Java Concurrency 简明教程
Java Concurrency - Condition Interface
java.util.concurrent.locks.Condition 接口为线程提供暂停其执行的能力，直到给定的条件为真。一个 Condition 对象必然绑定到一个 Lock，并且通过 newCondition() 方法获得。
Condition Methods
以下是 Condition 类中可用的重要方法列表。
Sr.No. |
Method & Description |
1 |
public void await() 导致当前线程等待，直到它被信号或中断。 |
2 |
public boolean await(long time, TimeUnit unit) 导致当前线程等待，直到它被信号或中断，或指定的等待时间经过。 |
3 |
public long awaitNanos(long nanosTimeout) 导致当前线程等待，直到它被信号或中断，或指定的等待时间经过。 |
4 |
public long awaitUninterruptibly() 导致当前线程等待，直到它被信号。 |
5 |
public long awaitUntil() 让当前线程等待，直到它被发出信号或被中断，或者指定的截止时间经过。 |
6 |
public void signal() 唤醒一个等待中的线程。 |
7 |
public void signalAll() 唤醒所有等待中的线程。 |
Example
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class TestThread {
public static void main(String[] args) throws InterruptedException {
ItemQueue itemQueue = new ItemQueue(10);
//Create a producer and a consumer.
Thread producer = new Producer(itemQueue);
Thread consumer = new Consumer(itemQueue);
//Start both threads.
producer.start();
consumer.start();
//Wait for both threads to terminate.
producer.join();
consumer.join();
}
static class ItemQueue {
private Object[] items = null;
private int current = 0;
private int placeIndex = 0;
private int removeIndex = 0;
private final Lock lock;
private final Condition isEmpty;
private final Condition isFull;
public ItemQueue(int capacity) {
this.items = new Object[capacity];
lock = new ReentrantLock();
isEmpty = lock.newCondition();
isFull = lock.newCondition();
}
public void add(Object item) throws InterruptedException {
lock.lock();
while(current >= items.length)
isFull.await();
items[placeIndex] = item;
placeIndex = (placeIndex + 1) % items.length;
++current;
//Notify the consumer that there is data available.
isEmpty.signal();
lock.unlock();
}
public Object remove() throws InterruptedException {
Object item = null;
lock.lock();
while(current <= 0) {
isEmpty.await();
}
item = items[removeIndex];
removeIndex = (removeIndex + 1) % items.length;
--current;
//Notify the producer that there is space available.
isFull.signal();
lock.unlock();
return item;
}
public boolean isEmpty() {
return (items.length == 0);
}
}
static class Producer extends Thread {
private final ItemQueue queue;
public Producer(ItemQueue queue) {
this.queue = queue;
}
@Override
public void run() {
String[] numbers =
{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"};
try {
for(String number: numbers) {
System.out.println("[Producer]: " + number);
}
queue.add(null);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
static class Consumer extends Thread {
private final ItemQueue queue;
public Consumer(ItemQueue queue) {
this.queue = queue;
}
@Override
public void run() {
try {
do {
Object number = queue.remove();
System.out.println("[Consumer]: " + number);
if(number == null) {
return;
}
} while(!queue.isEmpty());
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
}这将产生以下结果。