diff -r cfde9737131e -r 170e486632d9 src/share/classes/com/sun/tools/javac/util/ListBuffer.java
--- a/src/share/classes/com/sun/tools/javac/util/ListBuffer.java	Tue Dec 11 15:05:55 2012 -0800
+++ b/src/share/classes/com/sun/tools/javac/util/ListBuffer.java	Wed Dec 12 20:26:56 2012 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -52,19 +52,20 @@
 
     /** The list of elements of this buffer.
      */
-    public List<A> elems;
+    private List<A> elems;
 
-    /** A pointer pointing to the last, sentinel element of `elems'.
+    /** A pointer pointing to the last element of 'elems' containing data,
+     *  or null if the list is empty.
      */
-    public List<A> last;
+    private List<A> last;
 
     /** The number of element in this buffer.
      */
-    public int count;
+    private int count;
 
     /** Has a list been created from this buffer yet?
      */
-    public boolean shared;
+    private boolean shared;
 
     /** Create a new initially empty list buffer.
      */
@@ -73,8 +74,8 @@
     }
 
     public final void clear() {
-        this.elems = new List<A>(null,null);
-        this.last = this.elems;
+        this.elems = List.nil();
+        this.last = null;
         count = 0;
         shared = false;
     }
@@ -103,22 +104,23 @@
     /** Copy list and sets last.
      */
     private void copy() {
-        List<A> p = elems = new List<A>(elems.head, elems.tail);
-        while (true) {
-            List<A> tail = p.tail;
-            if (tail == null) break;
-            tail = new List<A>(tail.head, tail.tail);
-            p.setTail(tail);
-            p = tail;
+        if (elems.nonEmpty()) {
+            List<A> orig = elems;
+
+            elems = last = List.<A>of(orig.head);
+
+            while ((orig = orig.tail).nonEmpty()) {
+                last.tail = List.<A>of(orig.head);
+                last = last.tail;
+            }
         }
-        last = p;
-        shared = false;
     }
 
     /** Prepend an element to buffer.
      */
     public ListBuffer<A> prepend(A x) {
         elems = elems.prepend(x);
+        if (last == null) last = elems;
         count++;
         return this;
     }
@@ -128,9 +130,13 @@
     public ListBuffer<A> append(A x) {
         x.getClass(); // null check
         if (shared) copy();
-        last.head = x;
-        last.setTail(new List<A>(null,null));
-        last = last.tail;
+        List<A> newLast = List.<A>of(x);
+        if (last != null) {
+            last.tail = newLast;
+            last = newLast;
+        } else {
+            elems = last = newLast;
+        }
         count++;
         return this;
     }
@@ -192,8 +198,9 @@
      */
     public A next() {
         A x = elems.head;
-        if (elems != last) {
+        if (!elems.isEmpty()) {
             elems = elems.tail;
+            if (elems.isEmpty()) last = null;
             count--;
         }
         return x;
@@ -205,10 +212,10 @@
         return new Iterator<A>() {
             List<A> elems = ListBuffer.this.elems;
             public boolean hasNext() {
-                return elems != last;
+                return !elems.isEmpty();
             }
             public A next() {
-                if (elems == last)
+                if (elems.isEmpty())
                     throw new NoSuchElementException();
                 A elem = elems.head;
                 elems = elems.tail;
@@ -263,4 +270,8 @@
     public A peek() {
         return first();
     }
+
+    public A last() {
+        return last != null ? last.head : null;
+    }
 }