Get call in stack Java

   public void push(E e)
  {
    list.add(e);
   }
public E pop()
{
    list.remove(list.size()-1);
}
public E peek()
{

}

public boolean empty()
{
   if ( list.size()== 0)
   {
       return false;
   }
   else
   {
       return true;
   }
}

This is part of a driver code my teacher gave me in order to under stand the stack. I understand what each part of the stack does, I am just not understanding how to implement the stack based on this code. I need help with the peek method mainly, but if you see other issues please let me know. I would appreciate the help.

public E peek(){
  if(empty()) return null;

  int top = list.size()-1;
  return list.get(top);
}

AND empty method can be simplifized to:

public boolean empty(){
  return  list.size() == 0;
}

OR

public boolean empty(){
  return  list.isEmpty();
}

AND pop method should throws NoSuchElementException when stack is empty.

public E pop(){
  if(empty()) throw new NoSuchElementException();

  int top = list.size()-1;
  return list.remove(top);
}