ccse(CountDownLatch,CycliBarrier,Semaplore,Exchanger)
关于等待状态的线程调用interrupt方法报异常：InterruptedException
当线程被阻塞，比如wait，join，sleep等，在调用interrupt方法，没有占用cpu运行的线程是不可能给自己的中断状态置位的，这就产生了InterruptedException异常.
一.闭锁CountDownLatch(允许一个或多个线程等待其它线程完成操作)
代码实例：
package com.thread.ccse;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* Created by IntelliJ IDEA.
* User: 周强
* Description:
* Date: 2017/8/9
* Time: 21:04
*/
public class CountDownLatchTest {
public static CountDownLatch c = new CountDownLatch(4);
public static void main(String [] args) throws InterruptedException {
Thread t =new Thread(new Runnable() {
@Override
public void run() {
System.out.println(c.getCount()); //第1
c.countDown();
System.out.println(c.getCount());//第2
c.countDown();
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(c.getCount());//第3
c.countDown();
System.out.println(c.getCount());//第4
}
});
t.start();
c.await(2, TimeUnit.SECONDS);
c.countDown();
System.out.println(c.getCount( ));//第5
}
}
输出结果如下：
Connected to the target VM, address: '127.0.0.1:55816', transport: 'socket' 4 第1 3 第2 1 第5 Disconnected from the target VM, address: '127.0.0.1:55816', transport: 'socket' 1 第3 0 第4 Process finished with exit code 0
由于线程t沉睡时间大于CountDownLatch c的等待时间，所以线程t在主线证执行完毕后才结束的.
二：栅栏CyclicBarrier(指定线程数，必须在该线程数内的线程全部到达同步点，才继续往下执行)
示例代码：
package com.thread.ccse;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
/**
* Created by IntelliJ IDEA.
* User: 周强
* Description:
* Date: 2017/8/9
* Time: 21:30
*/
public class CyclicBarrierTest {
static Thread t = new Thread(new Runnable() {
@Override
public void run() {
System.out.println("3");
}
});
static Thread thread = null;
public static CyclicBarrier c = new CyclicBarrier(2,t);
static {
thread = new Thread(new Runnable() {
@Override
public void run() {
try {
c.await();
System.out.println("1");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
}
});
}
public static void main(String [] args){
thread.start();
try {
c.await();
System.out.println("2");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (BrokenBarrierException e) {
e.printStackTrace();
}
}
}
执行结果：
Disconnected from the target VM, address: '127.0.0.1:56157', transport: 'socket' 3 2 1//其中，3 肯定是最先输出的，1 和 2 的输出顺序是不一定的 Process finished with exit code 0
CountDownLatch和CyclicBarrier的区别：
CountDownLatch计数器只能使用一次，而CyclicBarrier的计数器可以使用多次，因为CyclicBarrier可以使用reset方法重置计数器；
CyclicBarrier还提供其它方法，如getNumberWating方法可以获得CyclicBarrier阻塞的线程数，isBroken方法可以用来了解阻塞的线程是否被中断。
三：有界容器Semaphore(构造固定长度的资源池)
代码示例：
package com.thread;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Semaphore;
/**
* Created by 周强 on 2017/8/10.
*/
public class SemaphoreTest {
public static Semaphore s = new Semaphore(1);
public static volatile int i =1;
public static List<String> list = new ArrayList();
public static void main(String [] args) throws InterruptedException {
Thread a = new Thread(new ta());
Thread b = new Thread(new tb());
s.acquire(); //消费唯一许可；
a.start();
b.start();
}
static class ta implements Runnable{
@Override
public void run() {
System.out.println("开始");
try {
s.acquire(); //唯一许可已被消费了，此处被阻塞
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(i);
list.add(String.valueOf(i));
i++;
System.out.println("开始---end");
}
}
static class tb implements Runnable{
@Override
public void run() {
System.out.println("acquire");
list.remove(String.valueOf(i));
System.out.println(list.toString());
s.release();、//释放许可
}
}
}
执行结果：
Disconnected from the target VM, address: '127.0.0.1:65218', transport: 'socket' 开始 acquire [] 1 开始---end Process finished with exit code 0
四.（线程同步）Exchanger（）
代码示例：
package com.thread;
import java.util.concurrent.Exchanger;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* Created by 周强 on 2017/8/10.
*/
public class ExchangerTest {
public static Exchanger<String> exgr = new Exchanger<String>();
public static ExecutorService threadPool = Executors.newFixedThreadPool(2);
public static void main(String [] args){
threadPool.execute(new Runnable() { //线程A
@Override
public void run() {
String a = "a";
try {
exgr.exchange(a);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("a ="+a );
}
});
threadPool.execute(new Runnable() { //线程B
@Override
public void run() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
String b = "b";
String a = null;
try {
a = exgr.exchange("b");
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("a ="+a +" "+"b ="+b);
}
});
threadPool.shutdown();
}
}
执行结果：
结果一：
Connected to the target VM, address: '127.0.0.1:49408', transport: 'socket' a =a b =b
a =a Disconnected from the target VM, address: '127.0.0.1:49408', transport: 'socket'
结果二：
Connected to the target VM, address: '127.0.0.1:49524', transport: 'socket'
a =a
a =a b =b
Disconnected from the target VM, address: '127.0.0.1:49524', transport: 'socket'
结论：虽然线程B沉睡了1秒，但由于线程A和B都在exgr.exchange处阻塞了，互相等待，且阻塞后的只剩下了打印的操作，所以，打印操作的先后顺序并能确定.
Exchanger（交换者）是一个用于线程间协作的工具类。Exchanger用于进行线程间的数据交换。它提供一个同步点，在这个同步点两个线程可以交换彼此的数据。这两个线程通过exchange方法交换数据， 如果第一个线程先执行exchange方法，它会一直等待第二个线程也执行exchange，当两个线程都到达同步点时，这两个线程就可以交换数据，将本线程生产出来的数据传递给对方。
以上为本次学习 闭锁（CountDownLatch）,栅栏（CyclicBarrier），有界容器（Semaphore）和线程同步工具类（Exchange）四个多线程相关工具类的代码笔记，工作中没有使用过，权且学习积累，以备后用。
//线程A
