LinkedBlockingQueue和ArrayBlockingQueue对比
LinkedBlockingQueue和ArrayBlockingQueue对比
IT云清
发布于 2019-01-22 15:10:41
发布于 2019-01-22 15:10:41
对比一下LinkedBlockingQueue和ArrayBlockingQueue的区别。
1.底层数据结构不同
LinkedBlockingQueue底层是单向链表，只有一个后继指针
/**
* Linked list node class
*/
static class Node<E> {
E item;
/**
* One of:
* - the real successor Node
* - this Node, meaning the successor is head.next
* - null, meaning there is no successor (this is the last node)
*/
Node<E> next;
Node(E x) { item = x; }
}ArrayBlockingQueue底层是数组
/** The queued items */
final Object[] items;2.队列大小
LinkedBlockingQueue的构造函数，可以显示指定队列大小，也可以不指定，不指定大小事，默认是Integer.MAX_VALUE，可以观察他的三个构造函数：
public LinkedBlockingQueue() {
this(Integer.MAX_VALUE);
}
public LinkedBlockingQueue(int capacity) {
if (capacity <= 0) throw new IllegalArgumentException();
this.capacity = capacity;
last = head = new Node<E>(null);
}
public LinkedBlockingQueue(Collection<? extends E> c) {
this(Integer.MAX_VALUE);
final ReentrantLock putLock = this.putLock;
putLock.lock(); // Never contended, but necessary for visibility
try {
int n = 0;
for (E e : c) {
if (e == null)
throw new NullPointerException();
if (n == capacity)
throw new IllegalStateException("Queue full");
enqueue(new Node<E>(e));
++n;
}
count.set(n);
} finally {
putLock.unlock();
}
}ArrayBlockingQueue的构造函数中，必须显示指定队列大小：
public ArrayBlockingQueue(int capacity) {
this(capacity, false);
}
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
this.items = new Object[capacity];
lock = new ReentrantLock(fair);
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
public ArrayBlockingQueue(int capacity, boolean fair,
Collection<? extends E> c) {
this(capacity, fair);
final ReentrantLock lock = this.lock;
lock.lock(); // Lock only for visibility, not mutual exclusion
try {
int i = 0;
try {
for (E e : c) {
checkNotNull(e);
items[i++] = e;
}
} catch (ArrayIndexOutOfBoundsException ex) {
throw new IllegalArgumentException();
}
count = i;
putIndex = (i == capacity) ? 0 : i;
} finally {
lock.unlock();
}
}3.使用的锁不同
LinkedBlockingQueue中，有两个锁，都是非公平锁：
/** Lock held by take, poll, etc */
private final ReentrantLock takeLock = new ReentrantLock();
/** Lock held by put, offer, etc */
private final ReentrantLock putLock = new ReentrantLock();ArrayBlockingQueue中，只有一个锁，默认是个非公平锁，也可以显示指定为公平锁：
/** Main lock guarding all access */
final ReentrantLock lock; public ArrayBlockingQueue(int capacity) {
this(capacity, false);//默认是非公平锁
}
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
this.items = new Object[capacity];
lock = new ReentrantLock(fair);
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
public ArrayBlockingQueue(int capacity, boolean fair,
Collection<? extends E> c) {
this(capacity, fair);
final ReentrantLock lock = this.lock;
lock.lock(); // Lock only for visibility, not mutual exclusion
try {
int i = 0;
try {
for (E e : c) {
checkNotNull(e);
items[i++] = e;
}
} catch (ArrayIndexOutOfBoundsException ex) {
throw new IllegalArgumentException();
}
count = i;
putIndex = (i == capacity) ? 0 : i;
} finally {
lock.unlock();
}
}本文参与 腾讯云自媒体分享计划，分享自作者个人站点/博客。
原始发表：2018年09月13日，如有侵权请联系 cloudcommunity@tencent.com 删除
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