what are these numbers? The factor the new version is faster? Well for the empty string that may make sense, but that is not really a relevant case I think. The HTML page is more interesting and more in the area I expected.... but the 64k string... factor 200... that is unexpected.
trunk is supposed to support 1.5 only yes. The retro build can create a 1.4 compatible version for StringBuilder, so the usage of that class is no problem. We are also step-by-step replacing all usages of StringBuffer with StringBuilder already