java线程学习4——线程同步之同步代码块-优快云博客

本文通过一个简单的Java程序模拟了两个线程同时从同一银行账户中取款的过程，并使用synchronized关键字确保了账户余额的更新是线程安全的。

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模拟一个场景，两个人对同一个账户同时取钱

package cn.xy.Thread;

public class Account
{
/**
* 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;
}

/***************************************************************************/

public String getAccountNo()
{
return accountNo;
}

public void setAccountNo(String accountNo)
{
this.accountNo = accountNo;
}

public double getBalance()
{
return balance;
}

public void setBalance(double balance)
{
this.balance = balance;
}
}

package cn.xy.Thread;

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()
{
// 同时需要操作的账户作为同步监视器,synchronized{}中的代码被称为同步代码块
synchronized (ac)
{
if (ac.getBalance() >= drawAmount)
{
System.out.println(getName() + "取出钞票成功" + drawAmount);
ac.setBalance(ac.getBalance() - drawAmount);
System.out.println("余额为" + ac.getBalance());
}
else
{
System.out.println("余额不足");
}
}
}
}

package cn.xy.Thread;

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();
}
}