MLFQueue.java

import java.util.concurrent.*;
import java.util.*;

public final class MLFQueue {

  private  int MAX_NUM_OF_PROCESSES = 20;
  private int queue1Quantum = 8, queue2Quantum = 16, contextSwitchTime=2;

  private int lastProcessQueue;
  private Object[] queues = new Object[3];

  public MLFQueue(int q0,int q1, int ctxt, int dgr){
    queue1Quantum = q0;
    queue2Quantum = q1;
    contextSwitchTime = ctxt;
    MAX_NUM_OF_PROCESSES = dgr;
    queues[0] = new RRQueue(queue1Quantum,contextSwitchTime);
    queues[1] = new RRQueue(queue2Quantum,contextSwitchTime);
    queues[2] = new ArrayList();
  }
    public MLFQueue() {
    this(8,16,2,20);
    }

  // Each new process should be added to the first RRQueue
  // If the queues are already full (20 processes), then this method should block unti there's some space for it.
  public void add(Object o){
    ((RRQueue)queues[0]).add(o);
  }

  public void add(Object o, int queueNum){
    if(queueNum == 2)
      ((ArrayList)queues[queueNum]).add(o);
    else
      ((RRQueue)queues[queueNum]).add(o);
  }

  public int getNumOfElements(){
    return (((RRQueue)queues[0]).getSize() + ((RRQueue)queues[1]).getSize() + ((ArrayList)queues[2]).size());
  }

  // Queue 0 processes will return first
  // If Queue 0 doesn't contain processes, Queue 1 processes will return
  // If Queue 1 also doesn't contain processes, Queue 2 processes will return
  // Else it will return null
  public Object poll(){
    if(((RRQueue)queues[0]).getSize() != 0){
      lastProcessQueue = 0;
      return ((RRQueue)queues[0]).poll();
    }
    else if(((RRQueue)queues[1]).getSize() != 0){
      lastProcessQueue = 1;
      return ((RRQueue)queues[1]).poll();
    }
    else if(((ArrayList)queues[2]).size() != 0){
      lastProcessQueue = 2;
      Process p = (Process)((ArrayList)queues[2]).get(0);
      ((ArrayList)queues[2]).remove(0);
      return p;
    }
    return null;
  }

  public int getLastProcessQueue()
  {
    return lastProcessQueue;
  }

  public int getQueue1Quantum(){
    return queue1Quantum;
  }

  public int getQueue2Quantum(){
    return queue2Quantum;
  }

  public void removeFromFCFS(Object o){
    ((ArrayList)queues[2]).remove(o);
  }

}

RRQueue.java

import java.util.*;

public final class RRQueue {

  private ArrayList queue = new ArrayList();
  private int quantum;
  private int contextSwitchingTime;

  public RRQueue(int quantum, int context) {
  this.quantum = quantum;
  this.contextSwitchingTime = context;
  }

  public int getQuantum(){
    return quantum;
  }

  public int getContextSwitchingTime(){
    return contextSwitchingTime;
  }

  public void add(Object o){
    queue.add(o);
  }

  public Object poll(){
    Object o = queue.get(0);
    queue.remove(0);
    return o;
  }

  public void remove(int index){
    queue.remove(index);
  }

  public int getSize(){
    return queue.size();
  }
}