Creating an Array of Objects in a Constructor

[Alan Flynn]

Hi all

I want to create a simple app that takes a name from the console then compares the name to a small phone book,when the name matches another name it will return the associated phone number.

I have a small contacts class which has name and number fields,Then I have a phone book class which populates an array with 4 contact objects that I can compare the entered number against.

here is my contacts class

public class Contact 

{
	String name;
        int number;


    //constructor to make new contact
    public Contact(String name, int number)
    {
        this.name = name;
        this.number = number;
    }

}

and here is my attempt at the phonebook class

public class PhoneBook
{
	
	public PhoneBook () 
    {
        Contact MaryJones = new Contact("Mary", 1800252525);
        Contact BobSmith = new Contact("Bob" , 1800343434);
        Contact MartinDunne = new Contact("Martin", 1800797979);
        Contact SarahMitchel = new Contact("Sarah", 1800898989);

       Contact[] contactList = new Contact[4];

        contactList[0] = MaryJones;
        contactList[1] = BobSmith;
        contactList[2] = MartinDunne;
        contactList[3] = SarahMitchel;

    }

    
    
    
    //variable to hold name entered
    String nameEntered;

   
    
    //method to look up name
    public String lookUpNumberByName(String name)
    {

        nameEntered = name;

        /**
         code to compare the name entered with the
         the names of the contact objects.
         If the name is a match with a contact name then return
         the associated number
         **/
       
        
        
        
        
        //return number
        return null; 
    }
		
	

	
	public static void main(String[] args) 
	{
		
		PhoneBook newBook = new PhoneBook();
		
		System.out.print (newBook.MaryJones.name);

	}

}

In the main method I am just trying to print out one of the fields for one contact to see if I can actually access it to compare it to the name entered.Its saying "MaryJones" cannot be resolved to a type.I'm guessing I cant create all that code in the constructor?Can anyone give me a hand on how it should look?
Thanks in advance

[Winston Gutkowski]

Alan Flynn wrote:Can anyone give me a hand on how it should look?

Sure. Try this as a start:

public class PhoneBook {
   Contact[] contactList = new Contact[4];

   public PhoneBook () {
        Contact MaryJones = new Contact("Mary", 1800252525);
        ...
}

(I'll leave you to fill in the rest)
I think you'll find that works a lot better.

Now, the question is why?

Perhaps you can tell us?

Winston

[Alan Flynn]

hi Winston Thanks for the quick reply!

I definitely want to try and fill it out myself!Its the only way I will learn

OK so from what I see you moved the creation of the contactList out of the Constructor?
Hmm..So does this mean the array will be created first then populated by the constructor after??

[Winston Gutkowski]

Alan Flynn wrote:OK so from what I see you moved the creation of the contactList out of the Constructor?
Hmm..So does this mean the array will be created first then populated by the constructor after??

No, it means that it is now part of the object; not part of the constructor. And that means that it can be accessed by any method IN the object.

You're worrying too much about mechanics at the moment.

Winston

[Ashley Bye]

Following on from that, can you think of a way to access the name of MaryJane without declaring and initialising the variable in the class scope? If you think about what you are doing in the constructor and the affect of the change Winston suggested I think you should be able to come up with the solution. Let us know how you get on.