Sleep if no action in given amount of time

Question

Hello, I am trying to make my program sleep if no command is entered and come out of sleep if a command is entered. Once a command is entered it then has to go back into sleep again and so on.
This is part of a bigger program shown in a different thread - if I can get this to work I will rewrite the program so it has these properties.
At the moment it asks for input and does not display sleep every 3 seconds like it should, please give any hints on how I would make this work.
import java.util.*;
public class AIPet2
     public void sleep()
          Scanner scan = new Scanner(System.in);
          String command = scan.nextLine();
          while(command.equals(null))
               System.out.println();
               System.out.print("Sleeping");
               for(int i = 0; i < 6; i++)
                    System.out.print(".");
                    try
                         Thread.sleep(200);
                    catch(Exception e)
                         System.err.println("Caught Exception: " + e.getMessage());
               System.out.println();
               try
                    Thread.sleep(3000);
               catch(Exception e)
                    System.err.println("Caught Exception: " + e.getMessage());
               System.out.println();
     public static void main(String[] args)
          AIPet2 pet = new AIPet2();
          pet.sleep();
}

Answer 1

Ok this is what I have so far although when give input, it gives a run time error of invalidthreadstate: Please can you say what this means.
import java.util.*;
public class AIPet2
     public void input()
          while(true)
               Scanner scan = new Scanner(System.in);
               String command = scan.nextLine();
               backgroundThread.start();
     Thread backgroundThread = new Thread(new Runnable()
          public void run()
              while(true)
                    System.out.println();
                    System.out.print("Sleeping");
                    for(int i = 0; i < 6; i++)
                         System.out.print(".");
                         try
                              Thread.sleep(200);
                         catch(Exception e)
                              System.err.println("Caught Exception: " + e.getMessage());
                    System.out.println();
                    try
                         Thread.sleep(3000);
                    catch(Exception e)
                         System.err.println("Caught Exception: " + e.getMessage());
                    System.out.println();
     public static void main(String[] args)
          AIPet2 pet = new AIPet2();
          pet.input();
}