Condition是Locks锁下的还有一种线程通信之间唤醒、堵塞的实现。它以下的await,和signal可以实现Object下的wait，notify和notifyAll的所有功能，除此之外改监视器和已绑定到每一个条件，可以实现多条件的监听。Condition实质是被绑定到一个锁上，腰围特定的Lock实例获得Condition，即用 newCondition()方法。
Condition下的await()相对于Object下的wait(); 堵塞或中断之前状况，让其处于等待状态。
Condition下的Signal();相当于Object下的notify();唤醒一个等待的状态。
Condition应用：
假设有一个缓存区，大小100，它支持put和take方法。假设试图在空的缓存区上运行take操作，则在某一项变得可用之前，线程一直堵塞；假设试图在满的缓存区上运行操作，则在有空间变得可用之前，线程一直讲堵塞。我们能够使用两个条件，一个记录缓存区的满，一个记录缓存区的空。
package andy.thread.test;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* @author Zhang,Tianyou
* @version 2014年11月9日 上午11:39:30
*/
public class ThreadConditiionBoundedBuffer {
public static void main(String[] args) {
BoundedBuffer buffer = new ThreadConditiionBoundedBuffer().new BoundedBuffer();
for (int i = 0; i < 100; i++) {
int task = i;
new Thread((new Runnable() {
public void run() {
try {
String putString = Thread.currentThread().getName() + task;
buffer.put(putString);
System.out.println(putString);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
})).start();
}
for (int i = 0; i < 100; i++) {
new Thread((new Runnable() {
public void run() {
try {
System.out.println( Thread.currentThread() + "take " + buffer.take());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
})).start();
}
}
class BoundedBuffer {
// 定义锁
Lock lock = new ReentrantLock();
Condition notFull = lock.newCondition(); // 没有满
Condition notEmpty = lock.newCondition(); // 不为空
Object[] items = new Object[100];
int putptr, takeptr, count;
public void put(Object x) throws InterruptedException {
lock.lock();
try {
// 假设已满 堵塞等待
while (count == items.length)
notFull.await();
// 假设未满运行以下 加入
items[putptr] = x;
if (++putptr == items.length)
putptr = 0;
++count;
// 唤醒读取缓冲的线程
notEmpty.signal();
} finally {
lock.unlock();
}
}
public Object take() throws InterruptedException {
lock.lock();
try {
// 假设为空 等待
while (count == 0)
notEmpty.await();
// 不为空按顺序去
Object x = items[takeptr];
if (++takeptr == items.length)
takeptr = 0;
--count;
notFull.signal();
return x;
} finally {
lock.unlock();
}
}
}
}
运行效果例如以下：
Thread-00 Thread-22 Thread-11 Thread-1414 Thread-1212 Thread-1010 Thread-88 Thread-66 Thread-44 Thread-1616 Thread-1818 Thread-77 Thread-2222 Thread-2020 Thread-55 Thread-33 Thread-2424 Thread-2626 Thread-99 Thread-2828 Thread-1313 Thread-3030 Thread-1717 Thread-1111 Thread-3232 Thread-1919 Thread-1515 Thread-2121 Thread-2323 Thread-2525 Thread-3434 Thread-3131 Thread-2727 Thread-3333 Thread-2929 Thread-3535 Thread-3636 Thread-3737 Thread-3838 Thread-4040 Thread-3939 Thread-4242 Thread-6464 Thread-6666 Thread-6262 Thread-6060 Thread-5858 Thread-4747 Thread-5656 Thread-4545 Thread-5050 Thread-4848 Thread-5252 Thread-4646 Thread-5454 Thread-4444 Thread-4343 Thread-6868 Thread-4141 Thread-7070 Thread-7272 Thread-7474 Thread-7676 Thread-4949 Thread-7878 Thread-6969 Thread-8080 Thread-7171 Thread-8282 Thread-7373 Thread-7575 Thread-8484 Thread-8686 Thread-7777 Thread-8888 Thread-8181 Thread-9090 Thread-8989 Thread-8383 Thread-7979 Thread-8787 Thread-8585 Thread-6767 Thread-9292 Thread-9191 Thread-6565 Thread-9494 Thread-6363 Thread-6161 Thread-9696 Thread-9898 Thread-5959 Thread-5757 Thread-5555 Thread-5353 Thread-9393 Thread-9595 Thread[Thread-100,5,main]take Thread-00 Thread-9999 Thread[Thread-101,5,main]take Thread-22 Thread[Thread-102,5,main]take Thread-11 Thread-9797 Thread[Thread-104,5,main]take Thread-44 Thread[Thread-106,5,main]take Thread-66 Thread[Thread-108,5,main]take Thread-88 Thread[Thread-110,5,main]take Thread-1010 Thread-5151 Thread[Thread-112,5,main]take Thread-1212 Thread[Thread-114,5,main]take Thread-1616 Thread[Thread-116,5,main]take Thread-1818 Thread[Thread-118,5,main]take Thread-77 Thread[Thread-120,5,main]take