Cannot resolve method 'sumDouble(io.reactivex.Observable<java.lang.Double>)'

Question

In Activity :

Double price = o.getDouble ( "totalprice" );

Observable<Double> floatObservable = Observable.just(price);

MathObservable
       .sumDouble(floatObservable)
       .subscribe(new Observer<Integer>() {
       @Override
       public void onSubscribe(Disposable d) {

       }

       @Override
       public void onNext(Integer integer) {
             System.out.println("Sum: " + integer);
       }

       @Override
       public void onError(Throwable e) {

       }

       @Override
       public void onComplete() {

       }
});

Gradle :

implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
implementation 'io.reactivex:rxjava-math:1.0.0'    

Error occur at line :

.sumDouble(floatObservable)

Error :

Cannot resolve method 'sumDouble(io.reactivex.Observable)'

Answer 1

In your app.gradle add dependencies

  implementation "com.github.akarnokd:rxjava2-extensions:0.20.8"

then

 Observable<Double> floatObservable = Observable.just(1.2,1.3);

    MathObservable
            .sumDouble(floatObservable)
            .subscribe(new Observer<Double>() {
                @Override
                public void onSubscribe(Disposable d) {

                }

                @Override
                public void onNext(Double aDouble) {
                    System.out.println("Sum: " + aDouble);
                   //if you want int convert here
                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {

                }
            });

Its working fine ..answer is 2.5