CodeRelease #1: Integer List ADT in Java

ListADT.java

package release;

import java.util.Scanner;

public class ListADT
{
	private int[] listArray;
	//  integer array to hold 'int' type list elements

	private int listBottom;
	//  integer variable listBottom to keep track of the listBottom of the list

	//  constructor to initialize values for the ADT class
	public ListADT(int numberOfElements)
	{
		listArray = new int[numberOfElements];
		//  add memory to the array for n elements, n = numberOfElements

		listBottom = -1;
		//  since the list is currently empty, the index of listBottom is -1
	}

	//  push method for the list
	public void insert(int element)
	{
		if (isFull())
		//  check whether the list is already full
		{
			System.out.println("List is already full!");
			//  if the list is already full, print the message
		}
		else
		{
			listBottom++;
			//  increase the listBottom index

			listArray[listBottom] = element;
			//  add the new element at the modified index
		}
	}

	// isFull method for the list
	public boolean isFull()
	{
		boolean response = false;
		//  response variable to return the value of the method

		if (listBottom == listArray.length - 1)
		//  check whether the listBottom index is same as the last index of the array
		{
			response = true;
			//  if true, set the response variable to true
		}

		return response;
	}

	// method to remove the last element of the list
	public int remove()
	{
		int response = 0;

		if (isEmpty())
		{
			System.out.println("The list is already empty!");
		}
		else
		{
			response = listArray[listBottom];
			listArray[listBottom] = 0;
			//  set the last element of the list to 0, indicating it has been deleted

			listBottom--;
			//  decrease the list bottom index
		}

		return response;
	}

	// removeAt() method to remove a specific index from the list
	public int removeAt(int index)
	{
		int response = 0;

		if (isEmpty())  //  check whether the list is empty
		{
			System.out.println("List is already empty");
		}
		else
		{
			if (listBottom < index) //  if bottom is less than index
			// then the index is not present in the list
			{
				System.out.println("No such index in the list!");
			}
			else
			{
				response = listArray[index];
				listArray[index] = 0;   //  set the element at 'index' to 0 (delete)
				//  shift the elements to the left
				int i;
				for (i = index; i < listBottom - 1; i++)
				{
					listArray[i] = listArray[i + 1];
				}
				listArray[i] = 0;   // delete the last redundant value
				listBottom--;
			}
		}

		return response;
	}

	// isEmpty method for the list
	public boolean isEmpty()
	{
		boolean response = false;

		if (listBottom == -1)
		//  check whether the bottom index is -1 (empty condition for the list)
		{
			response = true;
		}

		return response;
	}

	//  a display method for the list
	public void display()
	{
		System.out.println("---");
		if (isEmpty())
		{
			System.out.println("List is empty!");
		}
		else
		{
			for (int i : listArray)
			{
				if (i != 0)
				{
					System.out.println(i);
				}
			}
		}
		System.out.println("---");
	}

	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);

		System.out.println("How many elements would you like in your list?");

		int n = scanner.nextInt();  //  input the number of elements in the list

		ListADT listObject = new ListADT(n);
		/*
		 * n is passed inside the constructor to the class to specify that
		 * the listArray must have n elements.
		 * */

		listObject.display();

		//  iterate the loop 'n' times to input 'n' elements
		for (int i = 0; i < n; i++)
		{
			System.out.print("Enter the " + i + "th element:");
			int value = scanner.nextInt();
			listObject.insert(value);
		}

		System.out.println("List after inserting " + n + " elements.");
		listObject.display();

		System.out.println(listObject.remove() + " was removed from the list.");

		System.out.println("List after removing the last element.");
		listObject.display();


		System.out.println("Enter the index you want to remove:");
		int removedElement = listObject.removeAt(scanner.nextInt());
		System.out.println(removedElement + " was removed");

		System.out.println("List after removing " + removedElement);
		listObject.display();

	}

}