java多线程问题中简单的存取款实现

package com.mnmlist.java.grammar;

import java.util.Random;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

class Customer {
int total;
public Customer() {
total = 0;
}

public final ReentrantLock lock = new ReentrantLock();// 问题1：lock为什么定义为final
Random random = new Random();
public void put(int num) {

System.out.println(Thread.currentThread().getName()+":before put "+num+" ,total:" + total);
total += num;
System.out.println(Thread.currentThread().getName()+":after put:" + num + ",total:" + total);

}

public void get(int num) {
System.out.println(Thread.currentThread().getName()+":before get "+num+" ,the total is:" + total);
total -= num;
System.out.println(Thread.currentThread().getName()+":after get " + num + " ,the total is:" + total);
}
}

class PutMoney implements Runnable {
Customer customer;

public PutMoney(Customer customer) {
this.customer = customer;
}

public void run() {
int num = 0;
while (true) {
num = customer.random.nextInt(100);
if (num < 0)
num = -num;
customer.lock.lock();
if (customer.total + num <0) {
customer.lock.unlock();
try {
Thread.sleep(100);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
customer.put(num);
customer.lock.unlock();
}
}
}

}

class GetMoney implements Runnable {
Customer customer;

public GetMoney(Customer customer) {
this.customer = customer;
}

public void run() {
int num = 0;
while (true) {
num = customer.random.nextInt(100);
if (num < 0)
num = -num;
customer.lock.lock();
if (customer.total - num < 0) {
customer.lock.unlock();
try {
Thread.sleep(100);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
customer.get(num);
customer.lock.unlock();
}
}
}
}

public class BankTheadDemo {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Customer customer = new Customer();
PutMoney putMoney = new PutMoney(customer);
GetMoney getMoney = new GetMoney(customer);
Thread t1 = new Thread(putMoney);
Thread t2 = new Thread(getMoney);
t2.start();
t1.start();

}

}