Exception in thread "main" java.lang.NullPointerException1000

Question

public class Employees {
    private String[] onomata,eponyma;
    private int[] kwdikoi;
    private int i,kwdikos;
    private String onoma,eponymo;
    private long kwdikoslong;

    {
        FileReader reader = null;

    try {
        reader= new FileReader("employees.json");
        } catch (FileNotFoundException e1) {
            e1.printStackTrace();
        }
    JSONParser jsonparser= new JSONParser();

    try {
        JSONObject jsonobj = (JSONObject) jsonparser.parse(reader); 
        JSONArray baseArray =(JSONArray) jsonobj.get("employees");

        for (int i=0;i<baseArray.size();i++) 
        {
            JSONObject jsonobj2 = (JSONObject) baseArray.get(i);
            onoma=(String) jsonobj2.get("onoma");
            onomata[i]=onoma;
            eponymo=(String) jsonobj2.get("eponymo");
            eponyma[i]=eponymo;
            kwdikoslong=(long) jsonobj2.get("kwdikos");
            kwdikos=(int)kwdikoslong;
            kwdikoi[i]=kwdikos;
        }
    }
    catch (IOException e) {
        e.printStackTrace();
    } catch (ParseException e) {
        e.printStackTrace();
    }

After getting a `FileNotFoundException` do you think it is wise to continue? — Scary Wombat, Apr 30 '20 at 00:48
here is the employees.json file { "employees": [ {"onoma":"Kyriakos","eponymo":"Theodoridis","kwdikos":3511}, {"onoma":"Dimitris","eponymo":"Soukos","kwdikos":3522}, {"onoma":"Tasos","eponymo":"Gkortsopoulos","kwdikos":3533}, {"onoma":"Aggelos","eponymo":"Gogos","kwdikos":3544}, {"onoma":"Giorgos","eponymo":"Mpoulari","kwdikos":3555}, {"onoma":"Aris","eponymo":"Gouri","kwdikos":3566}, {"onoma":"Giorgos","eponymo":"Georgis","kwdikos":3577}, {"onoma":"Panos","eponymo":"Vadiakas","kwdikos":3588}, {"onoma":"Aggelos","eponymo":"Babis","kwdikos":3599}, ] } — kyriakos, Apr 30 '20 at 00:54
Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Mad Physicist, Apr 30 '20 at 00:55
You need to edit the question and put the new information there. Not in comments. — Harshal Parekh, Apr 30 '20 at 00:55
I keep getting this : Exception in thread "main" java.lang.NullPointerException at project2.Employees.(Employees.java:37) — kyriakos, Apr 30 '20 at 00:55
`private String[] onomata,eponyma;` declares the variables, but they are still null. Why not use an ArrayList instead? — Scary Wombat, Apr 30 '20 at 01:20

Harshal Parekh · Accepted Answer · 2020-04-30T01:39:59.910

Your problem is here:

private String[] onomata, eponyma;

The variable onomata is never initialized.

try {
    JSONObject jsonobj = (JSONObject) jsonparser.parse(reader); 
    JSONArray baseArray =(JSONArray) jsonobj.get("employees");

    // initialize it here
    onomata = new String[baseArray.size()];

    for (int i = 0; i< baseArray.size(); i++) 
    {
        JSONObject jsonobj2 = (JSONObject) baseArray.get(i);
        onoma=(String) jsonobj2.get("onoma");
        onomata[i]=onoma;
        eponymo=(String) jsonobj2.get("eponymo");
        eponyma[i]=eponymo;
        kwdikoslong=(long) jsonobj2.get("kwdikos");
        kwdikos=(int)kwdikoslong;
        kwdikoi[i]=kwdikos;
    }
}
catch (IOException e) {
    e.printStackTrace();
} catch (ParseException e) {
    e.printStackTrace();
}

This will not fix all the exceptions. As and when you encounter them, start initializing the arrays and fix them.

Side notes:

From here, you should not continue your code when a FileNotFoundException occurs.

It is better to do this:

jsonobj2.getString("onoma", "DEFAULT");
// than this: (String) jsonobj2.get("onoma")

This is the generic solution to all the NullPointerExceptions.

Thank you, but what about kwdikoi, as you said this will not fix all exceptions. This worked for onomata and eponyma but the error keeps at kwdikoi now. How I can initialize this because it is integer. Sorry if i am asking something obvious but i am new! — kyriakos, Apr 30 '20 at 01:37
`kwdikoi` is an integer array so it will be `kwdikoi = new int[baseArray.size()];` — Harshal Parekh, Apr 30 '20 at 01:38

Exception in thread "main" java.lang.NullPointerException1000

1 Answers1