A存折
                        accountA = accountA + 500;
                        System.out.println("Transfer B2A done, now A: " + accountA + ", B: " + accountB);
                    }
                }
            }
        });

        // 这两笔转账要求同时发生了
        a2b.start();
        b2a.start();

        // join 只是负责等待这两笔转账业务的线程结束而已
        a2b.join();
        b2a.join();
    }
}