***** LLStack class ***** public class LLStack { private java.util.LinkedList li

Question

***** 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 < input.length(); 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.

Explanation / Answer

Please find my implementation.

public void reverseStack() {

      

       Queue queue = new Queue();

      

       while(!isEmpty()) {

           queue.enqueue(pop());

       }

      

       while(queue.isEmpty()) {

           this.push(queue.dequeue());

       }

   }

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