Priority_Scheduling.java

package java_algo;

//Java program for implementation of FCFS
//scheduling
import java.util.*;

class Process
{
	int pid; // Process ID
	int bt; // CPU Burst time required
	int priority; // Priority of this process
	Process(int pid, int bt, int priority)
	{
		this.pid = pid;
		this.bt = bt;
		this.priority = priority;
	}
	public int prior() {
		return priority;
	}
}


public class Priority_Scheduling
{

//Function to find the waiting time for all
//processes
public void findWaitingTime(Process proc[], int n,
					int wt[])
{

	// waiting time for first process is 0
	wt[0] = 0;

	// calculating waiting time
	for (int i = 1; i < n ; i++ )
		wt[i] = proc[i - 1].bt + wt[i - 1] ;
}

//Function to calculate turn around time
public void findTurnAroundTime( Process proc[], int n,
						int wt[], int tat[])
{
	// calculating turnaround time by adding
	// bt[i] + wt[i]
	for (int i = 0; i < n ; i++)
		tat[i] = proc[i].bt + wt[i];
}

//Function to calculate average time
public void findavgTime(Process proc[], int n)
{
	int wt[] = new int[n], tat[] = new int[n], total_wt = 0, total_tat = 0;

	// Function to find waiting time of all processes
	findWaitingTime(proc, n, wt);

	// Function to find turn around time for all processes
	findTurnAroundTime(proc, n, wt, tat);

	// Display processes along with all details
	System.out.print("\nProcesses Burst time Waiting time Turn around time\n");

	// Calculate total waiting time and total turn
	// around time
	for (int i = 0; i < n; i++)
	{
		total_wt = total_wt + wt[i];
		total_tat = total_tat + tat[i];
		System.out.print(" " + proc[i].pid + "\t\t" + proc[i].bt + "\t " + wt[i] + "\t\t " + tat[i] + "\n");
	}

	System.out.print("\nAverage waiting time = "
			+(float)total_wt / (float)n);
	System.out.print("\nAverage turn around time = "+(float)total_tat / (float)n);
}

public void priorityScheduling(Process proc[], int n)
{

	// Sort processes by priority
	Arrays.sort(proc, new Comparator<Process>() {
		@Override
		public int compare(Process a, Process b) {
			return b.prior() - a.prior();
		}
	});
	System.out.print("Order in which processes gets executed \n");
	for (int i = 0 ; i < n; i++)
		System.out.print(proc[i].pid + " ") ;

	findavgTime(proc, n);
}

//Driver code
public static void main(String[] args)
{
	Priority_Scheduling ob=new Priority_Scheduling();
	int n = 3;
	Process proc[] = new Process[n];
	proc[0] = new Process(1, 8, 2);
	proc[1] = new Process(2, 5, 3);
	proc[2] = new Process(9, 8, 1);
	ob.priorityScheduling(proc, n);
}
}