--- old/src/share/classes/jdk/internal/org/objectweb/asm/ClassWriter.java	Fri May 30 13:40:19 2014
+++ new/src/share/classes/jdk/internal/org/objectweb/asm/ClassWriter.java	Fri May 30 13:40:19 2014
@@ -785,11 +785,29 @@
         if (innerClasses == null) {
             innerClasses = new ByteVector();
         }
-        ++innerClassesCount;
-        innerClasses.putShort(name == null ? 0 : newClass(name));
-        innerClasses.putShort(outerName == null ? 0 : newClass(outerName));
-        innerClasses.putShort(innerName == null ? 0 : newUTF8(innerName));
-        innerClasses.putShort(access);
+        // Sec. 4.7.6 of the JVMS states "Every CONSTANT_Class_info entry in the
+        // constant_pool table which represents a class or interface C that is
+        // not a package member must have exactly one corresponding entry in the
+        // classes array". To avoid duplicates we keep track in the intVal field
+        // of the Item of each CONSTANT_Class_info entry C whether an inner
+        // class entry has already been added for C (this field is unused for
+        // class entries, and changing its value does not change the hashcode
+        // and equality tests). If so we store the index of this inner class
+        // entry (plus one) in intVal. This hack allows duplicate detection in
+        // O(1) time.
+        Item nameItem = newClassItem(name);
+        if (nameItem.intVal == 0) {
+            ++innerClassesCount;
+            innerClasses.putShort(nameItem.index);
+            innerClasses.putShort(outerName == null ? 0 : newClass(outerName));
+            innerClasses.putShort(innerName == null ? 0 : newUTF8(innerName));
+            innerClasses.putShort(access);
+            nameItem.intVal = innerClassesCount;
+        } else {
+            // Compare the inner classes entry nameItem.intVal - 1 with the
+            // arguments of this method and throw an exception if there is a
+            // difference?
+        }
     }
 
     @Override