jodd.cache.FIFOCache Maven / Gradle / Ivy
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// Copyright (c) 2003-2014, Jodd Team (jodd.org). All Rights Reserved.
package jodd.cache;
import java.util.LinkedHashMap;
import java.util.Iterator;
/**
* FIFO (first in first out) cache.
*
*
* FIFO (first in first out): just adds items to the cache as they are accessed, putting them in a queue or buffer and
* not changing their location in the buffer; when the cache is full, items are ejected in the order they were
* added. Cache access overhead is constant time regardless of the size of the cache. The advantage of this algorithm
* is that it's simple and fast; it can be implemented using a simple array and an index. The disadvantage is that
* it's not very smart; it doesn't make any effort to keep more commonly used items in cache.
*
* Summary for FIFO: fast, not adaptive, not scan resistant.
*/
public class FIFOCache extends AbstractCacheMap {
public FIFOCache(int cacheSize) {
this(cacheSize, 0);
}
/**
* Creates a new LRU cache.
*/
public FIFOCache(int cacheSize, long timeout) {
this.cacheSize = cacheSize;
this.timeout = timeout;
cacheMap = new LinkedHashMap>(cacheSize + 1, 1.0f, false);
}
// ---------------------------------------------------------------- prune
/**
* Prune expired objects and, if cache is still full, the first one.
*/
@Override
protected int pruneCache() {
int count = 0;
CacheObject first = null;
Iterator> values = cacheMap.values().iterator();
while (values.hasNext()) {
CacheObject co = values.next();
if (co.isExpired() == true) {
values.remove();
count++;
}
if (first == null) {
first = co;
}
}
if (isFull()) {
if (first != null) {
cacheMap.remove(first.key);
count++;
}
}
return count;
}
}