Streams were initiated in java to help developers perform a collection of operations from a sequence of objects. Few more methods are added to make streams better with java 9.
Syntax
default Stream<T> takeWhile(Predicate<? super T> predicate)
takeWhile method takes all the values up to predicate returns false. It returns, in case or ordered stream, a stream consisting of the biggest prefix of elements that get hold of from this stream matching the given predicate.
Example
import java.util.stream.Stream; public class Tester { public static void main(String[] args) { Stream.of("a","b","c","","e","f").takeWhile(s->!s.isEmpty()) .forEach(System.out::print); } }
Output
takeWhile way takes all a,b and c values, then once the string is empty it pauses executing.
abc
Syntax
default Stream<T> dropWhile(Predicate<? super T> predicate)
drop while a method to lob away all the values at the start-up to the predicate returns true. It gives back, in the case of an ordered stream, a stream consisting of the remaining elements of this stream after dropping the longest prefix of components matching the given predicate.
Example
import java.util.stream.Stream; public class Tester { public static void main(String[] args) { Stream.of("a","b","c","","e","f").dropWhile(s-> !s.isEmpty()) .forEach(System.out::print); System.out.println(); Stream.of("a","b","c","","e","","f").dropWhile(s-> !s.isEmpty()) .forEach(System.out::print); } }
Output
dropwhile method drops a,b,and c values, then once the string becomes empty it will take all the values.
ef ef
Syntax
static <T> Stream<T> iterate(T seed, Predicate<? super T> hasNext, UnaryOperator<T> next)
iterate now has hasnextPredicate as parameter which pauses the loop once hasNextPredicate returns false.
Example
import java.util.stream.IntStream; public class Tester { public static void main(String[] args) { IntStream.iterate(3, x -> x < 10, x -> x+ 3).forEach(System.out::println); } }
Output
3 6 9
Syntax
static <T> Stream<T> ofNullable(T t)
ofNullable method is launched to prevent NullPointersExceptions and to avoid null checks for streams. This method returns a sequential stream holding a single element, if non-null, otherwise gives back an empty stream.
Example
import java.util.stream.Stream; public class Tester { public static void main(String[] args) { long count = Stream.ofNullable(100).count(); System.out.println(count); count = Stream.ofNullable(null).count(); System.out.println(count); } }
Output
1 0