Thread-2020 Thread[Thread-122,5,main]take Thread-2222 Thread[Thread-124,5,main]take Thread-55 Thread[Thread-103,5,main]take Thread-1414 Thread[Thread-126,5,main]take Thread-33 Thread[Thread-128,5,main]take Thread-2424 Thread[Thread-105,5,main]take Thread-2626 Thread[Thread-130,5,main]take Thread-99 Thread[Thread-107,5,main]take Thread-2828 Thread[Thread-132,5,main]take Thread-1313 Thread[Thread-109,5,main]take Thread-3030 Thread[Thread-134,5,main]take Thread-1515 Thread[Thread-111,5,main]take Thread-1111 Thread[Thread-136,5,main]take Thread-1717 Thread[Thread-113,5,main]take Thread-3232 Thread[Thread-138,5,main]take Thread-1919 Thread[Thread-140,5,main]take Thread-2121 Thread[Thread-115,5,main]take Thread-2323 Thread[Thread-142,5,main]take Thread-2525 Thread[Thread-117,5,main]take Thread-3434 Thread[Thread-144,5,main]take Thread-3131 Thread[Thread-119,5,main]take Thread-2727 Thread[Thread-146,5,main]take Thread-2929 Thread[Thread-148,5,main]take Thread-3333 Thread[Thread-121,5,main]take Thread-3535 Thread[Thread-150,5,main]take Thread-3636 Thread[Thread-152,5,main]take Thread-3737 Thread[Thread-123,5,main]take Thread-4040 Thread[Thread-125,5,main]take Thread-3838 Thread[Thread-127,5,main]take Thread-3939 Thread[Thread-154,5,main]take Thread-4242 Thread[Thread-129,5,main]take Thread-6666 Thread[Thread-156,5,main]take Thread-6464 Thread[Thread-131,5,main]take Thread-6262 Thread[Thread-158,5,main]take Thread-6060 Thread[Thread-160,5,main]take Thread-5656 Thread[Thread-137,5,main]take Thread-4545 Thread[Thread-133,5,main]take Thread-5858 Thread[Thread-135,5,main]take Thread-4747 Thread[Thread-162,5,main]take Thread-5454 Thread[Thread-139,5,main]take Thread-5252 Thread[Thread-164,5,main]take Thread-5050 Thread[Thread-143,5,main]take Thread-4646 Thread[Thread-141,5,main]take Thread-4848 Thread[Thread-145,5,main]take Thread-4444 Thread[Thread-166,5,main]take Thread-4343 Thread[Thread-147,5,main]take Thread-6868 Thread[Thread-168,5,main]take Thread-4141 Thread[Thread-157,5,main]take Thread-7070 Thread[Thread-151,5,main]take Thread-7272 Thread[Thread-170,5,main]take Thread-7474 Thread[Thread-155,5,main]take Thread-7676 Thread[Thread-153,5,main]take Thread-4949 Thread[Thread-172,5,main]take Thread-7878 Thread[Thread-149,5,main]take Thread-6969 Thread[Thread-174,5,main]take Thread-8080 Thread[Thread-159,5,main]take Thread-7171 Thread[Thread-176,5,main]take Thread-8282 Thread[Thread-161,5,main]take Thread-7373 Thread[Thread-163,5,main]take Thread-7575 Thread[Thread-178,5,main]take Thread-8484 Thread[Thread-165,5,main]take Thread-8686 Thread[Thread-167,5,main]take Thread-7777 Thread[Thread-180,5,main]take Thread-8888 Thread[Thread-182,5,main]take Thread-8181 Thread[Thread-169,5,main]take Thread-9090 Thread[Thread-184,5,main]take Thread-8989 Thread[Thread-171,5,main]take Thread-8383 Thread[Thread-173,5,main]take Thread-7979 Thread[Thread-189,5,main]take Thread-8585 Thread[Thread-183,5,main]take Thread-6161 Thread[Thread-192,5,main]take Thread-5959 Thread[Thread-187,5,main]take Thread-9898 Thread[Thread-185,5,main]take Thread-9696 Thread[Thread-179,5,main]take Thread-6363 Thread[Thread-194,5,main]take Thread-5757 Thread[Thread-181,5,main]take Thread-9494 Thread[Thread-190,5,main]take Thread-6565 Thread[Thread-177,5,main]take Thread-9191 Thread[Thread-196,5,main]take Thread-5555 Thread[Thread-175,5,main]take Thread-9292 Thread[Thread-188,5,main]take Thread-6767 Thread[Thread-191,5,main]take Thread-5353 Thread[Thread-198,5,main]take Thread-9393 Thread[Thread-186,5,main]take Thread-8787 Thread[Thread-193,5,main]take Thread-9595 Thread[Thread-195,5,main]take Thread-9999 Thread[Thread-197,5,main]take Thread-9797 Thread[Thread-199,5,main]take Thread-5151