Convert this null check to java 8 Optional

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I am unable to understand how to remove the below null check by using Java 8 Optional

for (A objA : listOfObjectsA) {
    if (objA.getStringField() == null) continue;
        // some code to do if not null
}

if "some code to do if not null" only operates on objA.getStringField() then you can do:

listOfObjectsA.stream()
              .map(A::getStringField)
              .filter(Objects::nonNull)
              .forEach(e -> ...);

However, if you still want to have access to the A elements then as the other answers have shown you have no choice but to perform an explicit objA.getStringField() != null:

listOfObjectsA.stream()
              .filter(a -> a.getStringField() != null)
              .forEach(a -> ...);

Guide To Java 8 Optional, Quick and practical guide to Optional in Java 8. A value is present only if we have created Optional with a non-null value. We'll look at We can use a similar syntax to transform the Optional value with the map() method: ? Optional is a container object that may or may not contain a non-null value. To interact with the value, Optional offers a set of useful methods that abstract away the null checks. This leaves us with more concise and declarative code that is focused on the details we care about.

You don't have to use Optionals for that. You can filter the null elements using a Stream:

listOfObjectsA.stream()
              .filter(objA -> objA.getStringField() != null)
              .forEach (... do something  ...);

To use Optional you can write Optional.ofNullable(objA.getStringField()).isPresent(), but that seems pointless.

Java 8 Optional: Handling Nulls Properly, Java 8 introduced the Optional class to make handling of nulls less error-prone. This null check can be replaced with the Optional class method Roughly all we understanding within JavaScript will turn out to be an object. There have been a couple of articles on null, NPE's and how to avoid them. They make some point, but could stress the easy, safe, beautiful aspects of Java 8's Optional.

You could replace your code with Java8 style with streams and Optional. But I presonally think that in this concrete case, this is not better that POJO (which is much more simplier and readable):

Optional.ofNullable(listOfObjectsA).orElse(Collections.emptyList()).stream()
        .filter(Objects::nonNull)
        .filter(objA -> Objects.nonNull(objA.getStringField()))
        .forEach(objA -> {
            // some code to do if not null
        });

If you're sure, that given list cannot be null and each element objA cannot be null as well, then you can definitely avoid some useless checks in this case:

listOfObjectsA.stream()
        .filter(objA -> Objects.nonNull(objA.getStringField()))
        .forEach(objA -> {
            // some code to do if not null
        });

Tired of Null Pointer Exceptions? Consider Using Java SE 8's , Java SE 8 introduces a new class called j ava.util.Optional<T> that is inspired from the ideas of Haskell and Scala. It is a class that encapsulates an optional value,  I am refactoring the code to Java 8 and I want to replace null checks with Optional. public Employee findEmployeeById(String id) { List<Employee> empList = .. //some db query return

Ideally without optional, you can do

listOfObjectsA.stream().filter(objA -> objA.getStringField() != null)
                       .forEach(objA -> { /* some code to do if not null*/ });

Java Optional Tutorial with Examples, Null checks in programs are often overlooked by developers causing serious bugs in code. Java 8 introduced a new type called Optional<T> to  Java 8 has introduced a new class Optional in java.util package. It is used to represent a value is present or absent. The main advantage of this new construct is that No more too many null checks and NullPointerException. It avoids any runtime NullPointerExceptions and supports us in developing clean and neat Java APIs or Applications.

Why use Optional in Java 8+ instead of traditional null pointer checks?, Style 2 isn't going Java 8 enough to see the full benefit. You don't want the if use at all. See Oracle's examples. Taking their advice, we get:. Given a String I need to get an Optional, whereby if the String is null or empty the result would be Optional.empty. I can do it this way: String ppo = ""; Optional&lt;String&gt; ostr = Optional.

Java 8 Optional In Depth, util package. It is used to represent a value is present or absent. The main advantage of this new construct is that No more too many null checks  Note that slight semantic difference: the question’s code uses ofNullable which implies that an empty Optional is returned if the list is non-empty but contains a null at the first place. In contrast Stream.findFirst() will throw an exception if an element is present, but null .

Working on Null Elegantly with Java Optional - FAUN, Today I learn how to work on null object elegantly with java optional class, and I want to share with you. Optional By using Optional<Reservation> as a return value of findById function, we You still can transform any object into Optional by using Optional.of and Optional. Optional (Java Platform SE 8 )  Optional.ofNullable() is for something that may be null, such as a method that may return null, like the example above. Optional.empty() is for a creating an Optional that contains nothing. We then call isPresent() to see if the Optional contains a value. This simply replaces the null check with a call to a boolean method.

Comments
  • Thank you, but even in the above code there is the null check present? So seems like null check is unavoidable in this scenario.
  • I posted my comment before you made the edit. Thank you
  • @Saad If you wrap the value that might be null with an Optional, you can perform actions on it without directly checking for null, but whether or not it makes sense depends on the specific use case.
  • You can use Optional.stream() in combination with flatMap - still pointless but less pointless than filter with isPresent.
  • isn't that too complicated than simple filter and forEach?
  • @nullpointer Yes, I think so. In this situation, I like POJO with if..else more