execute an external command in java

Question

Is there a way to execute a command in java that doesn't suffer from the startup overhead (slowness) of using ProcessBuilder?

More detail: I am using im4java which is a java library that internally uses ProcessBuilder to execute imagemagick's programs. It is slow. I have created a small unit test that shows that ProcessBuilder (not im4java) is the problem. The slowness is the startup overhead of using ProcessBuilder. I have found posts around the internet saying processbuider has overhead so its not just me saying it does.

List<String> commands = new ArrayList<String>();
commands.add("C:\\PROGRA~2\\ImageMagick-6.6.4-Q16\\convert.exe");
commands.add("dog.jpg");
commands.add("output.jpg");
ProcessBuilder processBuilder = new ProcessBuilder(commands);
Process start = processBuilder.start();
start.waitFor();

Answer 1

Runtime.getRuntime().exec(...)  

can be used to run an external command. You can turn your List into a command array or a string to pass to exec().

Answer 2

This is not recommended, but you could write a JNI library to do the same thing that ProcessBuilder is doing. Perhaps yours would be faster, but I wouldn't count on it, plus you would lose cross-platform compatibility.

How slow are we talking here? I'm using ProcessBuilder myself for running Git commands (haven't had a chance to look into JGit yet), and it seems snappy enough. You may have better luck on Linux, as the overhead may actually be in Windows heavyweight process creation.