Added limit(), which will retain up to the first N elements of a Collection

git-svn-id: https://samskivert.googlecode.com/svn/trunk@2571 6335cc39-0255-0410-8fd6-9bcaacd3b74c

src/java/com/samskivert/util/CollectionUtil.java

@@ -72,6 +72,32 @@ public class CollectionUtil
         return col;
     }
 
+    /**
+     * Modify the specified Collection so that only the first <code>limit</code> elements
+     * remain, as determined by iteration order. If the Collection is smaller than limit,
+     * it is unmodified.
+     */
+    public static <T> void limit (Collection<T> col, int limit)
+    {
+        int size = col.size();
+        if (size > limit) {
+            if (col instanceof List) {
+                ((List) col).subList(limit, size).clear();
+
+            } else {
+                Iterator<T> itr = col.iterator();
+                int ii = 0;
+                for (; ii < limit; ii++) {
+                    itr.next();
+                }
+                for (; ii < size; ii++) {
+                    itr.next();
+                    itr.remove();
+                }
+            }
+        }
+    }
+
     /**
      * Returns a list containing a random selection of elements from the
      * specified collection. The total number of elements selected will be