--- a/langtools/src/share/classes/com/sun/tools/javac/main/JavaCompiler.java	Tue Sep 07 15:49:48 2010 -0700
+++ b/langtools/src/share/classes/com/sun/tools/javac/main/JavaCompiler.java	Thu Sep 09 09:42:45 2010 +0530
@@ -872,8 +872,13 @@
 
         //parse all files
         ListBuffer<JCCompilationUnit> trees = lb();
-        for (JavaFileObject fileObject : fileObjects)
-            trees.append(parse(fileObject));
+        Set<JavaFileObject> filesSoFar = new HashSet<JavaFileObject>();
+        for (JavaFileObject fileObject : fileObjects) {
+            if (!filesSoFar.contains(fileObject)) {
+                filesSoFar.add(fileObject);
+                trees.append(parse(fileObject));
+            }
+        }
         return trees.toList();
     }