Java Optional: example with .map() and .orElse()

memberFinder.java

public String memberNameById(List<Member> members, int memberId) {
    return members.stream()
        .filter(member -> member.getId() == memberId)
        .findFirst()               // returns an Optional
        .map(Member::getName)      // transforms the value if present in the Optional
        .orElse("UNKNOWN");        // if the Optional is absent, it returns a default value     
}