Questions on HW3-Spring08

Questions on HW3-Spring08

Ask Questions on HW3 here:

Question: So why can't I open the HW3 java file?

We didn't give you a java file? I zipped up the javadoc folder. All you have to do is unzip it and click on ContactNode.html, ContactEntry.html, or ContactList.html to open the javadoc for the respective class. Dawn Finney.
It is also archived in .rar format (which I believe Winzip and most other archive utilities can handle). But if not then you can get a trial version (which has full functionality) here. Joel Uthe

Question: I am so confused on this homework, I don't know where to start. Can someone go over it in class Wednesday, please.

I agree with the above. I have a general outline of what each program should have in it from the instructions, but have no clue where to go from there. Recitation wasnt much help in putting all the three together. I dont know how we are supposed to know how to write these programs. The linked list guides dont go over enough of how to write the programs nor does the book.

We did (or should've) gone over how to write and start each of the classes necessary for the homework. If you are still confused you should seek out help via office hours, email, IM or this questions page. The getters and setters (accessors and modifiers) are completely standard. Once you know how to do one you know how to do all of them. The toString methods you have all ready seen before so you should know how to write one. Dawn Finney.

Question: Do the constructors in ContactEntry need to reference this.name, this.phone, etc or is "this" already implied?

You need this. Dawn Finney.

Questions: When I try to "return name" in my getName method in ContactEntry, the compiler can't find the variable "name." My variables are defined in both of my constructors, do I need to do it somewhere else as well?

Your variable should be declared in outside of the constructor, but initialized within the constructor. Thus something like:

public class ContactEntry{
   private String name; //name is declared here
   ...
   
   public ContactEntry(){
      name = null; //name is initialized here
      ...
   }

   public ContactEntry(String name, String phone, String email){
      this.name = name; //name is initialized here
      ...
   }
}

Where ... indicates that more code is necessary. Dawn Finney.

Question: What's the best way to do the toString method for ContactNode? Should I just extend ContactEntry and use its get() methods, or find a way to return a string from "data" in ContactNode?

Unless explicitly stated (like public class Turtle extends SimpleTurtle) all classes extend from Object and thus you get the toString() method from Object. However we want you to rewrite (override) this method so that toString will print out the data in the node. So inside the toString() method for ContactNode you can just call the toString method for the ContactEntry. Dawn Finney.
Oh and also STOP EXTENDING. You do not need to extend a class to use its method. Seriously stop that. Dawn Finney.

Question: For the methods in ContactList that return a boolean, what should I use as my criteria to determine if the method was successful?

Basically the boolean method will return true if the method successfully did what it was intended to do. If the insertAfter method actually inserts a new node into the list then the insertAfter method will return true. For the delete method, if we actually found and removed the node we wanted to delete then the method will return true. Dawn Finney.

Question: I'm not sure if this is only temporary, but I can't get the montage.java and TAPicture.java to come up in the code archive of t-square.

I honestly have no idea what you are talking about. This is not the place to ask that question. Dawn Finney.

Question: Back to methods that return a boolean - so I don't even have to include a return statement in the method, it just does everything automatically?

No nothing is done automatically. I described the conditions on which it would return true. You have to actually write "return true;" somewhere in your code and also "return false;" somewhere. Dawn Finney.

Question: What that person was probably referring to was that on Prof. REMOVED's prism account, the montage.java file is "Forbidden". I was looking for example help on the hw... because I know he uses some of the methods in his montage.java example... but his files aren't public or something.

Then you should ask him directly. Professor REMOVED wouldn't touch the coweb with a ten foot pole. Dawn Finney.

Question: When I try to compile code with public setName (String name), I get an error saying that I need a return type. What return type do I need?

The signature of every method is visibility returnType methodName(params)...So public returnType setName(String name)...you don't need to return anything, so what should your return type be? Hint: starts with a v.. Joel Uthe

Question: If I wanted to see if the next node is equal to "node1", how would I do it? "if (getNext().equals(node1)) {}" doesn't work; is there something similar that does? This is for the delete() method, and I'm trying to set the current node's "next" to the next node's "next".

getNext().equals(node1)) is a way to do it...it is how I would do it. But it depends on how you have written the rest of your code. I would liberally use System.out.println to debug your program and seeing if what you think should be happening is actually happening. Joel Uthe
getNext() needs to be called a ContactNode for one thing. Dawn Finney.

Question: Are we supposed to be providing actual names and phone numbers, like he provided in the TA montage example?

No. You will need to input real data to test your methods in some main method, but otherwise no. Dawn Finney.

Question: Could you explain how to create real data to test the methods?

You know how to write a main method and test methods. Create ContactEntries, ContactNodes and a ContactList and test your methods. Dawn Finney.

Question: How can you address a name or number field in a ContactNode for the search method in ContactList? I can't figure out how to go from node to data to ContactEntry, and access the strings.

You get the data(a ContactEntry) from ContactNode and then get the name, phone or email from there. Dawn Finney.

Question: For the delete( node ) method, I dont understand the theory behind it. If you are given a node to delete, wouldnt you have to know the node before that one too so you can set the before node.next = node.next?

Yep. So how would you modify your loop so that you find the node before the one you want to remove? Dawn Finney.

Question: In ContactEntry, for setName(String name) do we write this.name = name or String name = ""?

The first one. Dawn Finney.

Question: For the toString method in ContactList, should the method build an array of strings and return that, or is there a more elegant way to do it?

Not an array, but a bigger and bigger String as you concatenate on the String from each node. Dawn Finney

In the add() method of ContactList, the following statement keeps giving me a list of NullPointerExceptions:

if (head.equals(null)) {head = contactToInsert;}
Any suggestions?|

Do head == null. Dawn Finney.

In ContactNode, do we use the word data as the variable?

It's technically a field. Dawn Finney.

On the extra credit portion when you ask to sort by name, phone and email do you mean to put them in alphabetical order or just display them in terms of their section section? Because if it were to be in alphabetical order how would I be able to do that with the phone numbers considering they are numbers?

123...for phone it would be numerical order. And yes, you are expected to actually rearrange the list. Joel Uthe

What is the difference between "while (current.getNext() != null)" and "while(current != null)"?

One tests if we are past the end of the list and the other tests if we are at the end of the list. It is an important difference for different methods. Delete will probably want to test current.getNext(). Joel Uthe

On the insertAfter and delete methods, are we supposed to have it return true and false?

In ContactList, are we supposed to be coding a new LinkedList?

I need help with the searchByName. You start with String name = name, right? Then what?

For the fourth above question, which one should you use for insertAfter?

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Homeworks-Spring 2008 last edited on 14 April 2008 at 11:35 am by lawn-128-61-18-61.lawn.gatech.edu