java线程学习5——线程同步之同步方法-优快云博客

本文通过一个Java账户类实例展示了如何使用同步方法实现线程安全的资金取款操作。两个线程尝试从同一个账户中取出相同金额，通过`synchronized`关键字确保了操作的原子性和线程安全性。

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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;
}

/**
* 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 synchronized void draw(double drawAmount)
{
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");
}
}

/********************** 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();
}
}