When to use of() and ofNullable() methods of Optional in Java?

If you want to create an Optional type object in Java, you can make use of either of () and ofNullable() methods.

Let's try and understand when to use which.

Optional.of(T t)

One should make use of the static of(T t) method when quite sure that the value of the object is non-null.

It is important to note that if the provided object is null, you will get a NullPointerException when trying to perform operations on a null value.

Example:

import java.util.Optional;

public class ExampleOptionalOf {

    public static void main(String[] args) {

        String strObject1 = "Coe2care";
        Optional<String> optionalValue1 = Optional.of(strObject1);
        optionalValue1.ifPresent(System.out::println);

        String strObject2 = null;
        Optional<String> optionalValue2 = Optional.of(strObject2);
        optionalValue2.ifPresent(System.out::println);

    }
}

Output:

Coe2care

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:233)
	at java.base/java.util.Optional.of(Optional.java:113)
	at ExampleOptionalOf.main(ExampleOptionalOf.java:12)

Optional.ofNullable(T t)

The ofNullable(T t) static method is more lenient and can handle null values.

Example:

import java.util.Optional;

public class ExampleOptionalOfNullable {

    public static void main(String[] args) {

        String strObject1 = "Coe2care";
        Optional<String> optionalValue1 = Optional.ofNullable(strObject1);
        optionalValue1.ifPresent(System.out::println);

        String strObject2 = null;
        Optional<String> optionalValue2 = Optional.ofNullable(strObject2);
        optionalValue2.ifPresentOrElse(
                System.out::println,
                () -> System.out.println("Value is empty!"));


    }
}

Conculstion

• Use Optional.of(T t) when certain the value is non-null, note - risking a NullPointerException if null.
• Use Optional.ofNullable(T t) for flexibility, handling both non-null and null values without causing exceptions.