fix: use concatEager vs concat courtesy Jake's suggestion

Kaushik Gopal · Kaushik Gopal · commit 035836185f60 · 2016-10-12T22:55:08.000-07:00
🙏 [Jedi Jake](https://twitter.com/JakeWharton/status/786362280535592961).
diff --git a/README.md b/README.md
@@ -103,10 +103,12 @@ The value of this technique becomes more apparent when you have more number of i
 
 ### Retrieve data first from a cache, then a network call - using [`.concat`](http://reactivex.io/documentation/operators/concat.html)
 
-Using concat, you can retrieve information from an observable first (presumably this one is fast like retrieveing from a disk cache) and show preliminary data to a user. Subsequently, when the longer running 2nd observable is complete (say a network call), you can update the results on the interface using the latest information.
+Using concat, you can retrieve information from an observable first (presumably this one is fast like retrieving from a disk cache) and show preliminary data to a user. Subsequently, when the longer running 2nd observable is complete (say a network call), you can update the results on the interface using the latest information.
 
 For the purposes of illustration i use an in-memory `List` (not an actual disk cache), then shoot out a real network call to the github api so it gives you a feel of how this can really be applied in production apps.
 
+Note the use of `concatEager` here over the traditional `concat` operator. Both show the results from the `Observables` in a sequential manner (so disk first and then network). The `concat` operator however would not even begin the subscription on subsequent Observables unless the first one is complete whereas `concatEager` kicks off all Observables at the time of Subscription in parallel, but still preserves order.
+
 **Update:**
 
 After a [conversation I had with @artem_zin](https://twitter.com/kaushikgopal/status/591271805211451392), we arrived at an alternative solution to the same problem. One that used the [`.merge`](http://reactivex.io/documentation/operators/merge.html) operator instead.
diff --git a/app/src/main/java/com/morihacky/android/rxjava/fragments/PseudoCacheConcatFragment.java b/app/src/main/java/com/morihacky/android/rxjava/fragments/PseudoCacheConcatFragment.java
@@ -57,7 +57,7 @@ public void onDemoPseudoCacheClicked() {
         _resultList.setAdapter(_adapter);
         _initializeCache();
 
-        Observable.concat(_getCachedData(), _getFreshData())
+        Observable.concatEager(_getCachedData(), _getFreshData())
               .subscribeOn(Schedulers.io())
               .observeOn(AndroidSchedulers.mainThread())
               .subscribe(new Subscriber<Contributor>() {
