Java线程同步Lock同步锁代码示例

package lock.reentrantlock2;
import java.util.concurrent.locks.*;
/**
 *账户类，需保持同步
 */
public class Account
{
  //定义锁对象
  private final ReentrantLock lock = new ReentrantLock();
  private String accountNo;
  private double balance;
  public Account(){}
  public Account(String accountNo , double balance)
  {
    this.accountNo = accountNo;
    this.balance = balance;
  }
  public void setAccountNo(String accountNo)
  {
    this.accountNo = accountNo;
  }
  public String getAccountNo()
  {
     return this.accountNo;
  }
  public double getBalance()
  {
     return this.balance;
  }
  public void draw(double drawAmount)
  {
    lock.lock();
    try
    {
      //账户余额大于取钱数目
      if (balance >= drawAmount)
      {
        //吐出钞票
        System.out.println(Thread.currentThread().getName() +
          "取钱成功！吐出钞票:" + drawAmount);
        try
        {
          Thread.sleep(1);      
        }
        catch (InterruptedException ex)
        {
          ex.printStackTrace();
        }
        //修改余额
        balance -= drawAmount;
        System.out.println("\t余额为: " + balance);
      }
      else
      {
        System.out.println(Thread.currentThread().getName() +
          "取钱失败！余额不足！");
      }     
    }
    finally
    {
      lock.unlock();
    }
  }
  public int hashCode()
  {
    return accountNo.hashCode();
  }
  public boolean equals(Object obj)
  {
    if (obj != null && obj.getClass() == Account.class)
    {
      Account target = (Account)obj;
      return target.getAccountNo().equals(accountNo);
    }
    return false;
  }
}

package lock.reentrantlock2;
/**
 * 调用account取钱
 *
 */
public class DrawThread extends Thread
{
  //模拟用户账户
  private Account account;
  //当前取钱线程所希望取的钱数
  private double drawAmount;
  public DrawThread(String name , Account account ,
    double drawAmount)
  {
    super(name);
    this.account = account;
    this.drawAmount = drawAmount;
  }
  //当多条线程修改同一个共享数据时，将涉及到数据安全问题。
  public void run()
  {
    account.draw(drawAmount);
  }
}

package lock.reentrantlock2;
/**
 */
public class TestDraw
{
  public static void main(String[] args)
  {
    //创建一个账户
    Account acct = new Account("1234567" , 1000);
    //模拟两个线程对同一个账户取钱
    new DrawThread("甲" , acct , 800).start();
    new DrawThread("乙" , acct , 800).start();
  }
}