diff --git a/src/main/java/cit/PureATN/DPenReceiver.java b/src/main/java/cit/PureATN/DPenReceiver.java
index 6d0685f..1939a2a 100644
--- a/src/main/java/cit/PureATN/DPenReceiver.java
+++ b/src/main/java/cit/PureATN/DPenReceiver.java
@@ -5,7 +5,6 @@
 import java.net.DatagramSocket;
 import java.net.SocketException;
 import java.text.SimpleDateFormat;
-import java.util.Date;
 import java.util.Hashtable;
 
 public class DPenReceiver implements Runnable {
diff --git a/src/main/java/cit/PureATN/MultiNote/MultiNote.java b/src/main/java/cit/PureATN/MultiNote/MultiNote.java
index f812047..8142641 100644
--- a/src/main/java/cit/PureATN/MultiNote/MultiNote.java
+++ b/src/main/java/cit/PureATN/MultiNote/MultiNote.java
@@ -1,7 +1,7 @@
 package cit.PureATN.MultiNote;
 
-import java.awt.Color;
 import java.awt.BasicStroke;
+import java.awt.Color;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.Iterator;
diff --git a/src/main/java/cit/PureATN/PenUser.java b/src/main/java/cit/PureATN/PenUser.java
index 5790414..b224208 100644
--- a/src/main/java/cit/PureATN/PenUser.java
+++ b/src/main/java/cit/PureATN/PenUser.java
@@ -8,10 +8,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
 import java.io.OutputStream;
 import java.io.Serializable;
-import java.net.SocketPermission;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Date;
@@ -24,8 +22,6 @@
 import org.piccolo2d.PNode;
 import org.piccolo2d.util.PObjectOutputStream;
 
-import cit.PureATN.MultiNote.MultiNote;
-
 public class PenUser implements Serializable {
 	private static final long serialVersionUID = 9212314123123L;
 	public static Hashtable<String, PenUser> penusers = new Hashtable<String, PenUser>();