Page_Replacement_FCFS.java

import java.util.HashSet;
import java.util.LinkedList;
import java.util.Queue;
class Test{
    static int page_Faults(int pages[], int n, int capacity){
        HashSet<Integer> s = new HashSet<>(capacity);
        Queue<Integer> indexes = new LinkedList<>() ;
        int page_faults = 0;
        for (int i = 0; i < n; i++){
            if (s.size() < capacity){
                if (!s.contains(pages[i])){
                    s.add(pages[i]);
                    page_faults++;
                    indexes.add(pages[i]);
                }
            }
            else{
                if (!s.contains(pages[i])){
                    int val = indexes.peek();
      
                    indexes.poll();
                    s.remove(val);
                    s.add(pages[i]);
                    indexes.add(pages[i]);
                    page_faults++;
                }
            }
        }
        return page_faults;
    }
    
    public static void main(String args[]){
        int pages[] = {8, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 0};
  
        int capacity = 3;
        System.out.println(page_Faults(pages, pages.length, capacity));
    }
}