Java 8 Optional. Why of and ofNullable?

Question

I have a question regarding Java 8\'s Optional, the purpose of which is to tackle NullPointerException exceptions.

The question is, what is the reason for h

Answer 1

Code example: Optional.of() VS Optional.ofNullable()

@Test
public void TestOptional() {

    String message = "Hello World!";
    System.out.println("message -> " + message + "\n");

    Optional<String> genderOptional = Optional.of(message);
    System.out.println("Optional.of(message) -> " + genderOptional);
    System.out.println("Optional.of(message).get() -> " + genderOptional.get());
    try {
        Optional.of(null);
    } catch (java.lang.NullPointerException e) {
        System.out.println("Optional.of(null) -> java.lang.NullPointerException \n");
    }

    System.out.println("Optional.empty() -> " + Optional.empty() + "\n");

    System.out.println("Optional.ofNullable(null) -> " + Optional.ofNullable(null));
    System.out.println("Optional.ofNullable(message) -> " + Optional.ofNullable(message));
    System.out.println("Optional.ofNullable(message).get() -> " + Optional.ofNullable(message).get());

}

Output:

message -> Hello World!

Optional.of(message) -> Optional[Hello World!]
Optional.of(message).get() -> Hello World!
Optional.of(null) -> java.lang.NullPointerException 

Optional.empty() -> Optional.empty

Optional.ofNullable(null) -> Optional.empty
Optional.ofNullable(message) -> Optional[Hello World!]
Optional.ofNullable(message).get() -> Hello World!

Answer 2

Why would people opt for Optional instead of normal if-else method for null checking?

The main point of Optional<T> class is to provide a mean for performing null safe mapping operations.

employeeOptional.map(Employee::getName).map(String::toUpperCase).ifPresent(upperCasedNameConsumer)

The expression above can replace a cascade of if-else statements in a single readable expression.

Optional.of provides an assertion for the given argument to be a null-null value, otherwise, you can opt for Optional.ofNullable if you are not sure about the input.

I strongly recommend you to read the javadoc for Optional<T> class for more optional chaining methods that you can use for your advantage.