Utility routines for working with arrays.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@513 6335cc39-0255-0410-8fd6-9bcaacd3b74c
2001-12-14 18:57:36 +00:00
parent d8b9fbb48f
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+//
+// $Id: ArrayUtil.java,v 1.1 2001/12/14 18:57:36 shaper Exp $
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001 Walter Korman
+// 
+// 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.Random;
+
+/**
+ * Miscellaneous utility routines for working with arrays.
+ */
+public class ArrayUtil
+{
+    /**
+     * Shuffles the elements in the given array into a random sequence.
+     *
+     * @param values the array to shuffle.
+     */
+    public static void shuffle (int[] values)
+    {
+        shuffle(values, 0, values.length);
+    }
+
+    /**
+     * Shuffles a subset of elements within the specified array.
+     *
+     * @param values the array containing elements to shuffle.
+     * @param offset the index at which to start shuffling elements.
+     * @param length the number of elements to shuffle.
+     */
+    public static void shuffle (int[] values, int offset, int length)
+    {
+        for (int ii = (offset + length); ii > offset; ii--) {
+            int temp = values[ii - 1];
+            int idx = _rnd.nextInt(ii);
+            values[ii - 1] = values[idx];
+            values[idx] = temp;
+        }
+    }
+
+    /** The random object used when shuffling an array. */
+    protected static Random _rnd = new Random();
+}