Message1575

Adding string to another like this
for line in lines:
    xml = xml + line
has extremely low performance in comparison with CPython

Simple testcase is attached. 
generator.py generates file of given size (first argument) with approximate line count (second argument)

test.py reads file from generated file, collecting all lines in one, and prints time of this operation

For input:
python generator.py 21 90000
(that is 2M file with approx. 90K lines)

python takes 1882 ms
jython fails to finish in more than 10 minutes