Implementation of Generic Binary Tree Code

Question

I'm in the process of independently learning Generics as a way to build on a college assignment for Binary Search Tree. I've completed this program without Generics first and now I've converted over but I wanted to get some peer review. It seems to be working well and I've run a few tests already.

Would you do anything differently and why?

My main():

public class Assign3 {

    public static void main(String[] args){

        String choice = new String();

        Scanner in = new Scanner(System.in);

        Contact newContact;

        BinaryTree<Contact> tree = new BinaryTree<Contact>();


        while(!choice.equals("7") ){
            System.out.println("\nPlease select option:\n1: Display the Tree\n2: Add to the List\n3: Add from a File\n4: Save to a File\n5: Determine if a Person is in the List\n6: List out who calls whom\n7: To Exit");
            choice = in.next(); in.nextLine();
            switch(choice){
            case "1": 
                tree.displayInOrder();
                break;
            case "2":
                newContact  = new Contact();
                if(newContact.addContact(in, false))
                    tree.insertInTree(newContact);
                break;
            case "3":
                System.out.println("Enter name of file to write to: ");
                Scanner f = readFile(in.next());
                if(f!=null){
                    while(f.hasNext())  {
                        newContact = new Contact();
                        if(newContact.addContact(f, true))
                            tree.insertInTree(newContact);
                        else System.out.println("Unable to add contact from file. Proceeding to next contact..");
                    }
                    f.close();
                }
                break;
            case "4": 
                System.out.println("Specify a filename to save: ");
                FileWriter o = writeFile(in.next());
                if(o != null)
                    writeToFile(o, tree.root);
                try {
                    o.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                break;
            case "5":
                newContact = new Contact();
                if(newContact.addContact(in, false))
                    tree.searchTree(newContact);
                break;
            case "6":

                if(tree.root != null)
                    callWhom(tree.root);                
                break;
            case "7":   
                System.out.println("Exiting…");
                break;
            default:    
                System.out.println("Invalid input... please try again.");
                break;
            }
        }
    }

    public static Scanner readFile(String fileName){
        File file = new File(fileName);
        Scanner rF = null;

        try {
            rF = new Scanner(file);
            return rF;
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            System.out.println("File does not exist..");
            return null;
        }
    }

    public static FileWriter writeFile(String fileName){
        FileWriter wF = null;

        try {
            wF = new FileWriter(fileName);
            return wF;
        } catch (IOException e) {
            // TODO Auto-generated catch block
            System.out.println("Unable to write file..");
            return null;            
        }       
    }

    public static void callWhom(BinaryTreeNode<Contact> subRoot){
        System.out.print(subRoot.getData().getName() + " calls ");
        if(subRoot.getLeft() != null){
            System.out.print(subRoot.getLeft().getData().getName());
            if(subRoot.getRight() != null)
                System.out.println(" and " + subRoot.getRight().getData().getName());
            else
                System.out.println();
        }
        else if(subRoot.getRight() != null)
            System.out.println(subRoot.getRight().getData().getName());
        else
            System.out.println("No Contact");

        if(subRoot.getLeft() != null)
            callWhom(subRoot.getLeft());

        if(subRoot.getRight() != null)
            callWhom(subRoot.getRight());
    }

    public static void writeToFile(FileWriter o, BinaryTreeNode<Contact> subRoot){

        try {
            if(subRoot.getLeft() != null)
                writeToFile (o, subRoot.getLeft());
            o.append(subRoot.getData().getName() + "\n" + subRoot.getData().getPhone() + "\n");
            if(subRoot.getRight() != null)
                writeToFile (o, subRoot.getRight());            


        } catch (IOException e) {
            // TODO Auto-generated catch block

        }
    }
}

My BT class:

public class BinaryTree<F extends Comparable<F>> {

    BinaryTreeNode<F> root = null;

    public boolean insertInTree (F data) {

        BinaryTreeNode<F> item = new BinaryTreeNode<F>(data);

        if (root == null) 
            root = item;
        else 
            return root.insert(data);
        return true;
    }

    public void displayInOrder () {
        System.out.println("Phone List");
        if (root == null){  
            System.out.println("List is Empty");
            return;
        }
        else
            displayInOrder (root);
    }

    private void displayInOrder (BinaryTreeNode<F> subRoot){
        if(subRoot.getLeft() != null)
            displayInOrder (subRoot.getLeft());
        System.out.println(subRoot.getData() + " ");
        if(subRoot.getRight() != null)
            displayInOrder (subRoot.getRight());
    }

    public boolean searchTree(F temp){

        if (root == null)
            return false;
        else
            return root.search(temp);
    }
}

