diff -r c046f8e9c52b -r ba0c3b725081 hotspot/src/share/vm/runtime/arguments.cpp
--- a/hotspot/src/share/vm/runtime/arguments.cpp	Mon Jun 28 14:54:39 2010 -0700
+++ b/hotspot/src/share/vm/runtime/arguments.cpp	Tue Jun 29 10:34:00 2010 -0700
@@ -1513,6 +1513,9 @@
   if (AggressiveOpts && FLAG_IS_DEFAULT(BiasedLockingStartupDelay)) {
     FLAG_SET_DEFAULT(BiasedLockingStartupDelay, 500);
   }
+  if (AggressiveOpts && FLAG_IS_DEFAULT(OptimizeStringConcat)) {
+    FLAG_SET_DEFAULT(OptimizeStringConcat, true);
+  }
 #endif
 
   if (AggressiveOpts) {