RxJava2 - Concat multiple observables, prevent execution if first element found - reactive-programming

Question

Im working on implementing simple data provider with 2 level cache using RxJava2
public static void main(String args[]) {
Observable.concat(getFromMemory(), getFromFileCache(), getFromNetwork())
.firstElement()
.subscribe((integer) ->
{
System.out.println("Completed with val: " + integer);
});
}
static Observable<Integer> getFromMemory() {
return Observable.create(e -> {
System.out.println("Source: Memory");
e.onNext(1);
e.onComplete();
});
}
static Observable<Integer> getFromFileCache() {
try {
Thread.sleep(1000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
return Observable.create(e -> {
System.out.println("Source: FileCache");
e.onNext(2);
e.onComplete();
});
}
static Observable<Integer> getFromNetwork() {
try {
Thread.sleep(2000);
}
catch (InterruptedException e) {
e.printStackTrace();
}
return Observable.create(e -> {
System.out.println("Source: Network");
e.onNext(3);
e.onComplete();
});
}
Goal is to look for object in memory cache,
if not found - read from file, if not found - call network to get resource. Cache update is not important in this sample.
When executing this code, I see console log:
Source: Memory
Source: FileCache
Source: Network
Completed with val: 1
Which mean file cache and network call will be executed, despite memory cache returns value.
Im using rxJava 2, which operator can I use, to combine sources, but stop executing on first valueFound? I experimented with first(default) and take, no luck so far

Answer 1

Actually, its a bug in rxJava2 - upgrading to 2.1.0 helped:
Github issue: https://github.com/ReactiveX/RxJava/issues/5100