Java / Java8 streams
What is Optional class in java?
Inspired from Haskell and Scala, Java SE 8 introduces a new class in util package, java.util.Optional, whose instance hold an object so that it either contains a value or not (empty). It eliminates NullPointerException and the null check constructs.
Example of an empty optional:
Optional<String> str= Optional.empty();
Optional non-empty object:
String str = "javapedia.net"; Optional<String> oStr = Optional.of(str);
public static void main(String[] args) { Optional<String> emptyO = Optional.empty(); System.out.println(emptyO); System.out.println(emptyO.isPresent()); System.out.println(emptyO.orElseGet(()->"AssignThisIfEmpty")); Optional<String> strO = Optional.of("javapedia.net"); System.out.println(strO); System.out.println(strO.isPresent()); System.out.println(strO.get()); }
Output:
Optional.empty false AssignThisIfEmpty Optional[javapedia.net] true javapedia.net
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