Sunday, March 25, 2018

JShell and Optional 

jshell> List<String> people = List.of("Bill", "Sue", "Jenny", "Sarah", "Tim", "Brian");
people ==> [Bill, Sue, Jenny, Sarah, Tim, Brian]

jshell> people.stream().filter(p -> p.substring(0,1).equals("B"))
    .forEach(System.out::println)
Bill
Brian

jshell> List<String> results = people.stream().
   ...> filter(p -> p.substring(0,1).equals("B")).
   ...> collect(Collectors.toList())
results ==> [Bill, Brian]

jshell> Optional<String> s = people.stream().
   ...> filter(p -> p.startsWith("T")).
   ...> findFirst()
s ==> Optional[Tim]

jshell> Optional<String> s = people.stream().
   ...> filter(p -> p.startsWith("W")).
   ...> findFirst()
s ==> Optional.empty

jshell> System.out.println(s.orElse("not found"))
not found

jshell>

at