public class Account
{
   // 顯式定義Lock對(duì)象
   private final Lock lock = new ReentrantLock();
   // 獲得指定Lock對(duì)象對(duì)應(yīng)的Condition
   private final Condition cond = lock.newCondition();
   // 封裝賬戶編號(hào)、賬戶余額的兩個(gè)成員變量
   private String accountNo;
   private double balance;
   // 標(biāo)識(shí)賬戶中是否已有存款的旗標(biāo)
   private boolean flag = false;
   public Account(){}
   // 構(gòu)造器
   public Account(String accountNo , double balance)
   {
      this.accountNo = accountNo;
      this.balance = balance;
   }
   // accountNo的setter和getter方法
   public void setAccountNo(String accountNo)
   {
      this.accountNo = accountNo;
   }
   public String getAccountNo()
   {
      return this.accountNo;
   }
   // 因此賬戶余額不允許隨便修改，所以只為balance提供getter方法，
   public double getBalance()
   {
      return this.balance;
   }
   public void draw(double drawAmount)
   {
      // 加鎖
      lock.lock();
      try
      {
        // 如果flag為假，表明賬戶中還沒有人存錢進(jìn)去，取錢方法阻塞
        if (!flag)
        {
           cond.await();
        }
        else
        {
           // 執(zhí)行取錢
           System.out.println(Thread.currentThread().getName()
              + " 取錢:" + drawAmount);
           balance -= drawAmount;
           System.out.println("賬戶余額為：" + balance);
           // 將標(biāo)識(shí)賬戶是否已有存款的旗標(biāo)設(shè)為false。
           flag = false;
           // 喚醒其他線程
           cond.signalAll();
        }
      }
      catch (InterruptedException ex)
      {
        ex.printStackTrace();
      }
      // 使用finally塊來釋放鎖
      finally
      {
        lock.unlock();
      }
   }
   public void deposit(double depositAmount)
   {
      lock.lock();
      try
      {
        // 如果flag為真，表明賬戶中已有人存錢進(jìn)去，則存錢方法阻塞
        if (flag)       // ①
        {
           cond.await();
        }
        else
        {
           // 執(zhí)行存款
           System.out.println(Thread.currentThread().getName()
              + " 存款:" + depositAmount);
           balance += depositAmount;
           System.out.println("賬戶余額為：" + balance);
           // 將表示賬戶是否已有存款的旗標(biāo)設(shè)為true
           flag = true;
           // 喚醒其他線程
           cond.signalAll();
        }
      }
      catch (InterruptedException ex)
      {
        ex.printStackTrace();
      }
      // 使用finally塊來釋放鎖
      finally
      {
        lock.unlock();
      }
   }
   // 下面兩個(gè)方法根據(jù)accountNo來重寫hashCode()和equals()方法
   public int hashCode()
   {
      return accountNo.hashCode();
   }
   public boolean equals(Object obj)
   {
      if(this == obj)
        return true;
      if (obj !=null
        && obj.getClass() == Account.class)
      {
        Account target = (Account)obj;
        return target.getAccountNo().equals(accountNo);
      }
      return false;
   }
}

public class DrawThread extends Thread
{
   // 模擬用戶賬戶
   private Account account;
   // 當(dāng)前取錢線程所希望取的錢數(shù)
   private double drawAmount;
   public DrawThread(String name , Account account
      , double drawAmount)
   {
      super(name);
      this.account = account;
      this.drawAmount = drawAmount;
   }
   // 重復(fù)100次執(zhí)行取錢操作
   public void run()
   {
      for (int i = 0 ; i < 100 ; i++ )
      {
        account.draw(drawAmount);
      }
   }
}

public class DepositThread extends Thread
{
   // 模擬用戶賬戶
   private Account account;
   // 當(dāng)前取錢線程所希望存款的錢數(shù)
   private double depositAmount;
   public DepositThread(String name , Account account
      , double depositAmount)
   {
      super(name);
      this.account = account;
      this.depositAmount = depositAmount;
   }
   // 重復(fù)100次執(zhí)行存款操作
   public void run()
   {
      for (int i = 0 ; i < 100 ; i++ )
      {
        account.deposit(depositAmount);
      }
   }
}

public class DrawTest
{
   public static void main(String[] args)
   {
      // 創(chuàng)建一個(gè)賬戶
      Account acct = new Account("1234567" , 0);
      new DrawThread("取錢者" , acct , 800).start();
      new DepositThread("存款者甲" , acct , 800).start();
      new DepositThread("存款者乙" , acct , 800).start();
      new DepositThread("存款者丙" , acct , 800).start();
   }
}