unboxing of snapshot.getvalue(double.class) may produce nullpointer exception

Question

Snapshot.getValue is producing null pointer exception,how should i solve this error?

DatabaseReference offsetRef = FirebaseDatabase.getInstance().getReference(".info/serverTimeOffset");
        offsetRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                double offset = snapshot.getValue(Double.class);

It sounds like `.info/serverTimeOffset` may not exist, which means that the `Double` you get out of it is `null`, which can't be unboxed. The solution would be to make the type `Double offset = ...` or to unbox after checking for `null`. See https://stackoverflow.com/questions/2382058/unboxing-null-object-to-primitive-type-results-in-nullpointerexception-fine — Frank van Puffelen, Dec 02 '20 at 19:54

score 0 · Answer 1 · answered Dec 02 '20 at 19:54

snapshot.getValue(Double.class) returns a Double object, not a double primitive. You should check this object for null before unboxing it. It can be null when no data exists in the snapshot.

Double offset = snapshot.getValue(Double.class);
if (offset != null) {
    double o = offset;
}
else {
    // figure out what you want to do when the data is not there
}

score 0 · Answer 2 · answered Dec 02 '20 at 19:56

There are a few options. You can write it in a try...catch

double offset;

try {
    offset = snapshot.getValue(Double.class);
}catch(Exception e){
    offset = 0; //Default value
}

Another option is to use a ternary operator

double offset = snapshot.getValue(Double.class) != null ? snapshot.getValue(Double.class) : 0;

unboxing of snapshot.getvalue(double.class) may produce nullpointer exception

2 Answers2