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Thread: Issue with initialising Array

  1. #1
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    Post Issue with initialising Array

    I've created an array of a self defined object 'Team'... but when I try to set a property using the array I get a NullPointerException.. Research shows this is because the Array needs to be initialised though I can't see what more I need to do.

    I am using a Method of my new object but that doesn't seem to be the problem - as you will see I am declaring another instance of my object and I can use the Method fine on that 'myTeam' . I get the exception from the line where I am using the Method on Array (index 3)

     
           team[] teams = new team[40];
            team myTeam = new team();
     
            try {
                myTeam.setName("WBA");
                teams[3].setName("QPR");
            } catch (
                       Exception e) {
            System.out.println("Error : " + e);
            e.printStackTrace();
        }
     
     
    public class team {
     
        private String teamName;
     
     
     public void setName(String name) {
         teamName = name;
     
       }
     
    }

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    Default Re: Issue with initialising Array

    I get a NullPointerException
    Declaring an array of objects creates the structure with slots for instances of the class, but does NOT create the instances which means all the slots in the array have null values. You need to create instances of the class and assign them to the slots in the array.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Issue with initialising Array

    Thanks

    I interpreted your comment as a need for code like this

                 for(i=0;i<40;i++)
                teams[i] = new team();

    This is what I have inserted and I'm not getting the error now; Is this the recognised way of doing this?

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    Default Re: Issue with initialising Array

    Yes, that is a way to fill in an array, except use the array's length attribute not a hardcoded value like 40.

    My question about the code is why is it using an array instead of some Java collection like a List or Map?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Issue with initialising Array

    Probably because I'm a recent immigrant to Javaland from other languages, so not yet practiced in reaching for other constructs

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