PageReplacementFIFO.java

import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;

class PageReplacementFIFO {
    static int pageFaults(int incomingStream[], int n, int frames) {
        System.out.println("Incoming \t Pages");

        HashSet s = new HashSet<>(frames);

        Queue queue = new LinkedList<>();

        int page_faults = 0;

        for (int i = 0; i < n; i++) {

            if (s.size() < frames) {

                if (!s.contains(incomingStream[i])) {
                    s.add(incomingStream[i]);
                    page_faults++;

                    queue.add(incomingStream[i]);

                }
            }

            else {

                if (!s.contains(incomingStream[i])) {

                    int val = (int) queue.peek();

                    queue.poll();

                    s.remove(val);

                    s.add(incomingStream[i]);

                    queue.add(incomingStream[i]);
                    page_faults++;

                }
            }

            System.out.print(incomingStream[i] + "\t\t");
            System.out.print(queue + " \n");
        }

        return page_faults;
    }

    public static void main(String args[]) {
        int incomingStream[] = { 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1 };
        int frames = 3;

        int len = incomingStream.length;
        int pageFaults = pageFaults(incomingStream, len, frames);
        int hit = len - pageFaults;

        System.out.println("Page faults: " + pageFaults);

    }
}