Question

You must use an array to hold the items in the queue. In other words, one of your fields should be an array for holding the items, but you may not have any other container fields (no other arrays, lists, stacks, queues, etc.) You will need at least one additional field (an int).

package hw5;

public class GeneralizedQueue {
  
/**
* Creates an empty queue.
*/
public GeneralizedQueue() {
// TODO
}
  
/**
* Checks if the queue is empty
* @return true if the queue is empty
* and false otherwise.
*/
public boolean isEmpty() {
// TODO
}
  
/**
* Add an item to the back of the queue.
* @param x the item to be addded to the queue
*/
public void insert(Item x) {
// TODO
}
  
/**
* delete and return the kth least recently inserted item
* (the kth item "in line".)
* @param k indicates which position from the queue to be removed.
* The first item is in position 1.
* @return the kth oldest item in the queue
*/
public Item delete(int k) {
// TODO
}
}

// CHECK AGAINST THE FOLLOWING TEST FILE

package hw5;

import static org.junit.Assert.*;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.Timeout;

public class HW5Test {

   @Rule
public Timeout globalTimeout = Timeout.seconds(1);
  
  
   @Test
   public void test() {
       Integer[] data = new Integer[10];
       for(int i = 0; i < data.length; i++)
           data[i] = new Integer(i);
       GeneralizedQueue<Integer> gq = new GeneralizedQueue<Integer>();
       for(int i = 0; i < data.length; i++) {
           gq.insert(data[i]);
       }
       // gq = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
       assertEquals(data[1], gq.delete(2)); // deletes 2nd item
       // gq = 0, 2, 3, 4, 5, 6, 7, 8, 9
       assertEquals(data[3], gq.delete(3)); // deletes 3rd item
       // gq = 0, 2, 4, 5, 6, 7, 8, 9
       assertEquals(data[5], gq.delete(4)); // deletes 4th item
       // gq = 0, 2, 4, 6, 7, 8, 9
   }

}

Answer 1

package hw5;

/* util package is use import Scanner class */
import java.util.*;
public class GeneralizedQueue {
int size; // total capacity of the queue
Integer queue[]; // array to hold the elements of the queue
int pointer; // specifies the index position of the last inserted item in the queue
/**
* Creates an empty queue.
*/
public GeneralizedQueue() {
Scanner sc=new Scanner(System.in);
System.out.print("Enter size of the queue :: ");
size = sc.nextInt();
queue = new Integer[size];
pointer = -1; // indicates that the queue is empty intially
for(int i = 0; i < queue.length; i++)
insert(new Integer(sc.nextInt())); //adds an element into the queue
}
  
/**
* Checks if the queue is empty
* @return true if the queue is empty
* and false otherwise.
*/
public boolean isEmpty() {
if(pointer == -1)
return true;
else
return false;
}
  
/**
* Add an item to the back of the queue.
* @param x the item to be addded to the queue
*/
public void insert(Integer x) {
if(pointer<size-1){ /* if the current pointer position is less than the capacity of queue */
pointer = pointer + 1; /* move the pointer to an empty location in the queue */
queue[pointer] = x; /* place the item in that location */
}else{
System.out.println("The queue is already full");
}


}
  
/**
* delete and return the kth least recently inserted item
* (the kth item "in line".)
* @param k indicates which position from the queue to be removed.
* The first item is in position 1.
* @return the kth oldest item in the queue
*/
public Integer delete(int k) {

System.out.println("Position to delete : " + k);
Integer item = new Integer(queue[k-1]); /* take the element at the k-1 index position */

System.out.println("Item deleted : " + item);
for(int i=k-1;i<pointer;i++) /* move the other elements one position before, overwritting the deleted item */
queue[i] = queue[i+1];
pointer = pointer - 1; /* reduce the pointer one location before */
return item;
}

public void displayQueue(){

System.out.println("Elements of queue : " );
for(int i=0;i<=pointer;i++)
System.out.println(queue[i]);
}

}

Sample Output