diff --git a/examples/src/main/java/edu/umd/cs/piccolo/examples/ShadowExample.java b/examples/src/main/java/edu/umd/cs/piccolo/examples/ShadowExample.java
index 7c68e3e..6793ccd 100755
--- a/examples/src/main/java/edu/umd/cs/piccolo/examples/ShadowExample.java
+++ b/examples/src/main/java/edu/umd/cs/piccolo/examples/ShadowExample.java
@@ -28,10 +28,8 @@
  */
 package edu.umd.cs.piccolo.examples;
 
-import java.awt.BasicStroke;
 import java.awt.Color;
 import java.awt.Graphics2D;
-import java.awt.Image;
 import java.awt.Paint;
 
 import java.awt.image.BufferedImage;
@@ -51,6 +49,10 @@
  */
 public final class ShadowExample extends PFrame {
 
+    /** Default serial version UID. */
+    private static final long serialVersionUID = 1L;
+
+
     /**
      * Create a new shadow example.
      */
diff --git a/extras/src/main/java/edu/umd/cs/piccolox/nodes/PShadow.java b/extras/src/main/java/edu/umd/cs/piccolox/nodes/PShadow.java
index c6683a0..10a1d1c 100755
--- a/extras/src/main/java/edu/umd/cs/piccolox/nodes/PShadow.java
+++ b/extras/src/main/java/edu/umd/cs/piccolox/nodes/PShadow.java
@@ -31,8 +31,6 @@
 import java.awt.Image;
 import java.awt.Paint;
 
-import java.awt.image.BufferedImage;
-
 import edu.umd.cs.piccolo.nodes.PImage;
 
 import edu.umd.cs.piccolox.util.ShadowUtils;
@@ -42,6 +40,10 @@
  */
 public final class PShadow extends PImage {
 
+    /** Default serial version UID. */
+    private static final long serialVersionUID = 1L;
+
+
     /**
      * Create a new shadow node containing a shadow of the specified source image using the
      * specified shadow paint and gaussian blur radius.  The dimensions of this node will be
diff --git a/extras/src/test/java/edu/umd/cs/piccolox/nodes/PShadowTest.java b/extras/src/test/java/edu/umd/cs/piccolox/nodes/PShadowTest.java
index 86874f7..8739373 100755
--- a/extras/src/test/java/edu/umd/cs/piccolox/nodes/PShadowTest.java
+++ b/extras/src/test/java/edu/umd/cs/piccolox/nodes/PShadowTest.java
@@ -30,7 +30,6 @@
 
 import java.awt.Color;
 import java.awt.Graphics2D;
-import java.awt.Image;
 import java.awt.Paint;
 
 import java.awt.image.BufferedImage;
@@ -59,21 +58,21 @@
         }
 
         try {
-            PShadow shadowNode = new PShadow(null, shadowPaint, 4);
+            new PShadow(null, shadowPaint, 4);
             fail("ctr(null, ...) expected IllegalArgumentException");
         }
         catch (IllegalArgumentException e) {
             // expected
         }
         try {
-            PShadow shadowNode = new PShadow(src, shadowPaint, 0);
+            new PShadow(src, shadowPaint, 0);
             fail("ctr(..., -1) expected IllegalArgumentException");
         }
         catch (IllegalArgumentException e) {
             // expected
         }
         try {
-            PShadow shadowNode = new PShadow(src, shadowPaint, -1);
+            new PShadow(src, shadowPaint, -1);
             fail("ctr(..., -1) expected IllegalArgumentException");
         }
         catch (IllegalArgumentException e) {
diff --git a/extras/src/test/java/edu/umd/cs/piccolox/util/ShadowUtilsTest.java b/extras/src/test/java/edu/umd/cs/piccolox/util/ShadowUtilsTest.java
index 5f3139d..fb97617 100755
--- a/extras/src/test/java/edu/umd/cs/piccolox/util/ShadowUtilsTest.java
+++ b/extras/src/test/java/edu/umd/cs/piccolox/util/ShadowUtilsTest.java
@@ -30,7 +30,6 @@
 
 import java.awt.Color;
 import java.awt.Graphics2D;
-import java.awt.Image;
 import java.awt.Paint;
 
 import java.awt.image.BufferedImage;