Question $3$:

Write a method in the Demo class $($name it reverseString$),$ call the method from the main$()$ and pass a string to it$.$ This method will do the following:

Receives a string $($sentence$,$ not just one word$).$

Stores the received string in an linkedlist$-$based stack

Prints the sentence in reverse.

Example:

Call statement: reverseString$("$Testing my reverseString method"$)$;

output: dohtem gnirtSesrever ym gnitseT

$**$Demo class below$**$

public class LinkedListStackDemo $\{$

public static void main$($String$[]$ args$)\{$

LinkedStack LS $=$ new LinkedStack$()$;

LS$.$push$("$Test$")$;

LS$.$push$("$Testing$")$;

LS$.$push$("$Tested$")$;

System.out.println$($LS$)$;

int numEl $=$ LS$.$numValues$()$;

System.out.println$("$Number of elements stored in stack: $"+$ numEl$)$;

$\}$

$//$reverseString class

public static void reverseString$($String sentence$)\{$

LinkedStack st $=$ new LinkedStack$()$;

$\}$

$**$LinkedStack class below$**$

public class LinkedStack $\{$

private Node top $=$ null;

public boolean empty$()\{$

return top $==$ null;

$\}$

public void push$($String s$)\{$

top $=$ new Node$($s$,$ top$)$;

$\}$

public String pop$()\{$

String retValue;

if $($empty$())\{$

throw new IllegalStateException$()$;

$\}$ else $\{$

retValue $=$ top.element;

top $=$ top.next;

return retValue;

$\}$

$\}$

public String peek$()\{$

if $($empty$())\{$

throw new IllegalStateException$()$;

$\}$ else $\{$

return top.element;

$\}$

$\}$

public int numValues$()\{$

int count $=0$;

Node curr $=$ top;

while $($curr $!=$ null$)\{$

count$++$;

curr $=$ curr.next;

$\}$

return count;

$\}$

public String toString$()\{$

Node ref $=$ top;

String toPrint $=""$;

while $($ref $!=$ null$)\{$

toPrint $+=","+$ ref.element;

ref $=$ ref.next;

$\}$

return "The elements in the stack reversed are: $"+$ toPrint;

$\}$

$//$ Node class used for linked list

private class Node $\{$

String element;

Node next;

Node$($String e$,$ Node n$)\{$

element $=$ e;

next $=$ n;

$\}$

$\}$