From 72efcaa5647f25a29b625ccf7b4c9e762fa951a2 Mon Sep 17 00:00:00 2001
From: geogiadim <gia1914g@gmail.com>
Date: Wed, 16 Sep 2020 19:19:50 +0300
Subject: [PATCH] Implementation for Round Robin Algorithm in Java with tests

---
 src/main/java/com/others/RoundRobin.java     | 141 +++++++++++++++++++
 src/test/java/com/others/RoundRobinTest.java |  26 ++++
 2 files changed, 167 insertions(+)
 create mode 100644 src/main/java/com/others/RoundRobin.java
 create mode 100644 src/test/java/com/others/RoundRobinTest.java

diff --git a/src/main/java/com/others/RoundRobin.java b/src/main/java/com/others/RoundRobin.java
new file mode 100644
index 00000000..cb17853d
--- /dev/null
+++ b/src/main/java/com/others/RoundRobin.java
@@ -0,0 +1,141 @@
+package src.main.java.com.others;
+
+import java.util.ArrayList;
+
+/**
+ * This class implements the Round Robin Algorithm which is an cpu scheduling algorithm.
+ *
+ * @author George Giannios
+ */
+public class RoundRobin {
+    /**
+     * This method calculates the waiting time for all processes
+     *
+     * @param burstTime an array with burst time for all processes
+     * @param quantum the quantum quantity
+     *
+     * @return an array with waiting time for all processes
+     */
+    public int[] calcWaitingTime(int[] burstTime, int quantum)
+    {
+        int n= burstTime.length;
+        //create a copy of burstTime table to executeTime table
+        int[] executeTIme= new int [n];
+        for (int i=0;i<n;i++)
+            executeTIme[i]=burstTime[i];
+
+        //initialize the waiting time table and set all waiting times equal to zero
+        int[] waitingTime= new int [n];
+        for (int i=0;i<n;i++)
+            waitingTime[i]=0;
+
+        //initialize an array list to emulate the queue of ready processes
+        ArrayList<Integer> readyQueue = new ArrayList<>();
+        for(int i=0;i<n;i++)
+            readyQueue.add(i);
+
+        //the total time that processes need to be finished
+        int time=0;
+        int i=0;
+        //calculate waiting times while there are uncompleted processes
+        while (!readyQueue.isEmpty())
+        {
+            //check if a process has finished
+            if (executeTIme[i]>=0) {
+                if (executeTIme[i] - quantum > 0) {
+                    //add time that have been passed
+                    time += quantum;
+                    //this is the remaining burst time for the process i
+                    executeTIme[i] -= quantum;
+
+                } else if (executeTIme[i] - quantum == 0) {
+                    //add time that have been passed
+                    time += quantum;
+                    //calculate the total waiting time
+                    waitingTime[i] = time - burstTime[i];
+
+                    //mark the process as finished
+                    executeTIme[i] = -1;
+                    //remove the process that have finished by shrinking queue's length
+                    readyQueue.remove(readyQueue.size()-1);
+
+                } else {
+                    //add time that have been passed
+                    time += executeTIme[i];
+                    //calculate the total waiting time
+                    waitingTime[i] = time - burstTime[i];
+
+                    //mark the process as finished
+                    executeTIme[i] = -1;
+                    //remove the process that have finished by shrinking queue's length
+                    readyQueue.remove(readyQueue.size()-1);
+                }
+            }
+            i++;
+            if(i>=n) i=0;
+        }
+
+        return waitingTime;
+    }
+
+
+    /**
+     * This method calculates turn around time for all processes
+     *
+     * @param burstTime an array with burst time for all processes
+     * @param waitingTime an array with waiting time for all processes
+     *
+     * @return an array with turnaround time for all processes
+     */
+    public int[] calcTurnAroundTime(int[] burstTime, int[] waitingTime)
+    {
+        int n= burstTime.length;
+        //initialize the turnaround time table
+        int[] turnAroundTime= new int [n];
+
+        //calculate turnaround time for each process (T.T= W.T + B.T)
+        for (int i=0; i<n;i++)
+            turnAroundTime[i]=waitingTime[i]+burstTime[i];
+
+        //return the turnaround time table
+        return turnAroundTime;
+    }
+
+
+    /**
+     * This method prints the results and calculates the average waiting and turnaround times
+     *
+     * @param burstTime an array with burst time for all processes
+     * @param quantum the quantum quantity
+     */
+    void printAvgTimes(int[] burstTime, int quantum)
+    {
+        int n = burstTime.length;
+        int totalWaitingTime = 0;
+        int totalTurnAroundTime = 0;
+
+        // Find waiting time of all processes
+        int[] waitingTime = calcWaitingTime(burstTime, quantum);
+
+        // Find turn around time for all processes
+        int[] turnAroundTime = calcTurnAroundTime(burstTime, waitingTime);
+
+        // Display processes along with all details
+        System.out.println("Process " + " Burst Time " +
+                " Waiting Time " + " Turnaround Time");
+        System.out.println("=======  ==========  ============  ===============");
+        // Calculate total waiting time and total turn around time
+        for (int i = 0; i < n; i++) {
+            totalWaitingTime += waitingTime[i];
+            totalTurnAroundTime += turnAroundTime[i];
+            System.out.println(i + "\t\t " + burstTime[i] +"\t\t\t " +
+                    waitingTime[i] +"\t\t\t   " + turnAroundTime[i]);
+        }
+
+        System.out.println("\nAverage waiting time = " +
+                (float)totalWaitingTime / (float)n);
+        System.out.println("Average turnaround time = " +
+                (float)totalTurnAroundTime / (float)n);
+    }
+}
+
diff --git a/src/test/java/com/others/RoundRobinTest.java b/src/test/java/com/others/RoundRobinTest.java
new file mode 100644
index 00000000..85eefbf3
--- /dev/null
+++ b/src/test/java/com/others/RoundRobinTest.java
@@ -0,0 +1,26 @@
+package src.test.java.com.others;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import src.main.java.com.others.RoundRobin;
+
+public class RoundRobinTest {
+    private final int[] burstTime = {5, 15, 4, 3};
+    private final RoundRobin roundRobin = new RoundRobin();
+
+    @Test
+    public void testWaitingTime(){
+        int[] expectedTime = {9,12,14,9};
+        int[] realtime= roundRobin.calcWaitingTime(burstTime,3);
+        Assert.assertArrayEquals(realtime, expectedTime);
+    }
+
+    @Test
+    public void testTurnAroundTIme(){
+        int[] expectedTIme={14,27,18,12};
+        int[] waitingTime = {9,12,14,9};
+        int[] realTime= roundRobin.calcTurnAroundTime(burstTime,waitingTime);
+        Assert.assertArrayEquals(realTime,expectedTIme);
+    }
+}