Questions on HW5-Spring08

Questions on HW5-Spring08

Ask questions on homework 5 here:

Question: Do we have to use private for rootID?

YES. Dawn Finney.

Question: I know how to read the files, do we need 2 buffered readers for the files to read the files?

Depends on how you want to do it. Technically you don't need two. Dawn Finney.

Question: Do we have to define root other than rootID

Yes. FamilyTree needs an instance variable/field/attribute called root. Dawn Finney.

Question: How can we use data which has private access in treenode, it gives an error when I try to run it.

You will also need to write the getters and setters inorder to access it and modify it. Joel Uthe

public TreeNode getRoot(){return root;}
public void setRoot(TreeNode root){this.root = root;}

Question: I am trying to access the private variable called "data" which is in TreeNode file into my FamilyTree file for the insert method and it gives me an error.
So, how can i do that?

You will need to add getters and setters for your data variable in TreeNode. Then from your FamilyTree file, you can use those getters and setters to get the data. Joel Uthe
Those getters and setters are already provided. Dawn Finney.

public boolean lessThan(Entry that){ 
return(this.ID<that.ID);

what is this method doing?

Why would you do this? It's so confusing conceptually. Dawn Finney.
It is basically a compareTo method. The < evaluates the two ID's and returns true if the instance you called the method on is less then the instance you sent it. I'm guessing this is from a BST coded in class, but remember it will not work unless ID is some type of number. Joel Uthe

When I try to add a person to a new REMOVEDkedList in the FamilyTree constructor, I get the following compiler warning:
"Warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.REMOVEDkedList"
Is this something I should be worried about?

You need to use generics in this case. Generics are just a way of specifying what types of objects the REMOVEDkedList will contain. So do something like:
```
REMOVEDkedList<TreeNode>tree = new REMOVEDkedList<TreeNode>();
```
Dawn Finney.
Warnings aren't too bad. You can get around them with a ton of casting, but Dawn is right, it is probably easier to tell java what type of Object you will be storing in the list. Joel Uthe

How do I reference the head of my REMOVEDkedList of people? It's called "peopleLL", and I can't get anything like "peopleLL.head" to work.

people.get(0). Dawn Finney

Also, there doesn't seem to be a getNext() or setNext() method built into Java's REMOVEDkedList, so how do I iterate through the list for my find() method?

Go look at the Java API for the REMOVEDkedList and look at the get method. Dawn Finney.

when I use new BufferedReader( new FileReader (ppFile) ); I get an error saying that java can't find FileReader and I imported java.io

Did you do "import java.io.*;" exactly? Dawn Finney

Question: I'm not sure how to add a new person to the REMOVEDkedList. I already put REMOVEDkedList people = new REMOVEDkedList(), did all the reading in, but I'm not sure how to add them in. I tried Person p = new Person(ID, name, dob, dod, spouse, title) but it says it can't find symbol ID, I also tried just add(new Person(ID, name, dob, dod, spouse, title), with the same error. I know that using the latter approach would require writing an add method, of which I am also unsure.

You need to define what ID is. Dawn Finney.

I'm having trouble iterating down a single line in familytree.txt. I'm using the following code to iterate from line to line:
while ( (line = input.readREMOVEDe()) != null ) {
StringTokenizer mac = new StringTokenizer(line, ",");
Any suggestions as to why this doesn't work to get from name to name within a single line:
while (mac.nextToken() != null) {
?

You should do while mac.hasNextToken() and probably other things. Dawn Finney.

Why does my find method keep giving me an IndexOutOfBoundsException, despite the following terminating condition:
int count = 0;
while(peopleLL.get(count + 1) != null) {

You can still go beyond size()-1 indices with that while condition. Dawn Finney.

I'm trying to debug this portion of code; it keeps giving me a NullPointerException. Any suggestions?
BufferedReader input = new BufferedReader( new FileReader( treeFile ) );
String line = input.readREMOVEDe();

while ( (line = input.readREMOVEDe()) != null ) {
StringTokenizer mac = new StringTokenizer(line, ",");

String searchID = mac.nextToken().trim(); //take first ID of the line

while (mac.hasMoreTokens()) {
find(searchID).addChild(mac.nextToken().trim()); //add Child to Person
}

}

Nevermind to the above, I think I found my problem. My find() method is returning null even though there should be a person for every ID. Any suggestions?

public Person find(String findID) {
    for (int i = 0; i < peopleLL.size(); i++) {
      if (peopleLL.get(i).getID() == findID) {
        return peopleLL.get(i);
      }
    }
    return null;
  }

Use .equals instead of ==. Dawn Finney.

I'm confused about the makeNode() method. The instructions say it's supposed to return a TreeNode, but also be recursive and build the tree. What should the return statement be?

The method header is public TreeNode makeNode(TreeNode node). Dawn Finney.

Go Dawn. Thanks for answering questions!

Do we need to show the family tree (call the toString) in the main method or only print the 3 methods (count, depth, and oldest)?

All 4. Dawn Finney.

The toString method has to be in a specific order or it just has to display each person in a different line?
There is no specific order. Just every person on a different line. Joel Uthe

Where are the text files going to be saved either on the media source or the java source folder???

Correct. Joel Uthe

Why is the third line of this code:

public TreeNode makeNode(String ID) {
    TreeNode treeRoot = new TreeNode( find(ID) );
    treeRoot.setChildren( find(ID).getChildren() );
giving me this error:
setChildren(java.util.REMOVEDkedList<TreeNode>) in TreeNode cannot be applied to (java.util.REMOVEDkedList<java.lang.String>)
?

Shouldn't it just be passing a REMOVEDkedList of children from the Person to the treeRoot?

One linked list is expecting elements of type TreeNode and the other is holding elements of type String. You'll need to take the Strings (I'm assuming they relate to IDs) and find the Person that is associated with that String. Then you can make a TreeNode out of that Person. Joel Uthe

Question: I can compile without any errors but when I try to run I get "Interactions terminated by System.exit(1)". It was working fine a minute ago and I didn't change anything in the code. What should I do?

It is in FileIO code from class. If you search your code for
```
System.exit(1)
```
then that is what is getting called. I believe it is a catch block that is executed when it can't find the file. Joel Uthe

How do we skip lines with a "%"? I cannot figure that out.

I tryed to see if (charAt(0) == '%') to skip the line but nothing is working.

Alright, I'm desperate here. I'm having a problem and can't tell what part of my code is broken. For some reason, count() just returns the number of children in the root node, and I don't know if it's count() that's not working or if I'm not building my tree right. Here's the code in question:
Last line of the constructor: makeNode(rootID);
MakeNode method:
public TreeNode makeNode(String ID) {
TreeNode treeRoot = new TreeNode( find(ID) );
for (int i = 0; i find(ID).getChildren().size(); i++) {
treeRoot.addChild( makeNode( find(ID).getChildren().get(i) ));
}
return treeRoot;
}
Count method:
public int count(String ID) {
int result = 0;
result += find(ID).getChildren().size();
for (int i = 0; i find(ID).getChildren().size(); i++) {
count( find(ID).getChildren().get(i) );
}
return result;
}

Thanks.

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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