Palindrome with Stack Java

import java.util.Scanner;

public class Stack<T> {

    private int stackPos;
    private T[] stack;

    public Stack() {
        this.stackPos = -1;
        this.stack = (T[]) new Object[100];
    }

    public void push(T value) {
        if (this.stackPos < this.stack.length - 1) {
            this.stack[++stackPos] = value;
        }
    }

    public T pop() {
        if (this.isEmpty()) {
            return null;
        }
        return this.stack[stackPos--];
    }

    public int length() {
        if (this.isEmpty()) {
            return 0;
        }
        return this.stackPos + 1;
    }

    public T head() {
        if (this.isEmpty()) {
            return null;
        }
        return this.stack[stackPos];
    }

    public boolean isEmpty() {
        return this.stackPos == -1;
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        Stack<Character> stack = new Stack<Character>();

        String answer = input.nextLine();

        for (int i = 0; i < answer.length(); i++) {
            stack.push(answer.charAt(i));
        }

        String reverseAnswer = "";
        while (!stack.isEmpty()) {
            reverseAnswer += stack.pop();
        }

        if (answer.equals(reverseAnswer))
            System.out.println("É um palindromo");
        else
            System.out.println("Não é um palindromo");
    }

}