7Zip does not exit after processing large zip file compression

I am writing a java program on windows platform. I need to compress certain files into a zip archive. I am using ProcessBuilder to start a new 7zip process:

ProcessBuilder processBuilder = new ProcessBuilder("7Z","a",zipPath,filePath);
Process p = processBuilder.start();
p.waitFor();

The probl开发者_StackOverflowem is that the 7zip process never exits after completion. It does create the required zip file but after that just hangs in there. This means that the waitFor() call never returns and my program gets stuck. Please suggest a fix or a work around.

here is what I ended up doing.

I can't set enviroment variables so I had to set the c: path for 7zip.

    public void zipMultipleFiles (List<file> Files, String destinationFile){
        String zipApplication = "\"C:\\Program Files\7Zip\7zip.exe\" a -t7z"; 
        String CommandToZip = zipApplication + " ";    
        for (File file : files){
           CommandToZip = CommandToZip + "\"" + file.getAbsolutePath() + "\" ";
        }
        CommandToZip = CommandToZip + " -mmt -mx5 -aoa";
        runCommand(CommandToZip);
    }

    public void runCommand(String commandToRun) throws RuntimeException{
        Process p = null;
        try{
            p = Runtime.getRuntime().exec(commandToRun);
            String response = convertStreamToStr(p.getInputStream());
            p.waitFor();
        } catch(Exception e){
            throw new RuntimeException("Illegal Command ZippingFile");
        } finally {
            if(p = null){
                throw new RuntimeException("Illegal Command Zipping File");
            }
            if (p.exitValue() != 0){
                throw new Runtime("Failed to Zip File - unknown error");
            }
        }
    }

The convert to string function can be found here which is what I used as a reference. http://singztechmusings.wordpress.com/2011/06/21/getting-started-with-javas-processbuilder-a-sample-utility-class-to-interact-with-linux-from-java-program/