Helfer CacheBounded

Jan Burse, erstellt 15. Sep 2018
package matula.util.system;
import matula.util.data.MapEntry;
import matula.util.data.MapHashLink;
/**
* <p>This class provides an unsynchronized LRU cache.</p>
* <p/>
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
* <p/>
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
* <p/>
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
* <p/>
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
* <p/>
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
*/
public final class CacheBounded<K, V> extends MapHashLink<K, V> {
public static final int DEFAULT_MAX = 100;
private int max;
/**
* <p>Create a new cache.</p>
*/
public CacheBounded() {
this(DEFAULT_MAX);
}
/**
* <p>Create a new cache.</p>
*
* @param m The max size.
*/
public CacheBounded(int m) {
max = m;
}
/**
* <p>Set the max size.</p>
*
* @param m The max size.
*/
public void setMax(int m) {
if (m < 0)
throw new IllegalArgumentException("negative max");
while (m < size)
removeEntry(getFirstEntry());
resize();
max = m;
}
/**
* <p>Add the key to the map.</p>
* <p>Assumption is that key is not yet present.</p>
* <p>Entry is create at the bottom.</p>
* <p>Superflows entry at the top is removed.</p>
*
* @param f The entry.
*/
public void putEntry(MapEntry<K, V> f) {
super.putEntry(f);
if (max < size)
removeEntry(getFirstEntry());
}
/**
* <p>Find the key in the map.</p>
* <p>If there is a hit, then move pair to botton.</p>
*
* @param key The key.
* @return The entry.
*/
public MapEntry<K, V> getEntry(K key) {
MapEntry<K, V> pair = super.getEntry(key);
if (pair != null) {
removeEntry(pair);
super.putEntry(pair);
}
return pair;
}
}

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