Compress exe/dll/jar Script

What you are looking for is UPX for your exe's and your dll's. JAR files are just zip files (only the extension changes). Therefore, you can use 7-Zip for that. Just un zip, and re-zip using higher compression. Once you are finished change the extension from zip (or 7z) to jar.
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Marge: Homer, the plant called. They said if you don't show up tomorrow don't bother showing up on Monday.
Homer: Woo-hoo. Four-day weekend.

On asking John about that if he ever emails me back
(I have a sneaking suspicion that he's on holidays again)
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Ryan McCue
Person 1: Oh my god. You will never believe what just happened.
Person 2: What?
Person 1: I can't remember, I've forgotten.

You can use this simple batch file for the .JAR file(s):

@echo off

rem J2Z.BAT
rem Quick'n dirty solution to repack a JAR file with 7zip.
rem The one and only parameter is the JAR file name without extension.
rem The JAR file itself will be overwritten with the new ZIP file.
rem You can use with the following command line or batch:
rem for %%a in (*.jar) do call j2z %%~na
rem to compress all .JAR files in a directory.

rem 7zip executable existense check (set up with your path)
set _7zp=7z.exe
if not exist %_7zp% goto no7zp

rem JAR file existense check
set _jar=%1.jar
if not exist %_jar% goto nojar

rem temp directory existense check
set _tmp=%temp%
if not exist %_tmp% goto notmp

rem we shall need a work directory
if exist %_tmp%\%1 rd /q /s %_tmp%\%1
md %_tmp%\%1

rem extracting JAR file to work directory
%_7zp% x %_jar% -o%_tmp%\%1\

rem repacking JAR file with 7zip
%_7zp% a -mx=9 -r -tzip %_jar% %_tmp%\%1\*.*

rem purge work directory
rd /q /s %_tmp%\%1

rem finished for now
goto end

rem no 7zip executable found
:no7zp
echo 7zip executable (%_7zp%) not found.
pause
goto end

rem no JAR file found
:nojar
echo JAR file (%_jar%) not found.
pause
goto end

rem no temp directory found
:notemp
echo Temp directory (%_tmp%) not found.
pause
goto end

rem this is the end, my friend
:end
set _7zp=
set _jar=
set _tmp=

For .EXE and .DLL files, you can use the following command:

upx *.exe *.dll

Some official recursive stuff would be a lot more more fun, of course :).

I'm re-doing all my scripts and I found a typo in the original JAR recompression script posted to this thread and the one I did later that uses recursion.

This line:

if not exist %_tmp% goto notmp

Needs to be changed to:

if not exist %_tmp% goto notemp