An OS Project for simulating different Paging Algorithms.

Paging.java

package paging;

/**
 *
 * @author imraven
 */
import java.io.*;

public class Paging {
    
  BufferedReader input=new BufferedReader(new InputStreamReader(System.in));
	int n, page[], f, frames[], count;
	String[][] dframe = new String[50][50];

	public Paging() throws IOException{
		 System.out.println(" ____   _    ____ ___ _   _  ____      _    _     ____  ___  ____  ___ _____ _   _ __  __ ");
		 System.out.println("|  _ \\ / \\  / ___|_ _| \\ | |/ ___|    / \\  | |   / ___|/ _ \\|  _ \\|_ _|_   _| | | |  \\/  |");
		 System.out.println("| |_) / _ \\| |  _ | ||  \\| | |  _    / _ \\ | |  | |  _| | | | |_) || |  | | | |_| | |\\/| |");
		 System.out.println("|  __/ ___ \\ |_| || || |\\  | |_| |  / ___ \\| |__| |_| | |_| |  _ < | |  | | |  _  | |  | |");
		 System.out.println("|_| /_/   \\_\\____|___|_| \\_|\\____| /_/   \\_\\_____\\____|\\___/|_| \\_\\___| |_| |_| |_|_|  |_|");
                 System.out.println("		Project By: Raven Duran - Dimful Benantolis - Geoff Diaz		 BSIT 2R5");
	
		System.out.printf("\nNumber of page frames: ");
		f = Integer.parseInt(input.readLine());
		frames = new int[f];
		count = 1;
	}

	void reset(){
		int j;
		for(j=0;j<f;j++) { frames[j]=0; }
		count=1;
	}

	void read() throws IOException{
		int i;
		String sequence;
        String[] seq;
		
		System.out.println("Enter sequence of pages: (Ex: 2 3 1 5 1 ..)");
        sequence = input.readLine();
        seq = sequence.split(" ");
		
		n = seq.length;
		
		page = new int[n];
		for(i=0;i<n;i++){
			page[i]=Integer.parseInt( seq[i] );
		}
		for(i=0;i<f;i++) { frames[i]=-1; }
	}

	void fifo(){
		int i,j,k=0;
		reset();
		boolean found=false;
		for(i=0;i<n;i++){
			for(j=0;j<f;j++){
				if(page[i]==frames[j]) { found=true; }
			}
			if(found==false){
				frames[k]=page[i];
				if(k==f-1) {
						k=0;
					}
				else {
						k++;
					}
			}
			display();
			found=false;
		}
	}

	void lru(){
		int i,j,duration[],max;
		reset();
		duration=new int[f];
		boolean found=false;
		for(i=0;i<n;i++){
			for(j=0;j<f;j++) { duration[j]++; }
			for(j=0;j<f;j++){
				if(page[i]==frames[j]){
					found=true;
					duration[j]=0;
				}
			}
			if(found==false){
				max=0;
				for(j=0;j<f;j++){
					if(duration[j]>duration[max]) { max=j; }
				}
				frames[max]=page[i];
				duration[max]=0;
			}

			display();
			found=false;
		}
	}

	void opt(){
		int i,j=0,k,duration[],max,flag[];
		reset();
		duration = new int[f];
		flag = new int[f];
		boolean found=false;

		for(i=0;i<n;i++){
			for(j=0;j<f;j++){
				flag[j]=0;
				duration[j]=n;
			}

			for(k=i+1;k<n;k++){
				for(j=0;j<f;j++) {
					if(page[k]==frames[j]&&flag[j]==0){
						duration[j]=k;
						flag[j]=1;
					}
				}
			}

			for(j=0;j<f;j++) {
				if(page[i]==frames[j]) {found = true;}
			}
			if(found==false){
				max=0;
				for(j=0;j<f;j++){
					if(duration[j]>duration[max]) {max=j;}
					if(frames[j]<0){
						max=j;
						break;
					}
				}
				frames[max]=page[i];
			}
			display();
			found=false;
		}
	}

	void display(){
		int i;
		for(i=0;i<f;i++){
			if(frames[i]==-1 || frames[i] == 0) { dframe[i][count-1] = "-"; }
			else { dframe[i][count-1] = ""+frames[i]; }
		}
		
		count++;
	}

	public static void main(String[] args) throws IOException{
		int option;
		String choice;
		Paging p = new Paging();
		p.read();
		BufferedReader input=new BufferedReader(new InputStreamReader(System.in));
		do{
			System.out.println("\nChoose Algorithm");
			System.out.println("1. FIFO");
			System.out.println("2. LRU");
			System.out.println("3. OPT");
			System.out.print("\nEnter option: ");
			option=Integer.parseInt(input.readLine());
			switch(option){
				case 1: p.fifo();
				break;
				case 2: p.lru();
				break;
				case 3: p.opt();
				break;
				default: 
                                    System.out.println("Invalid input");
                                    System.exit(0);
			}
			
			System.out.printf("\n");
			int i,j;
                        for (i = 0; i <= p.n; i++){ 
                            if (i == 0){System.out.printf(" %-2s    "," "); } 
                            else { System.out.printf(" %-2d |",i); }
                        }
                        System.out.printf("\n");
			for (i = 0; i < p.f; i++){
                                System.out.printf(" %-2d |  ",i);
				for (j = 0; j < p.n; j++){
					System.out.printf(" %-2s |",p.dframe[i][j]);
				}
				System.out.printf("\n");
			}
			
			System.out.println("Press C to continue");
			choice=input.readLine();
		} while(choice.compareToIgnoreCase("c")==0);
	}
}