Need help with threads?.. please check my approach!!

Question

Hello frnds,
I am trying to write a program.. who monitors my external tool.. please check my way of doing it.. as whenever i write programs having thread.. i end up goosy.. :(
first let me tell.. what I want from program.. I have to start an external tool.. on separate thread.. (as it takes some time).. then it takes some arguments(3 arguments).. from file.. so i read the file.. and have to run tool.. continously.. until there are arguments left.. in file.. or.. user has stopped it by pressing STOP button..
I have to put a marker in file too.. so that.. if program started again.. file is read from marker postion.. !!
Hope I make clear.. what am trying to do!!
My approach is like..
1. Have two buttons.. START and STOP on Frame..
START--> pressed
2. check marker("$" sign.. placed in beginning of file during start).. on file..
     read File from marker.. got 3 arg.. pass it to tool.. and run it.. (on separate thread).. put marker.. (for next reading)
     Step 2.. continously..
3. STOP--> pressed
     until last thread.. stops.. keep running the tool.. and when last thread stops.. stop reading any more arguments..
Question is:
1. Should i read file again and again.. ?.. or read it once after "$" sign.. store data in array.. and once stopped pressed.. read file again.. and put marker ("$" sign) at last read line..
2. how should i know when my thread has stopped.. so I start tool again??.. am totally confused.. !!
please modify my approach.. if u find anything odd..
Thanks a lot in advance
gervini

Answer 1

Hello,
I have no experience with threads or with having more than run "program" in a single java file. All my java files have the same structure. This master.java looks something like this:
---master.java---------------------------------------------------
import java.sql.*;
import...
public class Master {
public static void main(String args []) throws SQLException, IOException {
//create connection pool here
while (true) { // start loop here (each loop takes about five minutes)
// set values of variables
// select a slave process to run (from a list of slave programs)
execute selected slave program
// check for loop exit value
} // end while loop
System.out.println("Program Complete");
} catch (Exception e) {
System.out.println("Error: " + e);
} finally {
if (rSet1 != null)
try { rSet1.close(); } catch( SQLException ignore ) { /* ignored */ }
connection.close();
-------end master.java--------------------------------------------------------
This master.java program will run continuously for days or weeks, each time through the loop starting another slave process which runs for five minutes to up to an hour, which means there may be ten to twenty of these slave processes running simultaneously.
I believe threads is the best way to do this, but I don't know where to locate these slave programs: either inside the master.java program or separate slave.java files? I will need help with either method.
Your help is greatly appreciated. Thank you.
Logan