RxJava - Filtering Operators

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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.

Filtering Operator Example

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

ObservableTester.java

import io.reactivex.Observable;
//Using take operator to filter an Observable
public class ObservableTester  {
   public static void main(String[] args) {    
      String[] letters = {"a", "b", "c", "d", "e", "f", "g"};
      final StringBuilder result = new StringBuilder();
      Observable<String> observable = Observable.fromArray(letters);
      observable
         .take(2)
         .subscribe( letter -> result.append(letter));
      System.out.println(result);
   }
}

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 −

ab
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