Java threads problem

Question

Hi!

I have a problem with java threads:

public class MyClass{

 public void Core(){
  runTools(); //here I would like to call runTools() method
 }

 public void runTools(){

  final String run_tool ="cmd.exe /C sources.exe";

  Runnable doRun = new Runnable() {
   public void run() {
    try {
     Process tool_proc = Runtime.getRuntime().exec(run_tool);
     } 
    catch (IOException e) {
     e.printStackTrace();
    }
   }
  }; 
  Thread th = new Thread(doRun);
  th.start();

 }
}

If I do this, then I don't know why, but the thread doesn't work. Please give me some ideas to create a thread. I have already been seen lots of examples, but I should some code such as my example here. Thanks!

Answer 1

At first, if you just want to execute an external command and do not bother about its output*, then using a dedicated thread is unnecessary, since the process itself will already run in parallel to your application, so the exec() call will not really hang your programm.

Nevertheless your code looks correct to me. You should check the working directory of your application (maybe cmd.exe cannot find your sources.exe) and evaluate the output the process you start gives you, by directing the streams of tool_proc.getErrorStream() and tool_proc.getInputStream() to System.out or logging them.

EDIT: * The Java documentation states you always should read the InputStreams of your processes as failing to do so might result in filling up a system buffer, which will eventually hang the process.