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Implementation for Round Robin Algorithm in Java with tests
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‎src/main/java/com/others/RoundRobin.java

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package src.main.java.com.others;
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import java.util.ArrayList;
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/**
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* This class implements the Round Robin Algorithm which is an cpu scheduling algorithm.
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*
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* @author George Giannios
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*/
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public class RoundRobin {
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/**
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* This method calculates the waiting time for all processes
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*
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* @param burstTime an array with burst time for all processes
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* @param quantum the quantum quantity
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*
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* @return an array with waiting time for all processes
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*/
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public int[] calcWaitingTime(int[] burstTime, int quantum)
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{
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int n= burstTime.length;
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//create a copy of burstTime table to executeTime table
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int[] executeTIme= new int [n];
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for (int i=0;i<n;i++)
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executeTIme[i]=burstTime[i];
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//initialize the waiting time table and set all waiting times equal to zero
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int[] waitingTime= new int [n];
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for (int i=0;i<n;i++)
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waitingTime[i]=0;
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//initialize an array list to emulate the queue of ready processes
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ArrayList<Integer> readyQueue = new ArrayList<>();
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for(int i=0;i<n;i++)
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readyQueue.add(i);
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//the total time that processes need to be finished
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int time=0;
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int i=0;
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//calculate waiting times while there are uncompleted processes
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while (!readyQueue.isEmpty())
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{
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//check if a process has finished
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if (executeTIme[i]>=0) {
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if (executeTIme[i] - quantum > 0) {
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//add time that have been passed
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time += quantum;
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//this is the remaining burst time for the process i
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executeTIme[i] -= quantum;
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} else if (executeTIme[i] - quantum == 0) {
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//add time that have been passed
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time += quantum;
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//calculate the total waiting time
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waitingTime[i] = time - burstTime[i];
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//mark the process as finished
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executeTIme[i] = -1;
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//remove the process that have finished by shrinking queue's length
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readyQueue.remove(readyQueue.size()-1);
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} else {
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//add time that have been passed
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time += executeTIme[i];
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//calculate the total waiting time
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waitingTime[i] = time - burstTime[i];
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//mark the process as finished
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executeTIme[i] = -1;
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//remove the process that have finished by shrinking queue's length
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readyQueue.remove(readyQueue.size()-1);
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}
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}
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i++;
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if(i>=n) i=0;
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}
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return waitingTime;
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}
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/**
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* This method calculates turn around time for all processes
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*
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* @param burstTime an array with burst time for all processes
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* @param waitingTime an array with waiting time for all processes
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*
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* @return an array with turnaround time for all processes
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*/
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public int[] calcTurnAroundTime(int[] burstTime, int[] waitingTime)
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{
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int n= burstTime.length;
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//initialize the turnaround time table
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int[] turnAroundTime= new int [n];
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//calculate turnaround time for each process (T.T= W.T + B.T)
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for (int i=0; i<n;i++)
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turnAroundTime[i]=waitingTime[i]+burstTime[i];
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//return the turnaround time table
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return turnAroundTime;
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}
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/**
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* This method prints the results and calculates the average waiting and turnaround times
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*
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* @param burstTime an array with burst time for all processes
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* @param quantum the quantum quantity
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*/
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void printAvgTimes(int[] burstTime, int quantum)
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{
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int n = burstTime.length;
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int totalWaitingTime = 0;
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int totalTurnAroundTime = 0;
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// Find waiting time of all processes
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int[] waitingTime = calcWaitingTime(burstTime, quantum);
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// Find turn around time for all processes
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int[] turnAroundTime = calcTurnAroundTime(burstTime, waitingTime);
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// Display processes along with all details
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System.out.println("Process " + " Burst Time " +
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" Waiting Time " + " Turnaround Time");
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System.out.println("======= ========== ============ ===============");
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// Calculate total waiting time and total turn around time
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for (int i = 0; i < n; i++) {
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totalWaitingTime += waitingTime[i];
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totalTurnAroundTime += turnAroundTime[i];
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System.out.println(i + "\t\t " + burstTime[i] +"\t\t\t " +
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waitingTime[i] +"\t\t\t " + turnAroundTime[i]);
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}
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System.out.println("\nAverage waiting time = " +
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(float)totalWaitingTime / (float)n);
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System.out.println("Average turnaround time = " +
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(float)totalTurnAroundTime / (float)n);
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}
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}
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‎src/test/java/com/others/RoundRobinTest.java

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package src.test.java.com.others;
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import org.junit.Assert;
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import org.junit.Test;
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import src.main.java.com.others.RoundRobin;
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public class RoundRobinTest {
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private final int[] burstTime = {5, 15, 4, 3};
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private final RoundRobin roundRobin = new RoundRobin();
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@Test
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public void testWaitingTime(){
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int[] expectedTime = {9,12,14,9};
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int[] realtime= roundRobin.calcWaitingTime(burstTime,3);
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Assert.assertArrayEquals(realtime, expectedTime);
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}
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@Test
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public void testTurnAroundTIme(){
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int[] expectedTIme={14,27,18,12};
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int[] waitingTime = {9,12,14,9};
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int[] realTime= roundRobin.calcTurnAroundTime(burstTime,waitingTime);
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Assert.assertArrayEquals(realTime,expectedTIme);
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}
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}

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