java多线程同步示例，来自《疯狂java讲义》。通过synchronized，wait()，notify(),notifyAll()实现多线程同步与通信。假设现在系统中有两个线程，这两个线程分别代表存钱者和取钱者---现在假设系统有一种特殊的要求，系统要求存款者和取钱者不断地重复存钱、取钱动作，而且要求每当存款着将钱存入指定账户后，取钱者就立即取出这笔钱。不允许存款者连续两次存钱，也不允许取钱者连续两次取钱。程序中，通过一个旗标flag标识，本次账户操作是不是存款操作，以便下次操作可以探测。可类比:http://www.oschina.net/code/snippet_820500_44795

1.[代码]Account账户类，有取钱(drawBalance)和存钱(deposit)两个同步方法

package com.sunchp;

public class Account {

private String accountNo;

private double balance;

private boolean flag = false;

public Account(String _accountNo, double _balance) {

this.accountNo = _accountNo;

this.balance = _balance;

}

public String getAccountNo() {

return accountNo;

}

public void setAccountNo(String accountNo) {

this.accountNo = accountNo;

}

public double getBalance() {

return balance;

}

public synchronized void drawBalance(double drawBalance) {

if (flag) {

if (balance > drawBalance) {

System.out.println(Thread.currentThread().getName() + "取钱成功，正在吐钞：" + drawBalance);

balance -= drawBalance;

flag = false;

this.notifyAll();

System.out.println(Thread.currentThread().getName() + "余额为：" + getBalance());

} else {

System.out.println(Thread.currentThread().getName() + "取钱失败，余额不足");

}

} else {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

public synchronized void deposit(double depositBalance) {

if (flag) {

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

} else {

System.out.println(Thread.currentThread().getName() + " 存款：" + depositBalance);

this.balance += depositBalance;

flag = true;

this.notifyAll();

System.out.println(Thread.currentThread().getName() + "余额为：" + getBalance());

}

}

}

2.[代码]取钱线程类

package com.sunchp;

public class MyThread1 implements Runnable {

private Account account;

private double drawBalance;

public Account getAccount() {

return account;

}

public void setAccount(Account account) {

this.account = account;

}

public double getDrawBalance() {

return drawBalance;

}

public void setDrawBalance(double drawBalance) {

this.drawBalance = drawBalance;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

account.drawBalance(drawBalance);

}

}

}

3.[代码]存钱线程类

package com.sunchp;

public class MyThread2 implements Runnable {

private Account account;

private double depositBalance;

public Account getAccount() {

return account;

}

public void setAccount(Account account) {

this.account = account;

}

public double getDepositBalance() {

return depositBalance;

}

public void setDepositBalance(double depositBalance) {

this.depositBalance = depositBalance;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

account.deposit(depositBalance);

}

}

}

4.[代码]测试类，main方法

package com.sunchp;

public class Test {

public static void main(String[] args) throws Exception {

Account acc = new Account("001", 1000);

MyThread1 mt1 = new MyThread1();

mt1.setAccount(acc);

mt1.setDrawBalance(20);

Thread t1 = new Thread(mt1, "取钱者1");

Thread t2 = new Thread(mt1, "取钱者2");

MyThread2 mt2 = new MyThread2();

mt2.setAccount(acc);

mt2.setDepositBalance(20);

Thread t3 = new Thread(mt2, "存钱者1");

Thread t4 = new Thread(mt2, "存钱者2");

t1.start();

t2.start();

t3.start();

t4.start();

}

}