Implementing LinkedList as a user?

Hello JPF! I have just been introduced to LinkedList and I am working on my first programming assignment, but I am really confused and lost. My professor wants us to implement the program as a user; I am unsure what she means, so can anyone please explain this? Because I have just been introduced to LL, I am just playing around with it, and so far, I haven't been able to get anything to work.

I'm not writing any particular program at the moment, but I haven't been able to get the code below to print out right; I've been getting an error because there's something wrong with my insert method, but I do not know what. Can someone please tell me what I'm doing wrong?

Code :

---

import java.util.LinkedList;
 
public class Editor
{
 
   private LinkedList<String> text;
 
   public String display()
   {
      return text.getFirst() + "\n" + text.getLast();
   }
 
 
   public void insert(String s)
   {
      text.add(s);
   }
 
}

---

Code :

---

public class Tester
{ 
   public static void main (String [] args)
  {  
      Editor e = new Editor();
      e.insert("test1");
      e.insert("test2");
      e.insert("test3");
      System.out.println(e.display());
  }
 
}

---

Hello,

First thing I noticed when I tried to run your code was a nullpointerexception on the variable text.

You need to actually initialise/create the linked list.

Code :

---

private LinkedList<String> text = new LinkedList<String>();

---

After that, everything worked just fine for me. For more information on the LinkedList have a look at LinkedList (Java Platform SE 6)

// Json

Thank you, Json!

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Cheers!

// Json