SJF_Scheduling.java

package java_algo;

import java.util.*;

public class SJF_Scheduling {
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		System.out.println("enter no of process:");
		int n = sc.nextInt();
		int pid[] = new int[n];
		int at[] = new int[n]; // at means arrival time
		int bt[] = new int[n]; // bt means burst time
		int ct[] = new int[n]; // ct means complete time
		int ta[] = new int[n]; // ta means turn around time
		int wt[] = new int[n]; // wt means waiting time
		int f[] = new int[n]; // f means it is flag it checks process is completed or not
		int st = 0, tot = 0;
		float avgwt = 0, avgta = 0;

		for (int i = 0; i < n; i++) {
			System.out.println("enter process " + (i + 1) + " arrival time:");
			at[i] = sc.nextInt();
			System.out.println("enter process " + (i + 1) + " brust time:");
			bt[i] = sc.nextInt();
			pid[i] = i + 1;
			f[i] = 0;
		}
		boolean a = true;
		while (true) {
			int c = n, min = 999;
			if (tot == n) // total no of process = completed process loop will be terminated
				break;
			for (int i = 0; i < n; i++) {
				/*
				 * If i'th process arrival time <= system time and its flag=0 and burst<min That
				 * process will be executed first
				 */
				if ((at[i] <= st) && (f[i] == 0) && (bt[i] < min)) {
					min = bt[i];
					c = i;
				}
			}
			/*
			 * If c==n means c value can not updated because no process arrival time< system
			 * time so we increase the system time
			 */
			if (c == n)
				st++;
			else {
				ct[c] = st + bt[c];
				st += bt[c];
				ta[c] = ct[c] - at[c];
				wt[c] = ta[c] - bt[c];
				f[c] = 1;
				tot++;
			}
		}
		System.out.println("\npid  arrival  brust  complete turn waiting");
		for (int i = 0; i < n; i++) {
			avgwt += wt[i];
			avgta += ta[i];
			System.out.println(pid[i] + "\t" + at[i] + "\t" + bt[i] + "\t" + ct[i] + "\t" + ta[i] + "\t" + wt[i]);
		}

		System.out.println("Gantt Chart : ");

		
		// first sort process id according toarrival time
		int temp = 0;
		for (int i = 0; i < ct.length; i++) {
			for (int j = i + 1; j < ct.length; j++) {
				if (ct[i] > ct[j]) {
					temp = ct[i];
					ct[i] = ct[j];
					ct[j] = temp;

					temp = pid[i];
					pid[i] = pid[j];
					pid[j] = temp;

				}
			}
		}

		for (int i = 0; i <= n; i++) {
			System.out.print(" ------");
		}

		System.out.println();
		for (int i = 0; i < n; i++) {
			System.out.print("|  P" + pid[i] + "  ");
		}
		System.out.print("|");
		System.out.println();

		System.out.print(0 + "------");
		for (int i = 0; i < n; i++) {

			System.out.print(ct[i] + "-----");

		}

		System.out.println("\naverage tat is " + (float) (avgta / n));
		System.out.println("average wt is " + (float) (avgwt / n));
		sc.close();
	}
}