diff -r 874788e4c176 -r 3adeeb9c080e hotspot/src/share/vm/runtime/arguments.cpp
--- a/hotspot/src/share/vm/runtime/arguments.cpp	Mon Jun 28 12:03:05 2010 -0400
+++ b/hotspot/src/share/vm/runtime/arguments.cpp	Wed Jun 30 11:52:10 2010 -0400
@@ -1508,6 +1508,9 @@
   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) {