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本篇讲的是lock.condition()的正确使用方式(也是之前看过的一篇，今天又把他实现出来)
首先，代码逻辑规则如下:
1.使用3个线程依次打印ABC
直接上代码:
package Thread;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
*
* @ClassName: LockConditionTest
* @Description:三个线程依次打印ABC
* @author:
* @date: 2019年6月27日 下午4:31:41
* @version 1.8.0
* @param
*
*/
public class LockConditionTest{
public static void main(String[] args) {
final AlternateDemo ad = new AlternateDemo();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopA();
}
}
}, "A").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopB();
}
}
}, "B").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopC();
System.out.println("-----------------------------------");
}
}
}, "C").start();
}
}
class AlternateDemo {
private int number = 1; //当前正在执行线程的标记,相当于状态标记
private Lock lock = new ReentrantLock();
private Condition condition1 = lock.newCondition();
private Condition condition2 = lock.newCondition();
private Condition condition3 = lock.newCondition();
public void loopA() {
lock.lock();
try {
//1. 判断
if (number != 1) {
condition1.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 2;
condition2.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopB() {
lock.lock();
try {
//1. 判断
if (number != 2) {
condition2.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 3;
condition3.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopC() {
lock.lock();
try {
//1. 判断
if (number != 3) {
condition3.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 1;
condition1.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
总结:1.与wait对比,wait方式需要依赖synchronized代码块，而condtion.wait()依赖Lock对象，并且代码更加灵活
2.condition.wait()可以将不同条件下的线程放入不同的等待队列,而单纯的wait()方法会将所有情况下的线程放入一个等待队列，这样在大量线程唤醒时会造成资源浪费
3.使用Lock对象进行同步，这样线程同步只需要依赖Lock对象,而使用原始的synchronized(this){}进行同步,需要依赖当前对象，笔者更喜欢Lock同步的方式