README.md

CPUScheduler

Java implementation of 6 CPU scheduling algorithms: First Come First Serve (FCFS), Shortest Job First (SJF), Shortest Remaining Time (SRT), Priority Non-preemptive (PSN), Priority Preemptive (PSP), and Round Robin (RR).

Usage

Instantiate a CPUScheduler object of the algorithm

CPUScheduler fcfs = new FirstComeFirstServe();

Add a new Row for every job queued

fcfs.add(new Row("P1", 0, 5));
fcfs.add(new Row("P2", 2, 4));
fcfs.add(new Row("P3", 4, 3));
fcfs.add(new Row("P4", 6, 6));

Call the process method

fcfs.process();

Use the accessors

fcfs.getAverageWaitingTime();     // 3.5
fcfs.getAverageTurnAroundTime();  // 8.0

Round Robin

In the case of RoundRobin, you must first set a time quantum before calling process.

CPUScheduler rr = new RoundRobin();

rr.add(new Row("P1", 0, 5));
rr.add(new Row("P2", 2, 4));
rr.add(new Row("P3", 4, 3));
rr.add(new Row("P4", 6, 6));

rr.setTimeQuantum(2);
rr.process();

Rows

Using the object's getRows method will return a List of all queued Row. After process, each Row will reflect their respective computed waiting time and turnaround time.

CPUScheduler sjf = new ShortestJobFirst();
List<Row> rows;

sjf.add(new Row("P1", 0, 5));
sjf.add(new Row("P2", 2, 4));

rows = sjf.getRows();
rows.get(1).getWaitingTime();     // 0
rows.get(1).getTurnaroundTime();  // 0

sjf.process();

rows = sjf.getRows();
rows.get(1).getWaitingTime();     // 3
rows.get(1).getTurnaroundTime();  // 7

Timeline

Using the object's getTimeline method will return a List of Event which can be used to draw a Gantt chart. The timeline shows what job is being processed at the given time.

List<Event> timeline = fcfs.getTimeline();

for (Event event : timeline)
{
  System.out.println(event.getStartTime());
  System.out.println("|  " + event.getProcessName());
}

System.out.print(timeline.get(timeline.size() - 1).getFinishTime());

Result:

0
|  P1
5
|  P2
9
|  P3
12
|  P4
18

Example

An example can be found here.

Demo

A Java Swing application using the library is included within the project.

Screenshots