[FIXED] Java null check on multiple properties with Optionals

Issue

What's the most efficient way on java 11 to null check multiple fields from the same object? I was going with optionals but I don't understand how to use them with more fields of the same object

    Map<String, NestedQuery> nested = new HashMap<>();
    if (getSentDate() != null) {
      if (getSentDate().getFrom() != null && getSentDate().getTo() != null) {
        nested.put(...); 
      }
    }
    return nested;

In my case getSentdate() returns an object that has getFrom() and getTo() that are values that may or may not be null

I tried with this but the use of .ifPresent inside an if clause is a big no no

    Map<String, NestedQuery> nested = new HashMap<>();
    Optional.ofNullable(getSentDate())
        .ifPresent(sentDate -> {
          Optional<String> from = Optional.ofNullable(sentDate.getFrom());
          Optional<String> to = Optional.ofNullable(sentDate.getTo());
          if(from.isPresent() && to.isPresent()){
            nested.put(...);
          }
        });
    return nested;

Solution

As it has been said in the comments above your original code is actually quite efficient (we probably need some criteria for effectiveness):

if (getSentDate() != null) {
      if (getSentDate().getFrom() != null && getSentDate().getTo() != null) {

However if you really want to use an Optional to eliminate some of the null checks it is enough to use just one:

Optional.ofNullable(getSentDate())
        .filter(sentDate -> Objects.nonNull(sentDate.getFrom()))
        .filter(sentDate -> Objects.nonNull(sentDate.getTo())) 
        .ifPresent(date -> nested.put(...)); 

in this case .ifPresent(date -> nested.put(...)) is executed only when all 3 conditions are met: getSentDate() is not null, sentDate.getFrom() is not null and sentDate.getTo() is not null as well. However we still have a null check and we are "abusing" Objects#nonNull method since:

API Note: This method exists to be used as a Predicate, filter(Objects::nonNull)

An equivalent for this is

Optional.ofNullable(getSentDate())
        .filter(sentDate -> sentDate.getFrom() != null)
        .filter(sentDate -> sentDate.getTo() != null) 
        .ifPresent(date -> nested.put(...)); 

Please note as well that this actually "violates" Optional usage

API Note: Optional is primarily intended for use as a method return type where there is a clear need to represent "no result," and where using null is likely to cause errors.

Answered By - Anton Balaniuc
Answer Checked By - Candace Johnson (JavaFixing Volunteer)