CC-14 : Simulate a Page Cache.

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

import java.util.*;
import java.util.Queue;

public class QueuePageFaultReplacement {
	
public int queuePageFaultReplacement(int[] pages, int pgCacheSize) throws Exception {
	HashSet< Integer > unqPages=new HashSet< Integer >();
	Queue< Integer > pgQueue=new LinkedList< Integer >();
	int faults=0; int removedPg;
	for (int idx=0; idx< pages.length; idx++) {
		if (unqPages.size() < pgCacheSize) {
			if (unqPages.contains(pages[idx])==false) {
				unqPages.add(pages[idx]);
				pgQueue.add(pages[idx]);
				faults++;
			}
		}else {
			if (unqPages.contains(pages[idx])==false) {
				removedPg=pgQueue.remove();
				unqPages.remove(removedPg);
				pgQueue.add(pages[idx]);
				unqPages.add(pages[idx]);
				faults++;
			}
		}
		System.out.println("New Page: "+pages[idx]);
		System.out.println("Pages Queue: ");
		printQueue(pgQueue);
		System.out.println("Faults count: "+faults);
	}	
	return faults;
}

public static void printQueue(Queue queue) throws Exception   {
    if (queue.size() == 0) { System.out.println("Queue empty"); return; }
    System.out.println();
	System.out.println("*********************************************************************");
	System.out.print("Queue nodes: ");
	Iterator itr=queue.iterator();
	while (itr.hasNext())  {
	    System.out.print(itr.next());
	    System.out.print(" <- ");
	} 
	System.out.println();
	System.out.println("*********************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;
}

public static void printArraySummary(int[] intArray, String label) throws Exception {
   	// Case 1: The input Array is null !!
	if (intArray == null) { System.out.println("\n\n Input Array was null !! \n"); return; }
	// Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("************************************************************************");
	System.out.print(label+" : ");
	int arrayIndex=0;
	for (arrayIndex=0; arrayIndex < intArray.length; arrayIndex++) {
			System.out.print(intArray[arrayIndex]);
			if (arrayIndex < intArray.length-1) {System.out.print(",");}
	} 
	System.out.println();
	System.out.println(" ************************************************************************");
		System.out.println();
		Thread.sleep(2000);
		return;
}


  	
public static void main(String[] args) {
	int retVal;
	try {
	QueuePageFaultReplacement queue=new QueuePageFaultReplacement();
	int[] arr= { 1,0,1,3,4,7,4,4,5,9,0,3,1};
	printArraySummary(arr, "Original Array:");
	retVal=queue.queuePageFaultReplacement(arr, 3);
	System.out.println("Final Faults count: "+retVal);
	
	}catch (Exception exception) {
		System.out.print("Exception: "+ exception);
	}
	
}
	
}