takeWhile() and skipWhile()

Another variant of the take() operator is the takeWhile() operator, which takes emissions while a condition derived from each emission is true. The following example will keep taking emissions while emissions are less than 5. The moment it encounters one that is not, it will call the onComplete() function and dispose of this:

import io.reactivex.Observable;

public class Launcher {
      public static void main(String[] args) {

        Observable.range(1,100)
          .takeWhile(i -> i < 5)
          .subscribe(i -> System.out.println("RECEIVED: " + i));
      }
}

The output of the preceding code snippet is as follows:

RECEIVED: 1
RECEIVED: 2
RECEIVED: 3
RECEIVED: 4

Just like the takeWhile() function, there is a skipWhile() function. It will keep skipping emissions while they qualify with a condition. The moment that condition no longer qualifies, the emissions will start going through. In the following code, we skip emissions as long as they are less than or equal to 95. The moment an emission is encountered that does not meet this condition, it will allow all subsequent emissions going forward:

import io.reactivex.Observable;

public class Launcher {
      public static void main(String[] args) {

        Observable.range(1,100)
          .skipWhile(i -> i <= 95)
          .subscribe(i -> System.out.println("RECEIVED: " + i));
      }
}

The output of the preceding code snippet is as follows:

RECEIVED: 96
RECEIVED: 97
RECEIVED: 98
RECEIVED: 99
RECEIVED: 100