java线程协作

协作方式

基于对象的内置锁,在同步方法或同步块中使用wait(),notify(),notifyAll()

Lock配合Condition对象的await(),signal(),signalAll()

下面的例子模拟多线程环境下的存款取款业务

1.第一种方式实现

public class JavaInnerLock {

private int balance = 0;

public synchronized void save(int x) {
balance += x;
System.out.println("存入" + x + "元,现有余额" + balance + "元");
notify();

}

public synchronized void draw(int x) throws InterruptedException {
while (balance < x) {
System.out.println("欲取" + x + "元," + "余额不足");
wait();
}
balance -= x;
System.out.println("取出" + x + "元,现有余额" + balance + "元");
}

public void test() {
for (int i = 0; i < 5; i++) {
new Drawer(this).start();
new Saver(this).start();

}
}

}

class Saver extends Thread {
private JavaInnerLock account;

public Saver(JavaInnerLock account) {
this.account = account;
}

public void run() {
int money = (int) (Math.random() * 100);
account.save(money);
}
}

class Drawer extends Thread {
private JavaInnerLock account;

public Drawer(JavaInnerLock account) {
this.account = account;
}

public void run() {
int money = (int) (Math.random() * 100);
try {
account.draw(money);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

2.第二种方式实现

package test;

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

public class JavaCondition {

private int balance = 0;
private Lock lock = new ReentrantLock();
private Condition draw = lock.newCondition();

public void save(int x) {
lock.lock();
try {
balance += x;
System.out.println("存入" + x + "元,现有余额" + balance + "元");
draw.signal();
} finally {
lock.unlock();
}

}

public void draw(int x) throws InterruptedException {
lock.lock();
try {
while (balance < x) {
System.out.println("欲取" + x + "元," + "余额不足");
draw.await();
}
balance -= x;
System.out.println("取出" + x + "元,现有余额" + balance + "元");
} finally {
lock.unlock();
}
}

public void test() {
for (int i = 0; i < 5; i++) {
new Drawer(this).start();
new Saver(this).start();

}
}

}

class Saver extends Thread {
private JavaCondition account;

public Saver(JavaCondition account) {
this.account = account;
}

public void run() {
int money = (int) (Math.random() * 100);
account.save(money);
}
}

class Drawer extends Thread {
private JavaCondition account;

public Drawer(JavaCondition account) {
this.account = account;
}

public void run() {
int money = (int) (Math.random() * 100);
try {
account.draw(money);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

3测试结果

欲取94元,余额不足

欲取24元,余额不足

欲取78元,余额不足

欲取24元,余额不足

存入89元,现有余额89元

欲取94元,余额不足

存入65元,现有余额154元

存入18元,现有余额172元

取出78元,现有余额94元

存入73元,现有余额167元

存入42元,现有余额209元

取出24元,现有余额185元

取出94元,现有余额91元

取出24元,现有余额67元

取出23元,现有余额44元