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channahnaiman/ Secret

Last active Jun 27, 2018
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COMP 271 Lab 4

Team project

Work in teams of two but run individual JShell sessions and submit individually (see details below)


An understanding of the following concepts and techniques:

  • ADT implementation perspective
  • dynamically allocated objects
  • linked lists
  • navigating through linked lists
  • iterators


In this lab, you will have the opportunity to look "under the hood" of linked lists by creating and manipulating nodes. You will do this interactively using the JShell that comes with Java 9.

  1. If using c9, remove Java 8 from your workspace:

     sudo apt remove -y oracle-java8-*
     sudo apt-get autoremove
  2. Install Java 9:

    This is a fairly big download, so it might take a while.

  3. Start the JShell like so:

    jshell -R-ea

    If this does not work, double-check your Java 9 installation.

  4. Define this generic node class:

    class Node<E> {
      public E data;
      public Node<E> next;
      public Node(final E data, final Node<E> next) { 
        if (data == null) throw new IllegalArgumentException("data is null"); = data; = next; 
      public Node(final E data) { this(data, null); }
      public String toString() { 
        return "Node@" + hashCode() + "(" + data + 
          (next != null ? ", Node@" + next.hashCode() + ")" : ")"); 

    Hint: If you make a mistake in a class or method definition, don't worry. You can just reenter it to replace the erroneous or incomplete definition.

  5. Question: What is the purpose of E in this class definition?

  6. Question: What is the purpose of this in the second constructor definition?

  7. Question: What is the purpose of toString in this class definition?

  8. Create a linked list of nodes containing the strings "hello", "<YOUR NAME>", "what", and "up". Use as many statements as you want.

    Hint: To create a single node, use new Node<>("abcd"). The <> notation is a placeholder for the specific E the system infers for you, in this case, String.

    Hint: It is best to define named variables for your various objects instead of relying on the auto-generated $... names.

  9. Now create the same list using a single statement.

  10. Question: Which way to create the list more clearly conveys the actual structure of the list?

  11. Define a method for printing the items in a linked list, starting with the head (first) node:

    <E> void printNode(Node<E> curr) { ... }

    Hint: Iterate through the list until curr becomes null.

    Hint: In case your method invocation (or any other code) goes into an infinite loop, you can interrupt execution by pressing Control-c.

  12. Remove the node containing "what" from your list above. Use printNode to verify that the node is gone from the list.

  13. Add the node containing "what" back but at the very end of the list. Use printNode to verify that the node is now in the correct position.

  14. Now create a circular list by making the successor of the list refer back to the head of the list.

  15. Question: What happens if you use the printNode method on this circular list?

  16. Define an enhanced printNodeCycle that works like printNode but stops the iteration when it detects a cycle in the list.

  17. Invoke printNodeCycle on your circular list.

  18. Question: How would you describe the shape of any noncyclical structure you can build using the Node class? Furthermore, can you build structures with branches that look like trees, where a node can have more than one successor or neighbor?

  19. Write the equivalent of printNode using an Iterator over a java.util.LinkedList?

    final List<String> myList = new LinkedList<>(Arrays.asList("hello", "<YOUR NAME>", "what", "up"));
    final Iterator i = myList.iterator();
    // TODO while loop using i.hasNext() and
  20. Question: Would the same code work for an ArrayList?

Deliverables and submission

Please submit the following deliverables:

  • Individual Sakai submission under "Lab 4":
    • gist with JShell history and Written part (see below for details)
    • brief description of your collaboration style and summary of your individual contributions to this team project


  • 8 submission of both deliverables as part of a single secret gist - be sure to submit this gist's URL through Sakai
  • 20 JShell history (jshell> /save -history myhistory.jsh) showing the steps described above (it's OK if errors are included)
  • 12 written part

40 points TOTAL


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