I am new in data structure. I perform append and palindrome or not operation but i get Cannot Find Symbol error while initize popFromStack variable and i am stuck there...

Here down is my code:

class Node
{
    String data;
    Node next;
    Node(String data)
    {
        this.data = data;
    }
}

public class MyClass {
    Node head;
    public void append(String data)
    {
        if(head == null)
        {
            head = new Node(data);
            return;
        }
        
        Node current = head;
        while(current.next != null)
        {
            current = current.next;
        }
        current.next = new Node(data);
    }
    
    public boolean isPalindrome(Node head)
    {
        Node slow = head;
        boolean isPalin = true;
        Stack<String> stack = new Stack<String>();;
        
        while(slow != null)
        {
            stack.push(slow.data);
            slow = slow.next;
        }
        
        while(head != null)
        {
            String popFromStack = stack.pop; // here is the problem
            if(head.data == popFromStack)
            {
                isPalin = true;
            }
            else
            {
                isPalin = false;
            }
            head = head.next;
            return isPalin;
        }
    }

    public void printList()
    {
        Node current = head;
        while(current != null)
        {
            System.out.print(current.data   " ");
            current = current.next;
        }
    }

    public static void main(String[] args) {
        MyClass m = new MyClass();        
        m.append("A");
        m.append("B");
        m.append("D");
        m.append("B");
        m.append("A");
        m.printList();
        
        
        System.out.println("\n");
        System.out.print("Palindrome : "   m.isPalindrome(m.head));
    }
        

Stack trace:

MyClass.java:79: error: cannot find symbol
            String popFromStack = stack.pop;
                                       ^
  symbol:   variable pop
  location: variable stack of type Stack<String>
1 error

CodePudding user response：

pop is a method so you must add ()

String popFromStack = stack.pop();

Btw. you must not compare String with == but with calling equals.

if(head.data.equals(popFromStack))

Please read more about String comparision: https://www.javatpoint.com/string-comparison-in-java

CodePudding user response：

pop is not an attribute, it's a method. make it like this:

stack.pop();