Check if String is null from a Class

Question

i know that my question is a duplicate of some question here before, i tried every solution that i see from that, but no solution work for me

i have a class named FilingModel and a method name getReason, i always get a null value to my tvReason TextView

public class FilingAdapter extends RecyclerView.Adapter<FilingAdapter.FilingHolder> {
  List<FilingModel> lists;
    @Override
    public void onBindViewHolder(@NonNull FilingHolder holder, int position) {
     FilingModel model = lists.get(position);
     holder.tvReason.setText(model.getReason());
   }

}

public class FilingModel {

    private String reason;

    public FilingModel(String reason) {
        this.reason = reason;
    }

    public String getReason() {
        if ( reason.isEmpty() || TextUtils.isEmpty(reason) || reason.equals(null)) {
           reason = "-";
        }
        return reason;
    }
}

`reason.equals(null)` will throw NullPointerException if `reason` is null. It should be `reason == null` — Eran, Jan 14 '20 at 09:20
You could just initialize `reason` with `"-"`, like `private String reason = "-";`. That way, it won't become `null` until it is explicitly set to... — deHaar, Jan 14 '20 at 09:21
Also `reason==null` needs to be checked before `reason.isEmpty()`. — khelwood, Jan 14 '20 at 09:22
can you show the scenario, how do you use it, so you always get null ? — P.Juni, Jan 14 '20 at 09:23
@P.Juni i'm using it to my RecycleView Adapter, to setText my, TextView tvReason — Marlon, Jan 14 '20 at 09:29
In this case you might want to check if your list is properly initialised. Though I concur with @deHaar, setting the `reason` to `-` by default will not only make sure that you have the default value to fall back to, but also clean up your getter method (it's better to have simple getter and setters without any business logic) — GameDroids, Jan 14 '20 at 09:39

score 0 · Answer 1 · answered Jan 14 '20 at 09:25

0

String checks for null are rather straight forward (once you have done it):

First you want to check if the instance is null (otherwise all further manipulation might fail):

 if(reason == null)

Then you want to check if it is empty as you already did it but maybe you want to trim it first (to remove all whitespaces):

if(reason == null || reason.trim().isEmpty())

as you can see you can chain the conditions with or since Java will stop evaluating the conditions once one of them was found true . So if your string is null, Java will not evaluate if it is empty.

And that's all you need, null and isEmpty (and optionally with a trim())

public String getReason() {
    if(reason==null || reason.trim().isEmpty()){
       reason = "-";
    }
    return reason;
}

answered Jan 14 '20 at 09:25

GameDroids

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i tried it, but it still not working for me – Marlon Jan 14 '20 at 09:28
FYI, the short version (without trim) is simply `if(reason == null || reason.isEmpty())` no need for `TextUtils` or other external tools. Just keep in mind that you first check for null before you check anything else. – GameDroids Jan 14 '20 at 09:30
what exactly is not working? are you getting an Exception or is the result different from what you expect? – GameDroids Jan 14 '20 at 09:31
@GameDriods i don't get any exception – Marlon Jan 14 '20 at 09:44

Bonum Ursus · Answer 2 · 2020-01-14T09:27:05.800

-1

Give type to your variable reason. For example String.

private String reason;

+

if(reason == null)

edited Jan 14 '20 at 09:27

answered Jan 14 '20 at 09:23

Bonum Ursus

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first need to check null otherwise null pointer exception – ThavaSelvan Jan 14 '20 at 09:25
Thank you i have it already, – Marlon Jan 14 '20 at 09:25

Check if String is null from a Class

2 Answers2