读者-写者问题的写者优先算法全部代码
时间: 2023-12-21 21:06:17 浏览: 37
下面是完整的Java实现读者-写者问题的写者优先算法:
```
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class WriterPriorityReadWriteLock {
private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
private final ReentrantReadWriteLock.WriteLock writeLock = lock.writeLock();
private final ReentrantReadWriteLock.ReadLock readLock = lock.readLock();
private int readers = 0;
private int writers = 0;
private int writeRequests = 0;
public void startRead() throws InterruptedException {
readLock.lock();
try {
while (writers > 0 || writeRequests > 0) {
wait();
}
readers++;
} finally {
readLock.unlock();
}
}
public void endRead() {
readLock.lock();
try {
readers--;
notifyAll();
} finally {
readLock.unlock();
}
}
public void startWrite() throws InterruptedException {
writeLock.lock();
try {
writeRequests++;
while (readers > 0 || writers > 0) {
wait();
}
writeRequests--;
writers++;
} finally {
writeLock.unlock();
}
}
public void endWrite() {
writeLock.lock();
try {
writers--;
notifyAll();
} finally {
writeLock.unlock();
}
}
}
```
在这个实现中,读者和写者线程都可以通过调用startRead()和startWrite()方法来获取锁定,然后通过调用endRead()和endWrite()方法来释放锁定。在写者优先算法中,如果存在等待的写者,则新的读者线程必须等待所有等待的写者完成。
需要注意的是,如果有多个写者在等待锁定,则它们将按照先来先服务的顺序获得锁定。因此,这种实现可能会导致饥饿现象,即某些线程可能会无限期地等待。为了避免这种情况,可以采用其他的算法,例如读者优先算法或者公平算法。