sascha@555: package de.intevation.gnv.geobackend.util;
sascha@555: 
sascha@555: import java.util.LinkedHashMap;
sascha@555: import java.util.Map;
sascha@555: 
sascha@555: /**
sascha@555:  * @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
sascha@555:  */
sascha@555: public final class RedundancyRemover
sascha@555: extends            LinkedHashMap
sascha@555: {
sascha@555:     /** ceil(1029 * 1.75) = 1801, which is prime 
sascha@555:      * -> suitable for a hash map slot size.
sascha@555:      */
sascha@555:     public static final int DEFAULT_LOOKBACK =
sascha@555:         Integer.getInteger(
sascha@555:             "de.intevation.gnv.geobackend.util.RedundancyRemover.lookback",
sascha@555:             1029);
sascha@555: 
sascha@555:     private int maxCapacity;
sascha@555:     private int removed;
sascha@555: 
sascha@555:     public RedundancyRemover() {
sascha@555:         this(DEFAULT_LOOKBACK);
sascha@555:     }
sascha@555: 
sascha@555:     public RedundancyRemover(int maxCapacity) {
sascha@555:         super((int)Math.ceil(maxCapacity * 1.75f));
sascha@555:         this.maxCapacity = maxCapacity;
sascha@555:     }
sascha@555: 
sascha@555:     protected boolean removeEldestEntry(Map.Entry eldest) {
sascha@555:         return size() > maxCapacity;
sascha@555:     }
sascha@555: 
sascha@555:     public int numRemoved() {
sascha@555:         return removed;
sascha@555:     }
sascha@555: 
sascha@555:     public Object filter(Object object) {
sascha@555:         if (object == null) {
sascha@555:             return object;
sascha@555:         }
sascha@555:         Object old = get(object);
sascha@555: 
sascha@555:         if (old != null) {
sascha@555:             if (old != object) { // count only identical
sascha@555:                 ++removed;
sascha@555:             }
sascha@555:             return old;
sascha@555:         }
sascha@555:         put(object, object);
sascha@555:         return object;
sascha@555:     }
sascha@555: }
sascha@555: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :