Unjaring a .jar file in Objective-C

I was wondering if it was possible to extract the contents of a .jar file into a different directory, then add some files to that directory, and then compress the directory back into a .jar file, with the additions. A way of extracting the jar file i found was to use NSTask to execute the terminal command of jar xf (location of jar file) . This worked, but it halted the UI of the program permanently (without crashing it), and unarchived the contents into the directory that the application was stored in, which was a slight mess to clean up. Is there another way of doing this, or am I using NSTask incorrectly? Here is the code I am using:

//Unarchive the jar

[self runCommandWithBase:@"/usr/bin/jar" arguments:[NSArray arrayWithObjects:@"xf", jarLocation, nil]];

and

- (NSString *)runCommandWithBase:(NSString *)base arguments:(NSArray *)arguments {

//Create the task

NSTask *task = [[NSTask alloc] init];



//Setup the task

[task setLaunchPath:base];

[task setArguments:arguments];

[task setStandardInput:[NSPipe pipe]];

[task setStandardOutput:[NSPipe pipe]];



//Set file handle

NSFileHandle *file = [[NSPipe pipe] fileHandleForReading];



//Run the command

[task launch];



//Return

NSData *returnData = [file readDataToEndOfFile];

return [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];}

Is there maybe a way to include a java application in Xcode that will unarchive the files, add the other files, and then re-compress it? Then execute the java application with NSTask ?

Thanks in Advance,

Ben