Java code
import java.io.*;
class Account
{
private String name;
private double balance;
public Account(String name)
{
this.name=name;
balance=0;
}
public String getName()
{
return name;
}
public double getBalance()
{
return balance;
}
public void put(double value)
{
if(value>0)
balance=balance+value;
}
public double get(double value)
{
if(value>0)
{
if(value<=this.balance)
this.balance-=value;
else
{
value=this.balance;
this.balance=0;
}
return value;
}
else
return 0;
}
}
class Save extends Thread
{
private double val;
private Account account;
public Save(Account a1,double val)
{
this.account=a1;
this.val=val;
}
public void run()
{
double howmuch;
howmuch=this.account.getBalance();
this.account.put(val);
try
{
sleep(1);
}
catch(InterruptedException e) { }
System.out.println(this.account.getName()+"账户：现有"+howmuch+"，存入："+this.val+"，余额："+this.account.getBalance());
}
}
class Fetch extends Thread
{
private double val;
private Account account;
public Fetch(Account a1,double val)
{
this.account=a1;
this.val=val;
}
public void run()
{
double howmuch=this.account.getBalance();
try
{
sleep(1);
}
catch(InterruptedException e){}
System.out.println(this.account.getName()+"账户：现有"+howmuch+"，取出："+this.account.get(val)+"，余额："+this.account.getBalance());
}
}
public class App2_1 {
public static void main(String args[])
{
Account wang=new Account("wang");
(new Save(wang,100)).start();
(new Save(wang,200)).start();
(new Fetch(wang,300)).start();
}
}
有一次运行结果如下：
wang账户：现有300.0，取出：300.0，余额：0.0
wang账户：现有0.0，存入：100.0，余额：0.0
wang账户：现有100.0，存入：200.0，余额：300.0
怎么想也想不出这3个线程是按什么顺序推进的，尤其是最后一行的余额为什么是300，不应该是0吗？
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