/**
 * Created by gmy on 2017/10/14.
 */
public class App {
    public static void main(String[] args) throws InterruptedException {
        final Runner runner=new Runner();
        Thread t1=new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    runner.firstThread();
                } catch
 
 (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        Thread t2 =new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    runner.secondThread();
                }catch
 
 (InterruptedException ignored){

                }
            }
        });
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        runner.finished();
    }
}

/**
 * Created by gmy on 2017/10/14.
 */
public class Runner {
    private Account account1=new Account();
    private
 
 Account account2=new Account();
    private Lock lock1=new ReentrantLock();
    private Lock lock2=new ReentrantLock();

    private void acquireLocks(Lock firstLock,Lock secondLock) throws InterruptedException{
        while(true){
            boolean gotFirstLock=false;
            boolean gotSecondLock=false;
            try {
                gotFirstLock=firstLock.tryLock();//tryLock是看這個鎖是否是可用的，沒有被其他執行緒佔用
                gotSecondLock=secondLock.tryLock();
            }finally {
                if(gotFirstLock&&gotSecondLock)return;
                else if (gotFirstLock)firstLock.unlock();
                else if (gotSecondLock)secondLock.unlock();
            }
            Thread.sleep(1);
        }
    }
    public void firstThread()throws InterruptedException{
        Random random=new Random();
        for (int i=0;i<10000;i++){
            acquireLocks(lock1,lock2);
            try {
                Account.transfer(account1,account2,random.nextInt(100));
            }finally {
                lock1.unlock();
                lock2.unlock();
            }
        }
    }
    public void secondThread()throws InterruptedException{
        Random random=new Random();
        for (int i=0;i<10000;i++){
            acquireLocks(lock2,lock1);
            try {
                Account.transfer(account2,account1,random.nextInt(100));
            }finally {
                lock1.unlock();
                lock2.unlock();
            }
        }
    }
    public void finished(){
        System.out.println("Account 1 balance "+account1.getBalance());
        System.out.println("Account 2 balance "+account2.getBalance());
        System.out.println("Total balance"+(account2.getBalance()+account1.getBalance()));
    }

}

public class Account {
    private int balance=10000;//底金
    public void deposit(int amount){//存錢
        balance+=amount;
    }
    public void withdraw(int amount){//取錢
        balance-=amount;
    }
    public int getBalance(){
        return balance;
    }
    public static void transfer(Account account1,Account account2,int amount){//轉賬
        account1.withdraw(amount);
        account2.deposit(amount);
    }
}

解析:

1. thread.Join把指定的執行緒加入到當前執行緒。例如在main 執行緒中呼叫了t1.join()是指t1執行緒執行完畢