Condition控制线程通信
Condition可以用来控制线程间的通信,与wait、notify和notifyAll
方法对应的分别是await、signal和sinalAll
上篇文章中的生产者消费者采用的是 synchronized
和对象的wait
和notifyAll
方法,可以采用Lock锁
结合condition
来代替,具体代码如下:
依然是修改Clerk类
class Clerk{
private int product = 0;
private Lock lock = new ReentrantLock();
private Condition condition = lock.newCondition();
//进货方法
public void get()
{
lock.lock();
try {
while (product>=10){
System.out.println("产品已满!无法添加");
try {
condition.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName()+":"
+ ++product);
condition.signalAll();
}
finally {
lock.unlock();
}
}
//卖货方法
public void sale()
{
lock.lock();
try {
while (product<=0)
{
System.out.println("缺货!");
try {
condition.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName()+":"+
--product);
condition.signalAll();
}
finally {
lock.unlock();
}
}
}
代码逻辑:
- 首先用Lock对象代替
synchronized
的作用 - 采用
condition
对象的await
、signalAll
方法让线程等待和唤醒
实际执行结果:
可以达到同样的效果
线程按序交替案例
要求:开启三个线程A、B、C,每个线程分别负责打印A、B、C,要求按序打印20次
即 ABCABCABC…
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class Main {
public static void main(String[] args)
{
AlternateDemo alternateDemo = new AlternateDemo();
new Thread(new Runnable() {
@Override
public void run() {
for (int i=1;i<=20;i++)
{
alternateDemo.loopA(i);
}
}
},"A").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i=1;i<=20;i++)
{
alternateDemo.loopB(i);
}
}
},"B").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i=1;i<=20;i++)
{
alternateDemo.loopC(i);
System.out.println("_____________");
}
}
},"C").start();
}
}
class AlternateDemo{
private int number = 1; //当前正在执行线程的标记
private Lock lock= new ReentrantLock() ;
private Condition condition1 = lock.newCondition();
private Condition condition2 = lock.newCondition();
private Condition condition3 = lock.newCondition();
/**
*
* @param totalLoop
*/
public void loopA(int totalLoop){
lock.lock();
try {
//1.判断当前标志位是否为1
if(number != 1)
{
condition1.await();
}
System.out.println(Thread.currentThread().getName()+"\t" +
"\t"+ totalLoop);
//2.A打印完毕,唤醒其他线程
number = 2;
condition2.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopB(int totalLoop){
lock.lock();
try {
//1.判断当前标志位是否为2
if(number != 2)
{
condition2.await();
}
System.out.println(Thread.currentThread().getName()+"\t" +
"\t"+ totalLoop);
//2.B打印完毕,唤醒其他线程
number = 3;
condition3.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopC(int totalLoop){
lock.lock();
try {
//1.判断当前标志位是否为3
if(number != 3)
{
condition3.await();
}
System.out.println(Thread.currentThread().getName()+"\t" +
"\t"+ totalLoop);
//2.C打印完毕,唤醒其他线程
number = 1;
condition1.signal();
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}