JAVA OPTIONAL CLASS

application

public static void main(String[] args) {

  Optional<String> hello = Optional.ofNullable(null);

   // 1. Optional Use:
  // check value is present in hello
   System.out.println(hello.isPresent());
  // check if hello(v) is empty
   System.out.println(hello.isEmpty());


  // 2. orElse:  if hello doesn't contain any value
  // then $hello = world
   String orElse = hello
          .map(String::toUpperCase)
           .orElseGet(() -> {
               //.. extra computation to retrieve the value
               return "world";
           });
   System.out.println(orElse);

  // 3. check if hello exists
  // otherwise world will display.
  hello.ifPresentOrElse(System.out::println, () -> System.out.println("World"));

}