Implementation of Shortest Job First Scheduling algorithm

Shortest Job First (SJF)

• Best approach to minimize waiting time.
• Impossible to implement
• Processer should know in advance how much time process will take

import java.util.Scanner;
class Sjf
{
Scanner sc=new Scanner(System.in);

int MaxProcess=sc.nextInt();

int Pid[]=new int[MaxProcess];

int Burst[]=new int[MaxProcess];

int Wait[]=new int[MaxProcess];

int Trt[]=new int[MaxProcess];

int Arrival[]=new int[MaxProcess];

void input()

{

for(int i=0;i<MaxProcess;i++)

{

System.out.format("enter the process-id for this %d",(i+1));

Pid[i]=sc.nextInt();

System.out.format("enter the burst time for this p%d",Pid[i]);

Burst[i]=sc.nextInt();

System.out.format("enter the arrival time for this p%d",Pid[i]);

Arrival[i]=sc.nextInt();

}

    System.out.println("the process-id and burst time is:\n");

    System.out.println("process-id\t\tbursttime\t\tarrival\n");

for(int i=0;i<MaxProcess;i++)

{

System.out.format("%d\t\t\t%d\t\t\t%d\n",Pid[i],Burst[i],Arrival[i]);

}

}

void turnAroundTime()

{

for(int i=0;i<MaxProcess;i++)

{

Trt[i]=Wait[i]+Burst[i];

}

}

void waitingTime()

{

int i,Total;

Wait[0]=0;

Total=Arrival[0];

for(i=1;i<MaxProcess;i++)

{

Total=Total+Burst[i-1];

Wait[i]=Total-Arrival[i];;

}

}

void displaySort()

{

System.out.println("after sorting on the basis of arrival time:");

float sum1=0,sum2=0;

System.out.println("process-id\t bursttime\t arrival \t waiting time\t turnaroundtime\n");

for(int i=0;i<MaxProcess;i++)

System.out.format("%d\t\t\t%d\t\t%d\t\t%d\t\t%d\n",Pid[i],Burst[i],Arrival[i],Wait[i],Trt[i]);

}

void display()

{

float sum1=0,sum2=0;

System.out.println("process-id\t bursttime\t arrival \t waiting time\t turnaroundtime\n");

for(int i=0;i<MaxProcess;i++)

System.out.format("%d\t\t\t%d\t\t%d\t\t%d\t\t%d\n",Pid[i],Burst[i],Arrival[i],Wait[i],Trt[i]);

for(int i=0;i<MaxProcess;i++)

{

sum1=sum1+Wait[i];

sum2=sum2+Trt[i];

}

System.out.format("waiting time is %f\n",sum1/MaxProcess);

System.out.format("totalrunaroundtime is %f\n",sum2/MaxProcess);

}

void sort()

{

for(int i=0;i<MaxProcess-1;i++)

{

  for(int j=i+1;j<MaxProcess;j++)

{

if(Burst[i]>Burst[j])

{

int temp1=Arrival[i];

Arrival[i]=Arrival[j];

Arrival[j]=temp1;

int temp2=Burst[i];

Burst[i]=Burst[j];

Burst[j]=temp2;

int temp3=Pid[i];

Pid[i]=Pid[j];

Pid[j]=temp3;

}

}

}

int temp=0;

int min=Arrival[0];

for(int i=1;i<MaxProcess;i++)

{

if(min>Arrival[i])

{

min=Arrival[i];

temp=i;

}

}

int f1=Arrival[temp];

int f2=Burst[temp];

int f3=Pid[temp];

for(int i=temp;i>0;i--)

{

Arrival[i]=Arrival[i-1];

Burst[i]=Burst[i-1];

Pid[i]=Pid[i-1];

}

Burst[0]=f2;

Arrival[0]=f1;

Pid[0]=f3;

}

void drawGanttChart()

{

System.out.println();

for(int i=0;i<MaxProcess;i++)

{

  for(int j=0;j<Burst[i];j++)

System.out.print("|");

System.out.format(" p%d ",Pid[i]);

}

}

}

class SjfTest

{

public static void main(String args[])

{

System.out.println("enter the total number of process:");

Sjf s1=new Sjf();

s1.input();

s1.sort();

s1.displaySort();

s1.waitingTime();

s1.turnAroundTime();

s1.display();

s1.drawGanttChart();

}

}