RxJava : How to handle error with zip operator ?

You can use onErrorResumeNext to return some Observable or onErrorReturn to return some default value to zip, like:

Observable.zip(
   responseOneObservable
       .onErrorReturn(new Func1<Throwable, ResponseOne>() {
        @Override
        public ResponseOne call(final Throwable throwable) {
            return new ResponseOne();
        }
    }),
   responseTwoObservable
       .onErrorReturn(new Func1<Throwable, ResponseTwo>() {
        @Override
        public ResponseTwo call(final Throwable throwable) {
            return new ResponseTwo();
        }
    }),
   ...

See onError handling for more info.

---

UPDATE: With RxJava 2.0 you must use Function instead of Func1:

import io.reactivex.functions.Function;
...
Observable.zip(
   responseOneObservable
       .onErrorReturn(new Function<Throwable, ResponseOne>() {
        @Override
        public ResponseOne apply(@NonNull final Throwable throwable) {
            return new ResponseOne();
        }
    }),
   responseTwoObservable
       .onErrorReturn(new Function<Throwable, ResponseTwo>() {
        @Override
        public ResponseTwo apply(@NonNull final Throwable throwable) {
            return new ResponseTwo();
        }
    }),
   ...

Or using lambdas:

Observable.zip(
   responseOneObservable
       .onErrorReturn(throwable -> new ResponseOne()),
   responseTwoObservable
       .onErrorReturn(throwable -> new ResponseTwo()),
   ...

Or using Kotlin:

Observable.zip(
   responseOneObservable
       .onErrorReturn { ResponseOne() },
   responseTwoObservable
       .onErrorReturn { ResponseTwo() },
   ...

You can return default response from either of two observables with onErrorResumeNext operator.

Observable<ResponseOne> responseOneObservable = getRetrofitClient().getDataOne()
    .onErrorResumeNext(throwable -> {/*some default value*/})
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread());

Observable<ResponseTwo> responseTwoObservable = getRetrofitClient().getDataTwo()
    .onErrorResumeNext(throwable -> {/*some default value*/})
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread());

Also see Error handling in RxJava - Dan Lew