--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/geo-backend/src/main/java/de/intevation/gnv/geobackend/util/RedundancyRemover.java	Tue Jan 26 16:33:36 2010 +0000
@@ -0,0 +1,56 @@
+package de.intevation.gnv.geobackend.util;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * @author Sascha L. Teichmann (sascha.teichmann@intevation.de)
+ */
+public final class RedundancyRemover
+extends            LinkedHashMap
+{
+    /** ceil(1029 * 1.75) = 1801, which is prime 
+     * -> suitable for a hash map slot size.
+     */
+    public static final int DEFAULT_LOOKBACK =
+        Integer.getInteger(
+            "de.intevation.gnv.geobackend.util.RedundancyRemover.lookback",
+            1029);
+
+    private int maxCapacity;
+    private int removed;
+
+    public RedundancyRemover() {
+        this(DEFAULT_LOOKBACK);
+    }
+
+    public RedundancyRemover(int maxCapacity) {
+        super((int)Math.ceil(maxCapacity * 1.75f));
+        this.maxCapacity = maxCapacity;
+    }
+
+    protected boolean removeEldestEntry(Map.Entry eldest) {
+        return size() > maxCapacity;
+    }
+
+    public int numRemoved() {
+        return removed;
+    }
+
+    public Object filter(Object object) {
+        if (object == null) {
+            return object;
+        }
+        Object old = get(object);
+
+        if (old != null) {
+            if (old != object) { // count only identical
+                ++removed;
+            }
+            return old;
+        }
+        put(object, object);
+        return object;
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :