How to run multiple processes at once, while still able to type commands to system.in

[Unnar Björnsson]

I have an assignment that involves making a command provider through system.out and system.in. Im kinda stuck because my application needs to be able to open other application (notepad, cmd, etc.) and I have accomplished that but the application needs to be able to run multiple processes at once, thats where I get stuck because when I run a application like notepad my command provider which I feed commands in order to run applications, stops responding.

Basicly here�s how I do it:

private void executeRun(ArrayList<String> args)
{
try
{
program = new String[args.size()];
args.toArray(program);
Process p = Runtime.getRuntime().exec(program);
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
String temp = "";
while ((temp = input.readLine()) != null)
   System.out.println(temp);
input.close();
}
catch(Exception e){}
}

So when I type: run notepad. A notepad runs with empty txt file, but if I type: run notepad c:\myDocument.txt it opens notepad and loads the given text file.

How do I run multiple instances of f.ex notepad? I�ve tried using threads but it ain�t quite working.

[Ilja Preuss]

Can you show us your threading code that didn't work, please?

[Unnar Björnsson]

Here it goes:

public class Program implements Runnable
{
public Program(ArrayList<String> args)
{
String[] program = new String[args.size()];
args.toArray(program);
}
public void run()
{
System.out.println("Starting thread...");
try
{
Process p = Runtime.getRuntime().exec(program);
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
String temp = "";
while ((temp = input.readLine()) != null)
   System.out.println(temp);
input.close();
}
catch(IOException e){System.out.println("No can do");}
}
}

I created an instance of Program every time the executeRun command is called.

private void executeRun(ArrayList<String> args)
{
threads.add(new Thread(new Program(args)));
threads.get(threads.size()-1).run();
}

[Roy Ben Ami]

Hi,

Don't call the run method directly.

Call start() instead and it will work.

When you call run() directly it acts just like any other function. What you really need is to create a new thread and run it, and you use the start() method for that.

[Unnar Björnsson]

I figured it out, I was referring to the array program that wasn�t in the run() methods scope so I got NullPointerException. Thanks for the help though.