My Node class:

public class BinaryTreeNode<F extends Comparable<F>> {

    private F data;

    private BinaryTreeNode<F> left, right;

    public BinaryTreeNode() {
        this(null);
    }

    public BinaryTreeNode(F data) {
        left = null;   
        right = null; 
        this.data = data;
    }

    public F getData() {
        return data;
    }

    public void setValue(F value) {
        this.data = value;
    }

    public BinaryTreeNode<F> getLeft() {
        return left;
    }

     public void setLeft(BinaryTreeNode<F> left) {
            this.left = left;
        }

    public BinaryTreeNode<F> getRight() {
        return right;
    }

     public void setRight(BinaryTreeNode<F> right) {
            this.right = right;
        }

    public boolean insert (F newData) {

        if (data.compareTo(newData)  <  0) {
            if (left == null){
                left = new BinaryTreeNode<F>(newData);
                return true;
            }
            else 
                return left.insert(newData);
        } else if (this.data.compareTo(newData)  >  0) {
            if (this.right == null){
                this.right = new BinaryTreeNode<F>(newData);
                return true;
            }
            else 
                return right.insert(newData);
        } else 
            System.out.println("Duplicate - not adding " + newData);
        return false;
    }

    public boolean search(F findData){

        if(data.compareTo(findData) < 0){
            if(left == null){
                System.out.println("Contact not in List");
            }
            else
                left.search(findData);
        }
        else if(data.compareTo(findData) > 0){
            if(right == null)
                System.out.println("Contact not in List");
            else
                right.search(findData);
        }
        else{
            System.out.println("Contact found in List");
            return true;
        }
        return false;
    }
}

My Contact class:

public class Contact implements Comparable<Contact>  {

    private String phone;

    private String name;

    public Contact(){
        phone = null;
        name  = null;
    }

    /**
     * Reads a valid date from the input provided
     * @param in Specifies the input to retrieve the date from
     * @param fromFile Boolean to notify the method if data is being read from a file
     * @return <code>true</code> if the method succeeds, <code>false</code> otherwise
     */
    public boolean addContact(Scanner in, boolean fromFile){

        if(!fromFile)
            System.out.print("Enter name of contact: ");
        if(in.hasNextLine()){       
            name = in.nextLine();
        }

        if(!fromFile)
            System.out.print("Enter phone number for contact: ");
        if(in.hasNextLine()){
            phone = in.nextLine();
            while(!Pattern.matches("^(\\d{1})?[\\(-]??\\d{3}\\)?[\\s-]?\\d{3}[\\s-]?\\d{4}$", phone) && !fromFile){
                System.out.println("Invalid number, please try again.. Example: 613-333-3333, 1(613)333-3333, 6133333333, (613) 444 5555");
                phone = in.nextLine();
            }
            if(!Pattern.matches("^(\\d{1})?[\\(-]??\\d{3}\\)?[\\s-]?\\d{3}[\\s-]?\\d{4}$", phone) && fromFile){
                System.out.println("Invalid telephone number");
                return false;
            }


            phone = phone.replaceAll("[\\D]", "");
            if(phone.length() == 10)
                phone = phone.replaceFirst("(\\d{3})(\\d{3})(\\d{4})", "1-$1-$2-$3");
            else if(phone.length() == 11)
                phone = phone.replaceFirst("(\\d{1})(\\d{3})(\\d{3})(\\d{4})", "$1-$2-$3-$4");
        }
        return true;
    }

    /**
     * Prints the contact name and phone
     * @return String that represents the contact stored in this object.
     */
    public String toString(){
        return name + ": " + phone;
    }

