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Thread: Creating an exact replica of an original instance?

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    Default Creating an exact replica of an original instance?

    Hi guys,
    I'm working on a homework set. Here is the question I am having trouble with.

    Suppose that you want to make a copy of a City instance. This can be done with a public constructor that takes a City instance as a parameter, and makes an exact replica of the orginal instance. It constructs this copy using getName and getPopulation methods.

    The new City instance should have the same name and population values as the City instance that is passed to the constructor as a parameter. The City object that is passed as a parameter should not be modified.

    Here is my code so far:
    public class City {
     
      private String name;
      private int population;
     
      public String getName () {
        return name;
      }
     
      public int getPopulation () {
        return population;
      }
     
      public Object copy(City) {
         return new City(getName(), getPopulation());
    }

    Am I even using the right method? How do I write this?

    Thanks in advance.


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    Super Moderator Norm's Avatar
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    Default Re: Creating an exact replica of an original instance?

    done with a public constructor that takes a City instance as a parameter
    Where is the constructor that takes a City object as a parameter?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Creating an exact replica of an original instance?

      public Object copy(City) {
         return new City(getName(), getPopulation());
    }

    well I think that's what I'm trying to create here.

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    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Creating an exact replica of an original instance?

    So now I have:
    public cityCopy(City){
    name=getName();
    population=getPopulation();
    }

    and it's still wrong.

    It keeps telling me I need a return type. But it's a constructor...

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    Default Re: Creating an exact replica of an original instance?

    Why do you think its a constructor? Read the doc at the link I gave.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Creating an exact replica of an original instance?

    I didn't ignore your answer. A constructor is what creates a new object in a certain class. It defines it's parameters so when they are given a value, you know which object it belongs to. I wrote my constructor for cityCopy which takes a City as a parameter and uses the getName and getPopulation methods to copy the attributes from the original city.

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    Default Re: Creating an exact replica of an original instance?

    I wrote my constructor for cityCopy
    From the tutorial:
    Constructor declarations look like method declarations—except that they use the name of the class and have no return type.
    If you don't understand my answer, don't ignore it, ask a question.

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