RxJava - Combining Operators

Following are the operators which are used to create a single Observable from multiple Observables.

Sr.No. Operator & Description
1 And/Then/When

Combine item sets using Pattern and Plan intermediaries.

2 CombineLatest

Combine the latest item emitted by each Observable via a specified function and emit resulted item.

3 Join

Combine items emitted by two Observables if emitted during time-frame of second Observable emitted item.

4 Merge

Combines the items emitted of Observables.

5 StartWith

Emit a specified sequence of items before starting to emit the items from the source Observable

6 Switch

Emits the most recent items emitted by Observables.

7 Zip

Combines items of Observables based on function and emits the resulted items.

Combining Operator Example

Create the following Java program using any editor of your choice in, say, C:\> RxJava.


import io.reactivex.Observable;
//Using combineLatest operator to combine Observables
public class ObservableTester {
   public static void main(String[] args) {    
      Integer[] numbers = { 1, 2, 3, 4, 5, 6};
      String[] letters = {"a", "b", "c", "d", "e", "f", "g"};
      final StringBuilder result = new StringBuilder();
      Observable<String> observable1 = Observable.fromArray(letters);
      Observable<Integer> observable2 = Observable.fromArray(numbers);
      Observable.combineLatest(observable1, observable2, (a,b) -> a + b)
         .subscribe( letter -> result.append(letter));

Verify the Result

Compile the class using javac compiler as follows −

C:\RxJava>javac ObservableTester.java

Now run the ObservableTester as follows −

C:\RxJava>java ObservableTester

It should produce the following output −