Further modifying the Robot program to take the input from properties file in a specific format:

[1] TestRobot.java

import java.awt.AWTException;

import java.awt.Robot;

import java.io.FileInputStream;

import java.io.IOException;

import java.util.Date;

import java.util.Properties;

import java.util.regex.Pattern;

import javax.swing.KeyStroke;

/*

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 * and open the template in the editor.

 */

/**

 *

 * @author PD

 * This program will execute set of mouse key events repeatedly after a sleep.

 * Keys input will be taken from the properties file in format: [PRESS|RELEASE]::[PRESS|RELEASE]:

 * E.g. PRESS:A:RELEASE:A

 * Press denotes Keyboard KeyPress event where as RELEASE dentoes KeyRelease event.

 * Above example will press and release keyboard key A after every value mentioned in properties file [default is 1 min].

 */

public class TestRobot {

private static enum Key{PRESS, RELEASE};

    private static final int DEFAULT_SLEEP_TIME_IN_MILLISEC = 10000; // 60000 milliseconds = 1 min

    public static void main(String[] args) throws AWTException, IOException 

    {

    long startTime = new Date().getTime();

        Robot r = new Robot();

        Properties p = new Properties();

        int sleepTime = 0;

        int endTime = 0;

        String[] keyArray = null;

        try {

            p.load(new FileInputStream("live.properties"));

            sleepTime = Integer.parseInt(p.getProperty("wakeup.time"));

            System.out.println("sleepTime = " + sleepTime);

            if(sleepTime == 0)

            sleepTime = DEFAULT_SLEEP_TIME_IN_MILLISEC;

            endTime = Integer.parseInt(p.getProperty("execution.time"));

            System.out.println("Execution Time : " + endTime);

            String keys = p.getProperty("keys");

            if(keys != null) {

            if(!Pattern.matches("^((PRESS|RELEASE):\\w+:)+(PRESS|RELEASE):\\w+$", keys))

            throw new Exception("INVALID keys. Expecting value for keys in properties file in format '[PRESS|RELEASE]::[PRESS|RELEASE]:' i.e. PRESS or RELEASE must followed by a key.\nE.g. for ALT+S provide keys = PRESS:ALT:PRESS:S:RELEASE:S:RELEASE:ALT");

            keyArray = keys.split(":");

             if(keyArray == null)

            throw new Exception("INVALID keys. Expecting value for keys in properties file in format '[PRESS|RELEASE]::[PRESS|RELEASE]:' i.e. PRESS or RELEASE must followed by a key.\nE.g. for ALT+S provide keys = PRESS:ALT:PRESS:S:RELEASE:S:RELEASE:ALT");

            }

          

       while(true) {

           try {

            Thread.sleep(sleepTime);

           } catch (InterruptedException e1) {

               break;

           }

           for (int i = 0; i < keyArray.length; i+=2) {

            Key key = Key.valueOf(keyArray[i]);

            switch (key) {

case PRESS:

r.keyPress(KeyStroke.getKeyStroke(keyArray[i+1]).getKeyCode());

break;

case RELEASE:

r.keyRelease(KeyStroke.getKeyStroke(keyArray[i+1]).getKeyCode());

break;

default:

throw new Exception("INVALID keys. Expecting value for keys in properties file in format '[PRESS|RELEASE]::[PRESS|RELEASE]:' i.e. PRESS or RELEASE must followed by a key.\nE.g. for ALT+S provide keys = PRESS:ALT:PRESS:S:RELEASE:S:RELEASE:ALT");

}

}

            if(endTime <= 0 && (startTime + endTime) < new Date().getTime()) {

            System.exit(0);

           }

       }

    } catch (Exception e) {

            e.printStackTrace();

            System.exit(0);

    }

        

    }

}

[2] live.properties

# Time is in miliseconds & execution.time <= 0 is infinite

execution.time = 1200000

wakeup.time = 240000

# keys format '[PRESS|RELEASE]:' E.g. for ALT+S provide keys = PRESS:ALT:PRESS:S:RELEASE:S:RELEASE:ALT

keys = PRESS:ALT:PRESS:TAB:RELEASE:TAB:PRESS:SHIFT:PRESS:TAB:RELEASE:TAB:RELEASE:SHIFT:RELEASE:ALT

Note:
With above values of properties file, program will execute keys repetitively after every 4 min for total 20 min.   keys are "ALT+TAB" followed by "ALT+SHIFT+TAB".