***** LLStack class *****

public class LLStack { private java.util.LinkedList list = new java.util.LinkedList(); public LLStack() { } public void clear() { list.clear(); } public boolean isEmpty() { return list.isEmpty(); } public Object topEl() { if (isEmpty()) throw new java.util.EmptyStackException(); return list.getLast(); } public Object pop() { if (isEmpty()) throw new java.util.EmptyStackException(); return list.removeLast(); } public void push(Object el) { list.add(el); } public String toString() { return list.toString(); } }

*** End of LLStack class ***

***** Queue Class ******

public class Queue { private java.util.LinkedList list = new java.util.LinkedList(); public Queue() { } public void clear() { list.clear(); } public boolean isEmpty() { return list.isEmpty(); } public Object firstEl() { return list.getFirst(); } public Object dequeue() { return list.removeFirst(); } public void enqueue(Object el) { list.add(el); } public String toString() { return list.toString(); } }

**** End of Queue Class ****

**** Stack class ****

public class Stack { private java.util.ArrayList pool = new java.util.ArrayList(); public Stack() { } public Stack(int n) { pool.ensureCapacity(n); } public void clear() { pool.clear(); } public boolean isEmpty() { return pool.isEmpty(); } public Object topEl() { if (isEmpty()) throw new java.util.EmptyStackException(); return pool.get(pool.size()-1); } public Object pop() { if (isEmpty()) throw new java.util.EmptyStackException(); return pool.remove(pool.size()-1); } public void push(Object el) { pool.add(el); } public String toString() { return pool.toString(); } }

***** End of stack class *****

*** Stack Test Class ****

import java.util.*;

public class StacksTest {

public static void main(String[] args) {

Stack s = new Stack();

s.push(new Integer(3));

s.push(new Integer(5));

s.push(new String("hi"));

while(!s.isEmpty()) {

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

}

s.clear(); //Empty the contents of the stack

System.out.println(" Here's how I reverse a string: ");

Scanner k = new Scanner(System.in);

System.out.print("Enter a string> ");

String input = k.nextLine();

for(int i = 0; i

s.push(input.charAt(i) + "");

System.out.println("The reversed string is: ");

while(!s.isEmpty()) {

System.out.print(s.pop());

}

System.out.println();

}

}

2. (15 points) Write a program reverseStack to reverse the order of elements on stack s using a Queue. Develop a test method that checks how your program runs when given a stack of Integers