3.4 Added mergeWith

Author: Froussios

Part 3 - Taming the sequence/4. Combining sequences.md

@@ -323,6 +323,15 @@ First
 
 The difference between `concat` and `merge` is that `merge` does not wait for the current observable to terminate before moving to the next. `merge` subscribes to every observable available to it and emits items as they come. It that way, `merge` is similar to the flattening part of `flatMap`.
 
+Like other static operators, `merge` has an alternative that allows you to merge sequences one by one in a chain. The operator is called `mergeWith` and the behaviour is the same. The following example has the same result as the one above.
+
+```java
+Observable.interval(250, TimeUnit.MILLISECONDS).map(i -> "First")
+	.mergeWith(Observable.interval(150, TimeUnit.MILLISECONDS).map(i -> "Second"))
+	.take(10)
+	.subscribe(System.out::println);
+```
+
 ### mergeDelayError
 
 With `merge`, as soon as any of the source sequences fails, the merged sequence fails as well. An alternative to that behaviour is `mergeDelayError`, which will postpone the emission of an error and continue to merge values from sequences that haven't failed.