Question

Write a program that uses a stack to reverse its inputs. Your stack must be generic and you must demonstrate that it accepts both String and Integer types. Your stack must implement the following methods:

push,

pop,

isEmpty (returns true if the stack is empty and false otherwise), and

size (returns an integer value for the number of items in the stack).

You may use either an ArrayList or a LinkedList to implement your stack. Also, your pop method must throw an IndexOutOfBoundsException if the user attempts to “pop” something off an empty stack. Name your stack class “Stack” and put it in a file named Stack.java.

Create a StackTest.java file to demonstrate all of the methods of your stack. Instantiate two stacks; one for String and one for Integer. Push words/integers onto your stack. After you have pushed a series of words/integers on your stack use a while loop to pop and print each item. If your stack is working properly your inputs should print in reverse order. Be sure that you calls to pop are in a try statement and will catch the IndexOutOfBoundsException, if thrown.

Note: Java has a Stack class, but you may not use it. You must create your own Stack class and your class must have the following operations (all of which must be demonstrated): push, pop, isEmpty, and size.

Here is an example screen shot of a working stack that reverses words and integers:

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// Stack.java

import java.util.ArrayList;

public class Stack<T> {

      //underlying data structure

      private ArrayList<T> stk;

     

      //default constructor

      public Stack() {

            //initializing array list

            stk = new ArrayList<T>();

      }

     

      //adds an element to the top

      public void push(T item) {

            //simply adding

            stk.add(item);

      }

     

      //removes and returns an element from top

      public T pop() {

            if (stk.isEmpty()) {

                  //stack is empty, throwing exception

                  throw new IndexOutOfBoundsException("Cannot pop from empty Stack!");

            }

            //removing and returning last element

            return stk.remove(stk.size()-1);

      }

     

      //returns true if stack is empty

      public boolean isEmpty() {

            return stk.isEmpty();

      }

     

      //returns the current size of stack

      public int size() {

            return stk.size();

      }

}

// StackTest.java

public class StackTest {

      public static void main(String[] args) {

            //creating a String stack

            Stack<String> stringStack = new Stack<String>();

            //creating a String

            String str = "The rain in Spain";

            System.out.println("Pushing on to the stack: \"" + str + "\"");

            //splitting str by white space, looping through each string

            for (String word : str.split(" ")) {

                  //adding to string stack

                  stringStack.push(word);

            }

            System.out.println("The size of the String stack is "

                        + stringStack.size());

            System.out.println("Stack is empty? " + stringStack.isEmpty());

            System.out.println("Popping elements off the stack");

            //looping and popping each element from stack, displaying it

            while (!stringStack.isEmpty()) {

                  try {

                        System.out.print(stringStack.pop() + " ");

                  } catch (IndexOutOfBoundsException ex) {

                        System.out.println(ex.getMessage());

                  }

            }

            System.out.println("\nStack is empty? " + stringStack.isEmpty());

            System.out.println("The size of the String stack is "

                        + stringStack.size());

            System.out.println("\n\n");

            //creating an integer stack

            Stack<Integer> intStack = new Stack<Integer>();

            //creating a String containing some integers

            str = "1 2 3 4 5";

            System.out.println("Pushing on to the Integer stack: \"" + str + "\"");

            //splitting str by white space, looping through each string

            for (String number : str.split(" ")) {

                  //converting current string to integer, adding to integer stack

                  intStack.push(Integer.parseInt(number));

            }

            System.out.println("The size of the Integer stack is "

                        + intStack.size());

            System.out.println("Stack is empty? " + intStack.isEmpty());

            System.out.println("Popping elements off the stack");

            //looping and popping each element from stack, displaying it

            while (!intStack.isEmpty()) {

                  try {

                        System.out.print(intStack.pop() + " ");

                  } catch (IndexOutOfBoundsException ex) {

                        System.out.println(ex.getMessage());

                  }

            }

            System.out.println("\nStack is empty? " + intStack.isEmpty());

            System.out.println("The size of the Integer stack is "

                        + intStack.size());

      }

}

/*OUTPUT*/

Pushing on to the stack: "The rain in Spain"

The size of the String stack is 4

Stack is empty? false

Popping elements off the stack

Spain in rain The

Stack is empty? true

The size of the String stack is 0

Pushing on to the Integer stack: "1 2 3 4 5"

The size of the Integer stack is 5

Stack is empty? false

Popping elements off the stack

5 4 3 2 1

Stack is empty? true

The size of the Integer stack is 0