java 8 stream - handle if nothing is found

Question

The following stream pipeline does not work if nothing is found, in which case .findFirst() throws a NPE.

How can I prevent this?

scheduleDurationContainers.stream()
        .filter(s -> s.getContainerType() == ScheduleIntervalContainerTypeEnum.BONUS).findFirst().get()

Answer 1

You can replace get() with orElse(someDefault), which would return some default value if the Optional returned by findFirst is empty. Or you can use orElseThrow(execptionSupplier) if you want to throw some specific exception when findFirst doesn't find anything.

Answer 2

If you want to return default value if there is nothing to return using lambda expression then you should use findAny() and orElse() in following sequence

Person result1 = persons.stream()                          // Convert to stream
                 .filter(x -> "answer".equals(x.getName()))  // we want to filter "answer" only
                 .findAny()                                // If 'findAny' then return found
                 .orElse(null);                            // If not found, return null