diff --git a/java/src/processing/mode/java/DebugTree.java b/java/src/processing/mode/java/ASTViewer.java
similarity index 98%
rename from java/src/processing/mode/java/DebugTree.java
rename to java/src/processing/mode/java/ASTViewer.java
index 7bccaadd0..a321f7c4a 100644
--- a/java/src/processing/mode/java/DebugTree.java
+++ b/java/src/processing/mode/java/ASTViewer.java
@@ -24,13 +24,13 @@ import processing.app.ui.ZoomTreeCellRenderer;
 import processing.mode.java.PreprocessedSketch.SketchInterval;
 
 
-class DebugTree {
+class ASTViewer {
   final JDialog window;
   final JTree tree;
   final Consumer<PreprocessedSketch> updateListener;
 
 
-  DebugTree(JavaEditor editor, PreprocessingService pps) {
+  ASTViewer(JavaEditor editor, PreprocessingService pps) {
     updateListener = this::buildAndUpdateTree;
 
     window = new JDialog(editor);
diff --git a/java/src/processing/mode/java/JavaEditor.java b/java/src/processing/mode/java/JavaEditor.java
index 3cb9f959d..85459b235 100644
--- a/java/src/processing/mode/java/JavaEditor.java
+++ b/java/src/processing/mode/java/JavaEditor.java
@@ -90,6 +90,10 @@ public class JavaEditor extends Editor {
   protected PreprocessingService preprocessingService;
   protected PDEX pdex;
 
+  // set true to show AST debugging window
+  static private final boolean SHOW_AST_VIEWER = false;
+  private ASTViewer astViewer;
+
 
   protected JavaEditor(Base base, String path, EditorState state,
                        Mode mode) throws EditorException {
@@ -128,6 +132,10 @@ public class JavaEditor extends Editor {
     preprocessingService = new PreprocessingService(this);
     pdex = new PDEX(this, preprocessingService);
 
+    if (SHOW_AST_VIEWER) {
+      astViewer = new ASTViewer(this, preprocessingService);
+    }
+
     Toolkit.setMenuMnemonics(textarea.getRightClickPopup());
 
     // ensure completion is hidden when editor loses focus
@@ -1338,6 +1346,9 @@ public class JavaEditor extends Editor {
     }
     preprocessingService.dispose();
     pdex.dispose();
+    if (astViewer != null) {
+      astViewer.dispose();
+    }
     super.dispose();
   }
 
diff --git a/java/src/processing/mode/java/PDEX.java b/java/src/processing/mode/java/PDEX.java
index 4778f331c..03b2a5379 100644
--- a/java/src/processing/mode/java/PDEX.java
+++ b/java/src/processing/mode/java/PDEX.java
@@ -8,8 +8,6 @@ import processing.app.SketchCode;
 
 
 public class PDEX {
-  static private final boolean SHOW_DEBUG_TREE = false;
-
   private boolean enabled = true;
 
   private ErrorChecker errorChecker;
@@ -17,7 +15,6 @@ public class PDEX {
   private InspectMode inspect;
   private ShowUsage usage;
   private Rename rename;
-  private DebugTree debugTree;
 
   private PreprocessingService pps;
 
@@ -33,10 +30,6 @@ public class PDEX {
     inspect = new InspectMode(editor, pps, usage);
     rename = new Rename(editor, pps, usage);
 
-    if (SHOW_DEBUG_TREE) {
-      debugTree = new DebugTree(editor, pps);
-    }
-
     for (SketchCode code : editor.getSketch().getCode()) {
       Document document = code.getDocument();
       addDocumentListener(document);
@@ -47,28 +40,27 @@ public class PDEX {
 
 
   public void addDocumentListener(Document doc) {
-    if (doc != null) doc.addDocumentListener(sketchChangedListener);
+    if (doc != null) {
+      doc.addDocumentListener(new DocumentListener() {
+        @Override
+        public void insertUpdate(DocumentEvent e) {
+          sketchChanged();
+        }
+
+        @Override
+        public void removeUpdate(DocumentEvent e) {
+          sketchChanged();
+        }
+
+        @Override
+        public void changedUpdate(DocumentEvent e) {
+          sketchChanged();
+        }
+      });
+    }
   }
 
 
-  final DocumentListener sketchChangedListener = new DocumentListener() {
-    @Override
-    public void insertUpdate(DocumentEvent e) {
-      sketchChanged();
-    }
-
-    @Override
-    public void removeUpdate(DocumentEvent e) {
-      sketchChanged();
-    }
-
-    @Override
-    public void changedUpdate(DocumentEvent e) {
-      sketchChanged();
-    }
-  };
-
-
   public void sketchChanged() {
     errorChecker.notifySketchChanged();
     pps.notifySketchChanged();
@@ -94,9 +86,6 @@ public class PDEX {
     errorChecker.dispose();
     usage.dispose();
     rename.dispose();
-    if (debugTree != null) {
-      debugTree.dispose();
-    }
   }