COMP2240-Assignment1/FCFS.java

import java.util.LinkedList;

/**
 * First Come First Serve Algorithm
 */
public class FCFS {

    private int timeStep = 0;
    private int disp;
    private int timeLastChecked = -1;

    private static LinkedList<Process> processListFromFile;   //Original List of processes from the the file
    private LinkedList<Process> waitingQueue = new LinkedList<>();  //Processes officially added to the waiting queue.
    private LinkedList<Process> newProcesses = new LinkedList<>();  //Processes that have arrived after each time point.
    //Constructors

    public FCFS(int dispInput, LinkedList<Process> processListInput)
    {
        disp = dispInput;
        processListFromFile = processListInput;
    }


    private void checkForArrivals()
    {
        for(int i = 0; i< processListFromFile.size(); i++)
        {
            if((processListFromFile.get(i).getArrive()<=timeStep) && (processListFromFile.get(i).getArrive() > timeLastChecked))
            {
                newProcesses.add(processListFromFile.get(i));
            }
        }

        timeLastChecked = timeStep;

        //do any tie breaking by sorting the new processes based on name
        boolean swap = false;
        do
        {
            swap = false;
            for(int i = 0; i< newProcesses.size()-1; i++)
            {          
                if(Integer.parseInt(newProcesses.get(i).getId().substring(1))>Integer.parseInt(newProcesses.get(i+1).getId().substring(1)))
                {
                    Process temp = newProcesses.get(i);
                    newProcesses.remove(i);
                    newProcesses.add(i+1, temp);
                    swap = true;
                }
            }
        }while(swap);

        //Move the newly arrived (and organised) processes to the queue.
        for(int i =0; i < newProcesses.size(); i++)
        {
            waitingQueue.add(newProcesses.get(i));
        }
        
        newProcesses.clear();
    }

    public void runDispatch()
    {
        System.out.println("FCFS:");
        int processesFinished = 0;
        boolean startNew = true;
        //timeStep++;
        
        do
         {
            if(startNew)
            {
                timeStep = timeStep+disp;
                startNew = false; 
            }
            else
            {
                ;
            }
            
            checkForArrivals();
             
            if(waitingQueue.size()>0)
            {
                if(waitingQueue.getFirst().isDone())
                {
                    waitingQueue.removeFirst();
                    processesFinished++;
                    startNew = true;
                }
                else
                {
                    runProcessTick(waitingQueue.getFirst());
                }
            }
            
         }while(processesFinished!=processListFromFile.size());      
    }

    private void runProcessTick(Process input)
    {   
        input.saveStartTime(timeStep);
        
        timeStep++;

        input.runForOneTick();

        if(input.isDone())
        {
            input.saveEndTime(timeStep);
            input.saveTurnTime();
            input.saveWaitTime();
        }       
    }    

    public void printResults()
    {
        for (int i = 0; i < processListFromFile.size(); i++)
        {
            System.out.println("T"+processListFromFile.get(i).getStartTime()+": "+processListFromFile.get(i).getId());
        }
        
        System.out.println("\nProcess \tTurnaround Time \tWaiting Time");
        for (int i = 0; i < processListFromFile.size(); i++)
        {
            System.out.print(processListFromFile.get(i).getId()+"\t\t");
            System.out.print(processListFromFile.get(i).getTurnTime()+"\t\t\t");
            System.out.print(processListFromFile.get(i).getWaitTime()+"\n");
        }
    }
}