--- a/gnv-artifacts/src/main/java/de/intevation/gnv/jfreechart/PolygonSeries.java	Fri Dec 25 12:00:14 2009 +0000
+++ b/gnv-artifacts/src/main/java/de/intevation/gnv/jfreechart/PolygonSeries.java	Sat Dec 26 15:32:08 2009 +0000
@@ -16,6 +16,15 @@
     protected CompactXYItems []  rings;
     protected Map                attributes;
 
+    private static long uniqueKey;
+
+    protected synchronized static Long createUniqueKey() {
+        return new Long(uniqueKey++);
+    }
+
+    public PolygonSeries() {
+        this(createUniqueKey(), null);
+    }
 
     public PolygonSeries(Comparable key, CompactXYItems [] rings) {
         this(key, null, rings, new HashMap());
@@ -49,6 +58,18 @@
         return rings;
     }
 
+    public void addRing(CompactXYItems newRing) {
+        if (rings == null) {
+            rings = new CompactXYItems [] { newRing };
+        }
+        else {
+            CompactXYItems [] nRings = new CompactXYItems[rings.length + 1];
+            System.arraycopy(rings, 0, nRings, 0, rings.length);
+            nRings[rings.length] = newRing;
+            rings = nRings;
+        }
+    }
+
     public void addRings(CompactXYItems [] newRings) {
         if (newRings == null || newRings.length == 0) {
             return;