--- a/rep/channel/NetworkSimulator.java	Thu Aug 28 14:39:34 2008 +0900
+++ b/rep/channel/NetworkSimulator.java	Thu Aug 28 15:05:14 2008 +0900
@@ -3,13 +3,17 @@
 import java.util.LinkedList;
 
 
-public class NetworkSimulator<P> {
+public class NetworkSimulator<P> extends REPLogger {
 	public static NetworkSimulator<?> ns;
-	synchronized public static <T> NetworkSimulator<T> singleton(){
+	
+	public static <T> NetworkSimulator<?> singleton(){
+		// double check singleton
 		if (ns==null)
-			ns = new NetworkSimulator<T>();
-		return (NetworkSimulator<T>) ns;
-		// NetworkSimulator<Obj> ns = NetworkSimulator.singleton(new NetworkSimulator<Obj>());
+			synchronized (NetworkSimulator.class) {
+				if (ns==null) 
+					ns = new NetworkSimulator<T>();
+			}
+		return ns;
 	}
 
 	int logLevel=5;
@@ -92,22 +96,6 @@
 		}
 	}
 	
-	/** simulation log command */
-	synchronized public void writeLog(String log, int level){
-		if ( level<=logLevel )
-			System.out.println(log);
-		System.out.flush();
-	}
-	public void writeLog(String log){
-		writeLog(log, 0);
-	}
-	public void writeLog(Thread thr, String log, int level){
-		writeLog(thr.getName()+": "+log, level);
-	}
-	public void setLogLevel(int logLevel) {
-		this.logLevel = logLevel;
-	}
-
 
 }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rep/channel/REPLogger.java	Thu Aug 28 15:05:14 2008 +0900
@@ -0,0 +1,22 @@
+package rep.channel;
+
+public class REPLogger {
+
+	private int logLevel;
+	/** simulation log command */
+	synchronized public void writeLog(String log, int level){
+		if ( level<=logLevel )
+			System.out.println(log);
+		System.out.flush();
+	}
+	public void writeLog(String log){
+		writeLog(log, 0);
+	}
+	public void writeLog(Thread thr, String log, int level){
+		writeLog(thr.getName()+": "+log, level);
+	}
+	public void setLogLevel(int logLevel) {
+		this.logLevel = logLevel;
+	}
+
+}