blocks|key|403257|text|我在Guava中看不到类似的东西，但是围绕ArrayDeque构建的ForwardingQueue如何，您可以检查add()、offer()等上的容量，如果旧条目已经满了，则检查remove()旧条目。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|403258|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/7/docs/api/index.html?java/util/ArrayDeque.html|1|https://google.github.io/guava/releases/snapshot-jre/api/docs/com/google/common/collect/ForwardingQueue.html^0|L|A|Y|F|1L|5|1R|7|2H|8|L|A|0|Y|F|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@$9|10|A|11|1|12]|$9|13|A|14|1|15]]|E|$]]|$1|F|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]|N|$5|I|J|K|E|$L|O]]]]

I don't see anything like that in Guava, but how about a <a href="https://google.github.io/guava/releases/snapshot-jre/api/docs/com/google/common/collect/ForwardingQueue.html" rel="nofollow noreferrer"><code>ForwardingQueue</code></a> built around an <a href="http://docs.oracle.com/javase/7/docs/api/index.html?java/util/ArrayDeque.html" rel="nofollow noreferrer"><code>ArrayDeque</code></a> where you check the capacity on <code>add()</code>, <code>offer()</code>, etc. and <code>remove()</code> old entries if it's already full?

blocks|key|403266|text|Java's+ArrayBlockingQueue提供了一个固定大小的循环缓冲区。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|403267|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/ArrayBlockingQueue.html^0|7|I|0|P|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

<a href="http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/ArrayBlockingQueue.html" rel="nofollow">Java's <code>ArrayBlockingQueue</code></a> offers a fixed sized circular buffer.

blocks|key|403291|text|如果你想在泛型中使用Apache+(它包含了可用的CircularFifoBuffer<E>类)，Commons-Collections+with+Generics+(maven+link)是最好的选择。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|403292|另一方面，正如@FrankPavageau所说，你可以使用你自己的ForwardingQueue实现。一种简单的方法(有进一步优化的地方)应该是这样的：|403293|static+class+BoundedQueue<E>+extends+ForwardingQueue<E>+{

++private+final+Queue<E>+delegate;
++private+final+int+capacity;

++public+BoundedQueue(final+int+capacity)+{
++++this.delegate+=+
++++++++new+ArrayDeque<E>(capacity);+//+specifying+initial+capacity+is+optional
++++this.capacity+=+capacity;
++}

++@Override
++protected+Queue<E>+delegate()+{
++++return+delegate;
++}

++@Override
++public+boolean+add(final+E+element)+{
++++if+(size()+>=+capacity)+{
++++++delegate.poll();
++++}
++++return+delegate.add(element);
++}

++@Override
++public+boolean+addAll(final+Collection<?+extends+E>+collection)+{
++++return+standardAddAll(collection);
++}

++@Override
++public+boolean+offer(final+E+o)+{
++++return+standardOffer(o);
++}

}|code-block|syntax|javascript|403294|用法：|403295|final+BoundedQueue<Integer>+boundedQueue+=+new+BoundedQueue<Integer>(3);
boundedQueue.add(1);
System.out.println(boundedQueue);+//+[1]
boundedQueue.add(2);
System.out.println(boundedQueue);+//+[1,+2]
boundedQueue.add(3);
System.out.println(boundedQueue);+//+[1,+2,+3]
boundedQueue.add(4);
System.out.println(boundedQueue);+//+[2,+3,+4]
boundedQueue.addAll(Arrays.asList(5,+6,+7,+8));
System.out.println(boundedQueue);+//+[6,+7,+8]
((Queue<Integer>)+boundedQueue).offer(9);
System.out.println(boundedQueue);+//+[7,+8,+9]|403296|entityMap|0|LINK|mutability|MUTABLE|url|http://sourceforge.net/projects/collections/|1|http://mvnrepository.com/artifact/net.sourceforge.collections/collections-generic/4.01^0|P|L|1D|X|0|2C|A|1|0|X|F|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@$9|13|A|14|1|15]|$9|16|A|17|1|18]]|E|$]]|$1|F|3|G|5|6|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1D|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1E|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

<a href="http://sourceforge.net/projects/collections/" rel="nofollow">Commons-Collections with Generics</a> (<a href="http://mvnrepository.com/artifact/net.sourceforge.collections/collections-generic/4.01" rel="nofollow">maven link</a>) is the way to go if you want to use Apache Collections with generics (and it contains working <code>CircularFifoBuffer&lt;E&gt;</code> class).

