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Thread: No idea what to do for this

  1. #1
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    Default No idea what to do for this

    Here is the prompt I got-
    The code below shows some of the text for a class called City. As you can see, a City has two instance variables, name and population. Write a complete public constructor (including header line) with no parameters, which sets the population to an initial value of -1, and the name to an initial value of "unknown".

    public class City {
     
      private String name;
      private int population;

    thats all i know haha


  2. #2
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    Default Re: No idea what to do for this

    I believe what you're being asked to do is something like this:

    public City(String _name, int _population)
    {
    population = _population;
    name = _name;
    }

    And then create a "City":

    City NewCity = new City("New York", 100);

    See how I use the constructors I created in making a new "City"?
    I'm a beginner but I'm pretty sure that's right.

  3. #3
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    Default Re: No idea what to do for this

    Then what is the actual answer? because all i have so far is

    public class City {
     
      private String name;
      private int population;

    so im not sure what follows it

  4. #4
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    Default Re: No idea what to do for this

    It would be:

    public class City {
    public static void main(String args[]){
      private String name;
      private int population;
      public City(String _name, int _population)
     {
        population = _population;
        name = _name;
     }
    City NewCity = new City("New York", 100);
    }
    }

  5. #5
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    Default Re: No idea what to do for this

    Yeah, that didn't work.

    I tried substituting "unknown" for "New York" and -1 for 100 because thats what the prompt said but that didnt work either

  6. #6
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    Default Re: No idea what to do for this

    I figured it out.

    public City()
    {
    name = "unknown";
    population = -1;
    }
    is what has to be put in

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    Default Re: No idea what to do for this

    Uhmmmm, that's not a constructor method but sure that will work, I didn't realize you wanted it that simple lol.

  8. #8
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    Default Re: No idea what to do for this

    That is a constructor. It's what's known as a "default constructor", i.e. it intializes all the values to some pre-determined initial value, in this case -1 and "unknown".

    As a second note, if you are going to be providing other constructors that create an initial value (say, a constructor which also sets the city name), I would recommend calling that constructor from the the default constructor. This reduces the amount of code you have to check for problems.

    public City()
    {
        // call the other constructor that actually assigns values
        this("unknown", -1);
    }
     
    public City(String name, int population)
    {
        this.name = name;
        this.population = population;
    }
    Last edited by helloworld922; July 18th, 2010 at 08:19 PM.

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