Question

When I run my application and scan for an IP it freezes for some reason. Also, I am not sure if the Yum method is exiting once it run the command, or if it lives forever. My target was to make something like $ ./inLinuxRunMe &, where it runs in the background, and when the job is done, it kills itself.

I don’t think that my Yum method is doing this, because it freezes when I start heavy loads such as playing video’s etc.

public class MyShell
{
    public static String whatIsMyIP = null;

    public static void main(String args[])
    {
      t = new javax.swing.Timer(10000, new ActionListener() 
      {
        public void actionPerformed(ActionEvent ae) 
        {
        /* Scanner: if the ip change, show the new on too. */
        whatIsMyIP = MyShell.Yum("ifconfig eth0 | grep inet").toLowerCase());           
            /* Some logical conditions ... such as if ran then dont run, run once etc..*/ 
            bootMe();
         }
      });
      t.start();

      /* Launch: Main application server, runs forever as server */
      // MyShell.Yum("java -cp myjar.jar launch.MainApplicationAsServer");
    }

    /* Boot loader */
    public static void bootMe() throws IOException
    {
      MyShell.Yum("java -cp myjar.jar launch.MainApplicationAsServer");
    }

    /* Question: How to optimize it? So that, 
             it execute the shell command and quite*/
    public static String Yum(String cmds)
    {
        String value = "";
        try 
        {
          String cmd[] = {"/bin/sh", "-c", cmds };       
          Process p=Runtime.getRuntime().exec(cmd);       
          BufferedReader reader=new BufferedReader(
                                                                            new InputStreamReader(p.getInputStream())); 
          String line=reader.readLine(); 

          while(line!=null) 
          { 
            value += line ;
            line=reader.readLine(); 
          } 
          p.waitFor(); 

        } catch(IOException e1) {
        } catch(InterruptedException e2) { 
        }
        return value;
    }
}

Answer 1

From the Java API:

Constructor Summary
Timer(int delay, ActionListener listener)
      Creates a Timer that will notify its listeners every `delay` milliseconds.

So it repeats every 10 seconds. You need to tell it not to repeat:

public void setRepeats(boolean flag)

    If flag is false, instructs the Timer to send only one action event to its listeners.

    Parameters:
        flag - specify false to make the timer stop after sending its first action event

So:

t = new javax.swing.Timer(10000, new ActionListener() {...});
t.setRepeats(false);
t.start();