On the other hand, as @FrankPavageau says, you can use your own <code>ForwardingQueue</code> implementatation. A naive approach (with place for further optimizations) would be something like this:

<pre><code>static class BoundedQueue&lt;E&gt; extends ForwardingQueue&lt;E&gt; {

 private final Queue&lt;E&gt; delegate;
 private final int capacity;

 public BoundedQueue(final int capacity) {
 this.delegate = 
 new ArrayDeque&lt;E&gt;(capacity); // specifying initial capacity is optional
 this.capacity = capacity;
 }

 @Override
 protected Queue&lt;E&gt; delegate() {
 return delegate;
 }

 @Override
 public boolean add(final E element) {
 if (size() &gt;= capacity) {
 delegate.poll();
 }
 return delegate.add(element);
 }

 @Override
 public boolean addAll(final Collection&lt;? extends E&gt; collection) {
 return standardAddAll(collection);
 }

 @Override
 public boolean offer(final E o) {
 return standardOffer(o);
 }

}
</code></pre>

Usage:

<pre><code>final BoundedQueue&lt;Integer&gt; boundedQueue = new BoundedQueue&lt;Integer&gt;(3);
boundedQueue.add(1);
System.out.println(boundedQueue); // [1]
boundedQueue.add(2);
System.out.println(boundedQueue); // [1, 2]
boundedQueue.add(3);
System.out.println(boundedQueue); // [1, 2, 3]
boundedQueue.add(4);
System.out.println(boundedQueue); // [2, 3, 4]
boundedQueue.addAll(Arrays.asList(5, 6, 7, 8));
System.out.println(boundedQueue); // [6, 7, 8]
((Queue&lt;Integer&gt;) boundedQueue).offer(9);
System.out.println(boundedQueue); // [7, 8, 9]
</code></pre>

blocks|key|403326|text|启动Guava15.0-您可以使用EvictingQueue|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|403327|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/google/guava/blob/master/guava/src/com/google/common/collect/EvictingQueue.java^0|H|D|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Starting Guava 15.0 - you can use <a href="https://github.com/google/guava/blob/master/guava/src/com/google/common/collect/EvictingQueue.java" rel="nofollow">EvictingQueue</a>

I need a data structure that can efficiently buffer a specific number of elements, in FIFO order.

As mentioned in <a href="https://stackoverflow.com/questions/5498865/size-limited-queue-that-holds-last-n-elements-in-java">this question</a>, Apache Commons has a CircularFifoBuffer, but it is sadly not generified. <a href="https://github.com/megamattron/collections-generic" rel="nofollow noreferrer">Some</a> <a href="http://wiki.apache.org/commons/Collections/GenericCollections" rel="nofollow noreferrer">forks</a> exist, but I'm not sure of their maintenance status.

Since Guava is the go-to library for my collection needs, I'm wondering: is there a good alternative in Guava? If not, should I implement it in my project, based on Apache Commons' CircularFifoBuffer?

Is there a Guava equivalent to Apache Commons CircularFifoBuffer?

数据结构

我需要一个数据结构，可以有效地缓冲特定数量的元素，在先进先出的顺序。正如在中提到的，Apache Commons有一个CircularFifoBuffer，但遗憾的是它没有泛化。 存在，但我不确定它们的维护状态。由于Guava是满足我的收藏需求的首选图书馆，我想知道:在Guava中有没有好的替代方案？如果没有，我是否应...

问有没有等同于Apache Commons CircularFifoBuffer的Guava？
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