import java.util.concurrent.locks.ReentrantLock;

public class Account
{
 /**
  * 同步锁
  */
 private final ReentrantLock lock = new ReentrantLock();

 /**
  * 账户号
  */
 private String accountNo;
 /**
  * 账户余额
  */
 private double balance;

 public Account()
 {
  super();
 }

 public Account(String accountNo, double balance)
 {
  super();
  this.accountNo = accountNo;
  this.balance = balance;
 }

 @Override
 public int hashCode()
 {
  return accountNo.hashCode();
 }

 @Override
 public boolean equals(Object obj)
 {
  if (null != obj && obj.getClass() == Account.class)
  {
   Account target = (Account) obj;
   return target.accountNo.equals(accountNo);
  }
  return false;
 }

 /**
  * 同步方法，同步方法的监视器是this，同步方法可以将该类变为线程安全的类
  * 任何时候只有一个线程获得对Account对象的锁定，然后进入draw方法进行取钱
  */
 public void draw(double drawAmount)
 {
  lock.lock();
  try
  {
   if (balance >= drawAmount)
   {
    System.out.println(Thread.currentThread().getName()

          + "取出钞票成功" + drawAmount);
    balance -= drawAmount;
    System.out.println("余额为" + balance);
   }
   else
   {
    System.out.println("余额不足");
   }
  }
  finally
  {
   // 用finally块保证释放锁
   lock.unlock();
  }
 }

 /* 只提供Getters，不提供Setters，确保安全*/

 public String getAccountNo()
 {
  return accountNo;
 }

 public double getBalance()
 {
  return balance;
 }
}

public class DrawThread extends Thread
{
 /**
  * 模拟账户
  */
 private Account ac;

 /**
  * 当前取钱线程希望取得的钱数
  */
 private double drawAmount;

 public DrawThread(String name, Account ac, double drawAmount)
 {
  super(name);
  this.ac = ac;
  this.drawAmount = drawAmount;
 }

 @Override
 public void run()
 {
  ac.draw(drawAmount);
 }
}
 

public class Test
{
 public static void main(String[] args)
 {
  Account ac = new Account("00000001", 1000);
  Thread t1 = new Thread(new DrawThread("Lily", ac, 800));
  Thread t2 = new Thread(new DrawThread("Tom", ac, 800));
  t1.start();
  t2.start();
 }
}

本文转自IT徐胖子的专栏博客51CTO博客，原文链接http://blog.51cto.com/woshixy/1058853如需转载请自行联系原作者

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