Question

When I try to run(use) the last method, it start running and never stops. Also When I try to print out aJob the element does not print out correctly. It comes out with odd letters. I am posting the whole class because I am guessing that I am making a mistake somewhere else apart from runJod and runAll methods. could anyone tell me what I need to do to fix this please?

import java.util.ArrayList;

/**
*/

public class JobQueue

{
private ArrayListmyJobInQueue; //a list of job to be done

private ArrayList<Job>myFinishedJobs;// a list of compleated job

private int myJobDuration; //duration if one job

private int myTimeLeft;//total time left 
/**
 * Constructor for objects of class JobQueue
 */
 public JobQueue()
{
  myJobInQueue = new ArrayList<Job>();
  myFinishedJobs = new ArrayList<Job>();
  myJobDuration =0; 
  myTimeLeft=0;  
}

/**
 * Return the list of jobs that have not been completed (including the current job).
 */
 public ArrayList<Job> getPendingJobs()
 {
  return myJobInQueue;  
 }

/**
 * Return the list of jobs that have been completed.
 */
 public ArrayList<Job> getCometedJobs()
 {
  return myFinishedJobs;
 } 

/**
 * Return the job at the front of the pending queue, or null if the queue is empty.
 */
 public Job getCurrentJob()
 {
   if(myJobInQueue!=null)
   { 
    Job FirstJobInTheQueue = myJobInQueue.get(0);   
    return FirstJobInTheQueue;
   }
   else
   {
    return null;
   }

 } 

/**
 * Return the amount of time left on the clock (as an integer)
 */
 public int getTimeLeft()//Ok
 {
   return myTimeLeft; 
 }

/**
 * Return the total duration of all the pending jobs(as an integer).
 */

 public int getTotalDuration()
 {
   int myTimeLeft= 0;
   for(int i = 0; i<myJobInQueue.size();i++)
   {
       int num = myJobInQueue.getDuration(i); //I think this line is wrong. 
       myTimeLeft = myTimeLeft + num ;
   }
   return myTimeLeft;
 }

/**
 * Add a Job to the end of the Queue
 */ 
 public void addJob(Job job)
 {   
    if(job!=null)
    {
      myJobInQueue.add(job);
    }
 }

/**
  * Add the specified number of seconds to the clock.
  */
 public void addTime(int seconds)
 {
    if(seconds>0)
    {
      myTimeLeft = myTimeLeft  + seconds;
    }
 }

 /**
  * Run the first job on the queue if there is enough time on the clock and the job queue list is not empty.
  * And move the job to the finished jobs list.
  */

 public void runAJob(){
   if(!myJobInQueue.isEmpty())
   {
        myJobDuration = myJobInQueue.get(0).getDuration();
        if (myJobDuration < myTimeLeft)
        {
            myTimeLeft = myTimeLeft - myJobDuration;
            myFinishedJobs.add(myJobInQueue.get(0));
            System.out.println("A job is running: " + myJobInQueue.get(0).getName());
            myJobInQueue.remove(0);
        }
        else 
        {
            System.out.println("Not enogth running time left, please add time on the clock.");             
        }
   }
   else 
   {
     System.out.println("No pending job on the list.");
   }
}

/**
  * Run all the jobs on the queue in order until it runs out of time.
 */   


public void runAll()
{
  for(int i = 0; myTimeLeft > 0 && myTimeLeft > myJobDuration;i++);
  {
    runJob();

  }
   System.out.println("Job can not be run, not enough time left." );   
}

}

Answer 1

Based on your comment, the line System.out.println("Ajob is running"+ myJobInQueue.get(0)); is printing out the object reference for the Job returned by myJobInQueue.get(0). In order for that line to print out meaningful information, just make sure Job has a toString method that returns a String that describes the object.

I think your second problem is caused by the myTimeLeft variable dropping below myJobDuration, but not below 0. I don’t see where you decrement myTimeLeft when it’s in this window.

Side Note: Do all jobs have the same duration? If not, then you should probably be using the duration for the next Job instead of a global myJobDuration variable.