PLease i need a helping hand

Question

Please could someone help me with the following code to check if a stack is empty or not.
i have written this code button it doesnt correctly identify when a stack is empty or not.
N.b I can not use any java built in classes or methods to check. I have been given a node class to use and i need to return true if the stack is empty or false if there is something in there.
Many Thanks for any help
Heres the code:
public boolean isEmpty() {
if((top.next==null && top.data==null) || top.data==""){
return true;
else{
return false;
}

Answer 1

levi from your code i have extracted the parts that i need here is my final code:
public class Question2 {
private Node top;
private Question1 check;
/* You NEED to IMPLEMENT a constructor with NO arguments. This */
/* constructor should initialize this class. */
public Question2() {
top = null;
/* This method pushes a ZML start tag onto the top of the stack. */
public void pushTag(String startTag) throws TagError {
top = new Node(startTag, top);
} // end of metod pushTag
/* This methods pops a ZML start tag of the top of the stack. Should */
/* the stack be empty, then the exception "StackEmpty" is thrown. */
public String popTag() throws StackEmpty { 
return top.data;
} // end of method popTag
/* This method returns "true" if the stack is empty, otherwise it */
/* returns "false". */
public boolean isEmpty() {
return top == null;
} // end of method isEmpty
} // end of class Question2
in the poptag method it is only a string return value, so would i have to run a loop or something which moves all the nodes up one place, and if this code was placed after the return value would it not get executed
Many Thanks for any help anyone can offer