public class semaphoreTest {
static LinkedList<Integer> integerLinkedList = new LinkedList<>();
static Semaphore semaphore = new Semaphore(1);
static Object lock = new Object();
public static void main(String[] args) throws InterruptedException {
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
try {
produce();
} catch (InterruptedException e) {
}
}
});
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
try {
consume();
} catch (InterruptedException e) {
}
}
});
t1.start();
t2.start();
t1.join();
t2.join();
}
private static void produce() throws InterruptedException {
semaphore.acquire();
int value = 0;
while (true) {
while (integerLinkedList.size() == 10) {
semaphore.release();
}
integerLinkedList.add(value++);
}
}
private static void consume() throws InterruptedException {
semaphore.acquire();
while (true) {
while (integerLinkedList.size() == 0) {
semaphore.release();
}
//semaphore.release();
Integer value = integerLinkedList.removeFirst();
System.out.println("Size of the List is " + integerLinkedList.size() + " and value removed is " + value);
semaphore.release();
Thread.sleep(100);
}
}
}
这是我尝试使用信号量作为锁写入的生产者消费者问题。但是在几乎删除240个元素之后,我无法弄清楚它会给出Maximum permit count exceeded
的错误消息。
我在正确的地方释放锁,但无法弄清楚它的获取部分有什么问题。
错误消息如下:
Exception in thread "Thread-0" java.lang.Error: Maximum permit count exceeded
at java.util.concurrent.Semaphore$Sync.tryReleaseShared(Semaphore.java:192)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(AbstractQueuedSynchronizer.java:1341)
at java.util.concurrent.Semaphore.release(Semaphore.java:426)
at interviewQuestions.semaphoreTest.procude(semaphoreTest.java:53)
at interviewQuestions.semaphoreTest.access$000(semaphoreTest.java:12)
at interviewQuestions.semaphoreTest$1.run(semaphoreTest.java:23)
at java.lang.Thread.run(Thread.java:745)
Exception in thread "Thread-1" java.lang.Error: Maximum permit count exceeded
at java.util.concurrent.Semaphore$Sync.tryReleaseShared(Semaphore.java:192)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(AbstractQueuedSynchronizer.java:1341)
at java.util.concurrent.Semaphore.release(Semaphore.java:426)
at interviewQuestions.semaphoreTest.consume(semaphoreTest.java:72)
at interviewQuestions.semaphoreTest.access$100(semaphoreTest.java:12)
at interviewQuestions.semaphoreTest$2.run(semaphoreTest.java:33)
at java.lang.Thread.run(Thread.java:745)
答案 0 :(得分:5)
问题是 您释放的信号量比获得的信号量多 。您应该删除 while
以释放您的信号量。您应该只发布一次,因此请改用 if
。
根据您的计划produce()
和consume()
应该更改为此。
<强> 农产品() 强>
private static void produce() throws InterruptedException {
int value = 0;
while (true) {
//try to get control & put an item.
semaphore.acquire();
//but if the queue is full, give up and try again.
if (integerLinkedList.size() == 10) {
semaphore.release();
continue;
}
//if not full, put an item & release the control.
integerLinkedList.add(value++);
semaphore.release();
}
}
<强> 消耗() 强>
private static void consume() throws InterruptedException {
while (true) {
//try to get the control and consume an item.
semaphore.acquire();
//but if the queue is empty, give up and try again.
if (integerLinkedList.size() == 0) {
semaphore.release();
continue;
}
//if not empty, *consume first one, *print it, *release the control and go sleep.
Integer value = integerLinkedList.removeFirst();
System.out.println("Size of the List is " + integerLinkedList.size() + " and value removed is " + value);
semaphore.release();
Thread.sleep(100);
}
}
如果您希望处于更安全的一方,可以在每个Thread.sleep(50);
语句之前添加break;
之类的内容,这样您就可以给其他线程一些时间来继续执行它。
我认为你编制了典型的生产者消费者问题。如果您想让我改变一下,请告诉我。无论如何希望这可以解决你的基本问题。 :))
答案 1 :(得分:0)
虽然@Supun的答案是正确的,但我需要线程无限期运行。因此我找到了解决方案。
public void produces() throws InterruptedException {
int value = 0;
while (true){
semaphore.acquire();
if(integerList.size() != 10 ) {
integerList.add(value++);
}
semaphore.release();
}
}
public void consumes() throws InterruptedException {
Thread.sleep(100);
semaphore.acquire();
while (true){
Integer take = integerList.removeFirst();
System.out.println("Size of the BlockingQueue is : "+ integerList.size()+" and the value consumed is :"+take);
Thread.sleep(100);
semaphore.release();
}
}