How to use getter and setter for Custom classes with array and how to handle crash due to null during json parsing

Question

I am new to this one I need to parse json for Question and Answer Bank and set data in Custom ArrayList I unable to set the data using getter and setter.

My First Class

//Custom ArrayList
ArrayList<DataBO> dt=new  ArrayList<DataBO>();

//Class With Getter Setter

    public class DataBO
    {

        **public Questions[] Questions;**


        public String PointsCanBeEarnedMsg;

        public String ContentUrl;

        public String getPointsCanBeEarnedMsg ()
        {
            return PointsCanBeEarnedMsg;
        }

        public void setPointsCanBeEarnedMsg (String PointsCanBeEarnedMsg)
        {
            this.PointsCanBeEarnedMsg = PointsCanBeEarnedMsg;
        }

        public String getContentUrl ()
        {
            return ContentUrl;
        }

        public void setContentUrl (String ContentUrl)
        {
            this.ContentUrl = ContentUrl;
        }

        public Questions[] getQuestions ()
        {
            return Questions;
        }

        public void setQuestions (Questions[] Questions)
        {
            this.Questions = Questions;
        }


    }

2nd Class for Question Array

    public class Questions
    {
        public String CorrectOptionCount;

        public String QuestionId;

        public String QuestionString;

    public String getCorrectOptionCount ()
    {
        return CorrectOptionCount;
    }

    public void setCorrectOptionCount (String CorrectOptionCount)
    {
        this.CorrectOptionCount = CorrectOptionCount;
    }

    public String getQuestionId ()
    {
        return QuestionId;
    }

    public void setQuestionId (String QuestionId)
    {
        this.QuestionId = QuestionId;
    }

    public String getQuestionString ()
    {
        return QuestionString;
    }

    public void setQuestionString (String QuestionString)
    {
        this.QuestionString = QuestionString;
    }

    public Options[] getOptions ()
    {
        return Options;
    }


    }

These

Questions [] qs=new  Questions[len];
qs[i].setQuestionId(data);

are not working, getting NullPointer Exception??? How to add data in Questions after that in ArrayList??

Please use camel case for variable names. – Murat Karagöz May 26 '15 at 15:23 — Murat Karagöz, May 26 '15 at 15:23
Thanks @MuratK. for Suggestions. – ranjan Apr 17 '16 at 18:25 — ranjan, Apr 17 '16 at 18:25

score 3 · Answer 1 · answered May 26 '15 at 15:21

With this:

Questions [] qs=new  Questions[len];
qs[i].setQuestionId(data);

You just allocated space for array with default values i.e. null. You need to initialize every element like

//loop to initialize Questions which is held by array
qs[i] = new Questions();
...
qa[i].set..

score 1 · Accepted Answer · answered May 26 '15 at 15:24

Questions [] qs=new  Questions[len];
qs[i].setQuestionId(data);

With this code you're only creating an array of size len, but you aren't allocating each element. At this point the array looks like this:

{null, null, ..., null}

You need to fill the array with instances of Questions in a loop. An example code to do this would be

Questions [] qs=new  Questions[len];
for(int i = 0; i < len; i++)
    qs[i] = new Questions();

So that each element of the array is assigned a Questions instance. After you do this you are able to access each element as you did before.

How to use getter and setter for Custom classes with array and how to handle crash due to null during json parsing

2 Answers2