RxJava - Filtering Operators

Filter operator filters an Observable making sure that emitted items match specified condition.

Following are the operators which are used to selectively emit item(s) from an Observable.

Sr.No. Operator & Description
1

Debounce

Emits items only when timeout occurs without emiting another item.
2

Distinct

Emits only unique items.
3

ElementAt

emit only item at n index emitted by an Observable.
4

Filter

Emits only those items which pass the given predicate function.
5

First

Emits the first item or first item which passed the given criteria.
6

IgnoreElements

Do not emits any items from Observable but marks completion.
7

Last

Emits the last element from Observable.
8

Sample

Emits the most recent item with given time interval.
9

Skip

Skips the first n items from an Observable.
10

SkipLast

Skips the last n items from an Observable.
11

Take

takes the first n items from an Observable.
12

TakeLast

takes the last n items from an Observable.

 

Examples:

public class RxFiltering {
    public static void main(String args[])
    {
        Observable sourceObservable = Observable.range(1, 10);
        

        Observable filteredObservable = sourceObservable
          .filter(i -> i % 2 != 0);

        filteredObservable.subscribe(s->System.out.println(s
      ));
    }
}

Output

1

3

5

7

9

 

Example 2:

 Observable sourceObservable = Observable.range(1, 10);
          Observable takeObservable = sourceObservable
          .take(2);

            takeObservable.subscribe(s->System.out.println(s
          ));

Output

1

2

 

Example 3:

 Observable sourceObservable = Observable.range(1, 10);
             Observable takeWhileObservable = sourceObservable
          .takeWhile(i -> i < 5 );

            takeWhileObservable.subscribe(s->System.out.println(s
          ));

Output

1

2

3

4

 

Example 4:

Observable sourceObservable = Observable.range(1, 10);
        Maybe filteredObservable = sourceObservable.elementAt(4);
 
                    filteredObservable.subscribe(s->System.out.println(s));

 

Output

5

*

RXJava Tutorials
RxJava Tutorial RxJava - Environment Setup RxJava’s Characteristics RxJava - How Observable works RxJava - Single Observable RxJava - MayBe Observable RxJava - Completable Observable RxJava - Using CompositeDisposable RxJava - Creating Operators RxJava - Transforming Operators RxJava - Filtering Operators RxJava - Combining Operators RxJava - Utility Operators RxJava - Conditional Operators RxJava - Mathematical Operators RxJava - Subjects RxJava - PublishSubject RxJava - BehaviorSubject RxJava - AsyncSubject RxJava - ReplaySubject RxJava - Schedulers RxJava - Trampoline Scheduler RxJava - NewThread Scheduler RxJava - Computation Scheduler RxJava - IO Scheduler RxJava - From Scheduler RxJava - Buffering