DataSection27

// Guide to Data Structures
// Section 2.7
// Copyright 2018, by J.T. Streib and T. Soma

import java.util.*;

public class PalindromeVersion2 {
public static void main(String args[]) {

Scanner scanner = new Scanner(System.in);
int i, j;
String word;
boolean isPalindrome;
StackArrayGeneric<Character> stack;

System.out.print("Enter a word: ");
word = scanner.next();
stack = new StackArrayGeneric<Character>(word.length()/2);

for(i=0; i<word.length()/2; i++)
  stack.push(word.charAt(i));

j = i;
if(word.length()%2 != 0)
j++;

isPalindrome = true;
while(!stack.empty() && isPalindrome) {
  if(stack.pop() != word.charAt(j))
     isPalindrome = false;
  j++;
}

if(isPalindrome)
  System.out.println("The word you entered is a palindrome.");
else
  System.out.println("The word you entered is NOT a palindrome.");
}
}

public class StackArrayGeneric<T> {
private static final int N = 3;
private int top;
private T[] sarray;

// constructors
public StackArrayGeneric() {
this(N);
}

public StackArrayGeneric(int n) {
top = 0;
sarray = (T[]) new Object[n];
}

// value returning methods
public boolean empty() {
return top <= 0;
}

private boolean full() {
return top >= sarray.length;
}

public T pop() {
T item = null;
if(empty())
  throw new RuntimeException("Stack is empty");
top--;
item = sarray[top];
return item;
}

// void method
public void push(T item) {
if(full())
  throw new RuntimeException("Stack is full");
sarray[top]=item;
top++;
}
}