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BlockQueue.java
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BlockQueue.java
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package blockqueue;
import static com.google.common.base.Preconditions.*;
import net.jcip.annotations.ThreadSafe;
import java.util.AbstractQueue;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
* Created by fishdicks on 16/9/9.
*/
@ThreadSafe
public class BlockQueue<E> extends AbstractQueue<E> {
private final ReentrantLock lock = new ReentrantLock();
private final Condition notEmpty = lock.newCondition();
private final Condition notFull = lock.newCondition();
private Node head;
private Node last;
private final AtomicInteger count = new AtomicInteger(0);
private final int capacity;
public BlockQueue(int capacity) {
checkArgument(capacity > 0, "capacity must larger than 0");
this.capacity = capacity;
}
public BlockQueue() {
this(Integer.MAX_VALUE);
}
private static class Node<E> {
E item;
Node<E> next;
Node(E item) {
this.item = item;
}
}
@Override
public Iterator<E> iterator() {
return null;
}
@Override
public int size() {
return 0;
}
@Override
public boolean offer(E e) {
checkNotNull(e, "offer element can't be null");
if (count.get() == capacity) {
return false;
}
Node<E> node = new Node<E>(e);
int c = -1;
lock.lock();
try {
if (count.get() < capacity) {
enqueue(node);
c = count.getAndIncrement();
if (c+1 < capacity) {
notFull.signal();
}
}
} finally {
lock.unlock();
}
return c >= 0;
}
@Override
public E poll() {
return null;
}
@Override
public E peek() {
return null;
}
private void enqueue(BlockQueue.Node<E> node) {
last = last.next = node;
}
}