First Come First Serve ( FCFS ) in java

On-campus and online computer science courses to Learn the basic concepts of Computer Science.This tutorial will cover c ,c++, java, data structure and algorithm,computer graphics,microprocessor,analysis of algorithms,Digital Logic Design and Analysis,computer architecture,computer networks,operating system.

code in Java:

import java.io.*;
public class FCFS {
 
 public static void main(String args[]) throws IOException
 {
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      int n;
      System.out.println("Please enter the number of Processes: ");
       n = Integer.parseInt(br.readLine());
       int proc[][] = new int[n + 1][4];
       for(int i = 1; i <= n; i++)
       {
      System.out.println("Please enter the Burst Time for Process " + i + ": ");
      proc[i][1] = Integer.parseInt(br.readLine());
     }
       System.out.println();
       
       //Calculation of Total Time and Initialization of Time Chart array
     int total_time = 0;
     for(int i = 1; i <= n; i++)
     {
      total_time += proc[i][1];
     }
     int time_chart[] = new int[total_time];
     
     int sel_proc = 1;
     
     for(int i = 0; i < total_time; i++)
     { 
      //Assign selected process to current time in the Chart
      time_chart[i] = sel_proc;
      
      //Decrement Remaining Time of selected process by 1 since it has been assigned the CPU for 1 unit of time
      proc[sel_proc][1]--;
      
      //WT and TT Calculation
      for(int j = 1; j <= n; j++)
      {
       if(proc[j][1] != 0)
       {
        proc[j][3]++;//If process has completed execution its TT is incremented by 1
        if(j != sel_proc)//If the process has not been currently assigned the CPU its WT is incremented by 1
         proc[j][2]++;
       }
       else if(j == sel_proc)//This is a special case in which the process has been assigned CPU and has completed its execution
        proc[j][3]++;
      }
      
      //Printing the Time Chart
      if(i != 0)
      {
       if(sel_proc != time_chart[i - 1])
        //If the CPU has been assigned to a different Process we need to print the current value of time and the name of 
        //the new Process
       {
        System.out.print("--" + i + "--P" + sel_proc);
       }
      }
      else//If the current time is 0 i.e the printing has just started we need to print the name of the First selected Process
       System.out.print(i + "--P" + sel_proc);
      if(i == total_time - 1)//All the process names have been printed now we have to print the time at which execution ends
       System.out.print("--" + (i + 1));
      
      //If current process has been completed we select the next process from the list
      if(proc[sel_proc][1] == 0)
       sel_proc++;
      
     }
     System.out.println();
     System.out.println();
     
     //Printing the WT and TT for each Process
     System.out.println("P\t WT \t TT ");
     for(int i = 1; i <= n; i++)
     {
      System.out.printf("%d\t%2dms\t%2dms",i,proc[i][2],proc[i][3]);
      System.out.println();
     }
     
     System.out.println();
     
     //Printing the average WT & TT
     float WT = 0,TT = 0;
     for(int i = 1; i <= n; i++)
     {
      WT += proc[i][2];
      TT += proc[i][3];
     }
     WT /= n;
     TT /= n;
     System.out.println("The Average WT is: " + WT + "ms");
     System.out.println("The Average TT is: " + TT + "ms");
 }
}

output:-

Please enter the number of Processes: 
3
Please enter the Burst Time for Process 1: 
24
Please enter the Burst Time for Process 2: 
3
Please enter the Burst Time for Process 3: 
3

0--P1--24--P2--27--P3--30

P  WT   TT 
1  0ms 24ms
2 24ms 27ms
3 27ms 30ms

The Average WT is: 17.0ms
The Average TT is: 27.0ms
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