set value in optional java code example

Example 1: instantiate optinal java 8

Person p = new Person();
Optional<Person> op = Optional.of(p);

Example 2: java optional to collection

public static <T> List<T> toList(Optional<T> opt) {
    return opt
            .map(Collections::singletonList)
            .orElseGet(Collections::emptyList);
}