问java.util.concurrent.BlockingQueue的实现

EN

public class DelayQueue<E extends Delayed> extends AbstractQueue<E>
implements BlockingQueue<E> {

private transient final ReentrantLock lock = new ReentrantLock();
private transient final Condition available = lock.newCondition();
private final PriorityQueue<E> q = new PriorityQueue<E>();

public boolean offer(E e) {
    **final ReentrantLock lock = this.lock;**//(*)
    lock.lock(); 
    try { ... }
    finally {lock.unlock();}

}

public E poll() {
    **final ReentrantLock lock = this.lock**;//(*)
    lock.lock(); 
    try { ... }
    finally {lock.unlock();}
 }}