    /**
     * The method compares the Contact name. If the names are the same, the phone numbers are compared.
     * @return int value representing the comparison between two object's attribute (==0 means the objects attribute are the same)
     */
    @Override
    public int compareTo(Contact o) {
        // TODO Auto-generated method stub
        if(o.name.toUpperCase().compareTo(this.name.toUpperCase()) == 0){
            return o.phone.toUpperCase().compareTo(this.phone.toUpperCase());
        }
        return o.name.toUpperCase().compareTo(this.name.toUpperCase());
    } 

    /**
     * The function is used to retrieve the Contact name.
     * @return String that represents the Contact name
     */
    public String getName(){
        return name;
    }

    /**
     * The function is used to retrieve the Contact phone number.
     * @return String that represents the Contact phone number
     */
    public String getPhone() {
        // TODO Auto-generated method stub
        return phone;
    }
}

I'm a student and welcome all feedback but please give details.

Sharon Ben Asher · Accepted Answer · 2019-07-22 06:54:06Z

Here are my comments:

Apply the Visitor Design Pattern

There are several methods that perform similar process: recursively traverse the tree, and perform specific action on each node. (insert(), search(), write to file(), etc) this is a good fit for the visitor design pattern. In short, this pattern defines how you can implement the traversal of the tree in one place, and have it work with multiple operations on individual nodes.

Observe the Single Responsibility Principle

addContact() in the Contact class is responsible for getting a contact from user input from the console, or read a contact from a file. it further carries some elaborate and fairly complex validation rules. now what will happen when you want to read a contact from a database? or have a nice html form for user input? what if you wish to support foreign telephone numbers, where the placement of a dash can vary?

Avoid literals (a.k.a magic numbers)

while we are on the subject of telephone number validation: I do not know exactly why, but regex that validates telephone number is specified twice. now imagine that you find a bug in the regex. it is possible you will fix it in one place and forget to fix in the other. the principal also applies to user choice menu, what if you wish to add another choice? will you keep the ordering? what if you wish to change the choices from numbers to letters "a" through "f"?

`Comparable` and `Comparator`

When if you will want to store objects that are not Comparable in your spiffy binary tree? what if you will want to give the user an option of choosing whether the contacts will be sorted by number first, then by name? or perhaps the user wil have favorite contacts that will want to sort out first? for this wealth of options to be supported, you will want to have an overloaded insert() and search() that accept a comparator. this is analogous to the JDK Collections.sort() having an overloaded option that accepts a comparator.

lastly,

Observe naming conventions

The Java collections (your tree can be regarded as a collection) are parameterized with the generic T that is short for Type. The Map collection is parameterized with K and V . why did you choose F as the generic symbol? it is confusing for the programmer who is aware of the naming conventions. observing these conventions establishes a common language between Java developers and helps communication between them.

I'll do a little more research on the feedbacks and tackle it 1 at a time. For "Observe naming conventions" - honestly, I just failed to consider the next person trying to read my code and randomly selected F. I agree that it can be confusing to anyone familiar with the naming convention. It's good feedback and something I should consider, specially when I start working. — suMmGuy
– suMmGuy, Commented Jul 22, 2019 at 19:55
" Avoid literals (a.k.a magic numbers) " I see what you mean. In terms of the regex, there's really no need to have in there twice. A simple if condition (if reading data from a file) in the loop would allow me to break out of the loop in case of bad data in the file. No point in writing additional lines. — suMmGuy
– suMmGuy, Commented Jul 22, 2019 at 21:06
@suMmGuy, if you find the answer useful, you are welcome to accept and/or upvote — Sharon Ben Asher
– Sharon Ben Asher, Commented Jul 23, 2019 at 6:29

Stack Exchange Network

Implementation of Generic Binary Tree Code

1 Answer 1

Apply the Visitor Design Pattern

Observe the Single Responsibility Principle

Avoid literals (a.k.a magic numbers)

`Comparable` and `Comparator`

Observe naming conventions

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Hot Network Questions

Implementation of Generic Binary Tree Code

1 Answer 1

Apply the Visitor Design Pattern

Observe the Single Responsibility Principle

Avoid literals (a.k.a magic numbers)

Comparable and Comparator

Observe naming conventions

You must log in to answer this question.

Related

Hot Network Questions

`Comparable` and `Comparator`