Optional vs. null. What is the purpose of Optional in Java 8? [duplicate]

by

In practice, why is this useful?

For example let’s say you have this stream of integers and you’re doing a filtering:

int x = IntStream.of(1, -3, 5)
                 .filter(x -> x % 2 == 0)
                 .findFirst(); //hypothetical assuming that there's no Optional in the API

You don’t know in advance that the filter operation will remove all the values in the Stream.

Assume that there would be no Optional in the API. In this case, what should findFirst return?

The only possible way would be to throw an exception such as NoSuchElementException, which is IMO rather annoying, as I don’t think it should stop the execution of your program (or you’d have to catch the exception, not very convenient either) and the filtering criteria could be more complex than that.

With the use of Optional, it’s up to the caller to check whether the Optional is empty or not (i.e if your computation resulted in a value or not).

With reference type, you could also return null (but null could be a possible value in the case you filter only null values; so we’re back to the exception case).

Concerning non-stream usages, in addition to prevent NPE, I think it also helps to design a more explicit API saying that the value may be present or not. For example consider this class:

class Car {
   RadioCar radioCar; //may be null or not 
   public Optional<RadioCar> getRadioCar() {
        return Optional.ofNullable(radioCar);
   }
}

Here you are clearly saying to the caller that the radio in the car is optional, it might be or not there.

More Related Contents:

  1. Word count in descending order using java lambdas
  2. When to use: Java 8+ interface default method, vs. abstract method
  3. Why does a Java method reference with return type match the Consumer interface?
  4. Cannot parse String in ISO 8601 format, lacking colon in offset, to Java 8 Date
  5. How can I count occurrences with groupBy?
  6. Lambdas: local variables need final, instance variables don’t
  7. What is difference between Collection.stream().forEach() and Collection.forEach()?
  8. How to get the MethodInfo of a Java 8 method reference?
  9. Convert java.time.LocalDate into java.util.Date type
  10. _ (underscore) is a reserved keyword
  11. Split list into multiple lists with fixed number of elements in java 8
  12. Chaining Optionals in Java 8
  13. Filter Java Stream to 1 and only 1 element
  14. Java 8 default methods as traits : safe?
  15. Why do I need a functional Interface to work with lambdas?
  16. Maximum size of a method in Java 7 and 8
  17. Find maximum, minimum, sum and average of a list in Java 8
  18. Does Java SE 8 have Pairs or Tuples?
  19. Reflections – Java 8 – invalid constant type
  20. DateTimeFormatter month pattern letter “L” fails
  21. Java streams lazy vs fusion vs short-circuiting
  22. Mock Instant.now() without using Clock into Constructor or without Clock Object
  23. How to sum values in a Map with a stream?
  24. Why can we use ‘this’ as an instance method parameter?
  25. When and why would you use Java’s Supplier and Consumer interfaces?
  26. Implied anonymous types inside lambdas
  27. Default garbage collector for Java 8
  28. Purpose of third argument to ‘reduce’ function in Java 8 functional programming
  29. Does collect operation on Stream close the stream and underlying resources?
  30. How to get multiple values from an object using a single stream operation?

Leave a Comment