Added a CountHashMap, which is used for maintaining a count of keys.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1622 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/util/CountHashMap.java

@@ -0,0 +1,53 @@
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001-2004 Michael Bayne
+// 
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.samskivert.util;
+
+import java.util.HashMap;
+
+/**
+ * A hashmap that maintains a count for each key.
+ *
+ * This implementation may change, but I find it useful to inherit all
+ * the goodness of clear(), keySet(), size(), etc.
+ */
+public class CountHashMap extends HashMap
+{
+    /**
+     * Increment the value associated with the specified key, return
+     * the new value.
+     */
+    public int incrementCount (Object key, int amount)
+    {
+        int[] val = (int[]) get(key);
+        if (val == null) {
+            put(key, val = new int[1]);
+        }
+        val[0] += amount;
+        return val[0];
+    }
+
+    /**
+     * Get the count associated with the specified key.
+     */
+    public int getCount (Object key)
+    {
+        int[] val = (int[]) get(key);
+        return (val == null) ? 0 : val[0];
+    }
+}