Pluck of revision 45a25185236e38606e761060427ee8fa60144a8c from branch i2p.i2p.zzz.test

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    * netdb.jsp: Add country chart at bottom, clean up version chart

core/java/src/net/i2p/util/ObjectCounter.java

@@ -0,0 +1,42 @@
+package net.i2p.util;
+
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ *  Count things.
+ *
+ *  @author zzz
+ */
+public class ObjectCounter<K> {
+    private ConcurrentHashMap<K, Integer> _map;
+    public ObjectCounter() {
+        _map = new ConcurrentHashMap();
+    }
+    /**
+     *  Add one.
+     *  Not perfectly concurrent, new AtomicInteger(1) would be better,
+     *  at the cost of some object churn.
+     */
+    public void increment(K h) {
+        Integer i = _map.putIfAbsent(h, Integer.valueOf(1));
+        if (i != null)
+            _map.put(h, Integer.valueOf(i.intValue() + 1));
+    }
+    /**
+     *  @return current count
+     */
+    public int count(K h) {
+        Integer i = _map.get(h);
+        if (i != null)
+            return i.intValue();
+        return 0;
+    }
+    /**
+     *  @return set of objects with counts > 0
+     */
+    public Set<K> objects() {
+        return _map.keySet();
+    }
+}
+