--- /dev/null
+/*
+ * Copyright (c) 2003-2005 The BISON Project
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program 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 program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+package peersim.vector;
+
+import peersim.core.*;
+import java.util.*;
+
+/**
+ * This comparator class compares two node objects based on the value
+ * maintained by one of its protocols. The protocol must implement the
+ * {@link SingleValue} interface; its identifier has to be specified when a
+ * new comparator is built.
+ *
+ * @author Alberto Montresor
+ * @version $Revision: 1.4 $
+ */
+public class SingleValueComparator implements Comparator
+{
+
+/** Protocol to be be compared */
+private int pid;
+
+/**
+ * Builds a new comparator that compares the double values maintained
+ * by protocol identified by <code>pid</code>.
+ */
+public SingleValueComparator(int pid) { this.pid = pid; }
+
+/**
+ * Compares the values of two protocols. The parameters must have dynamic type
+ * {@link Node}. The protocol {@link #pid} is accessed on both nodes. These
+ * protocols have to implement the {@link SingleValue} interface. The values
+ * held by these protocol instances are then compared.
+ */
+public int compare(Object o1, Object o2)
+{
+ SingleValue s1 = (SingleValue) ((Node) o1).getProtocol(pid);
+ SingleValue s2 = (SingleValue) ((Node) o2).getProtocol(pid);
+ return (int) (s1.getValue() - s2.getValue());
+}
+
+}
