Optional class in Java

Last Updated : 17 Mar 2025

Java introduced a new class Optional in JDK 8 version. It is a public final class and used to deal with NullPointerException in Java application. We must import java.util package to use this class. It provides methods that are used to check the presence of value for particular variable.

Java Optional Class Methods

Methods	Description
public static <T> Optional<T> empty()	It returns an empty Optional object. No value is present for this Optional.
public static <T> Optional<T> of(T value)	It returns an Optional with the specified present non-null value.
public static <T> Optional<T> ofNullable(T value)	It returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional.
public T get()	If a value is present in this Optional, returns the value, otherwise throws NoSuchElementException.
public boolean isPresent()	It returns true if there is a value present, otherwise false.
public void ifPresent(Consumer<? super T> consumer)	If a value is present, invoke the specified consumer with the value, otherwise do nothing.
public Optional<T> filter(Predicate<? super T> predicate)	If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.
public <U> Optional<U> map(Function<? super T,? extends U> mapper)	If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise return an empty Optional.
public <U> Optional<U> flatMap(Function<? super T,Optional<U> mapper)	If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional.
public T orElse(T other)	It returns the value if present, otherwise returns other.
public T orElseGet(Supplier<? extends T> other)	It returns the value if present, otherwise invoke other and return the result of that invocation.
public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X extends Throwable	It returns the contained value, if present, otherwise throw an exception to be created by the provided supplier.
public boolean equals(Object obj)	Indicates whether some other object is "equal to" this Optional or not. The other object is considered equal if: It is also an Optional and; Both instances have no value present or; the present values are "equal to" each other via equals().
public int hashCode()	It returns the hash code value of the present value, if any, or returns 0 (zero) if no value is present.
public String toString()	It returns a non-empty string representation of this Optional suitable for debugging. The exact presentation format is unspecified and may vary between implementations and versions.

Example: Java Program Without Using Optional

In the following example, we are not using Optional class. The program terminates abnormally and throws a NullPointerException.

File Name: OptionalExample.java

Output:

Exception in thread "main" java.lang.NullPointerException
	at lambdaExample.OptionalExample.main(OptionalExample.java:6)

To avoid the abnormal termination, we use Optional class. In the following example, we are using Optional. So, our program can execute without crashing.

Java Optional Example: If Value is not Present

File Name: OptionalExample.java

Output:

string value is not present

Java Optional Example: If Value is Present

File Name: OptionalExample.java

Output:

java optional class example

Another Java Optional Example

Output:

JAVA OPTIONAL CLASS EXAMPLE
JAVA OPTIONAL CLASS EXAMPLE
java optional class example

Java Optional Methods Example

File Name: OptionalExample.java

Output:

Optional.empty
Filtered value: Optional.empty
Filtered value: Optional[JAVA OPTIONAL CLASS EXAMPLE]
Getting value: JAVA OPTIONAL CLASS EXAMPLE
Getting hashCode: -619947648
Is value present: true
Nullable Optional: Optional[JAVA OPTIONAL CLASS EXAMPLE]
orElse: JAVA OPTIONAL CLASS EXAMPLE
orElse: Value is not present
JAVA OPTIONAL CLASS EXAMPLE

Using Alternate Values if Value is not Present: orElse() and orElseGet()

The methods orElse() and orElseGet() in Java's Optional class are used to retrieve a value from an Optional object when the contained value is not present. Both serve similar purposes but differ slightly in how they operate. Let's see the usages of these two methods through a Java program.

File Name: OptionalOrElseExample.java

Output:

Name with orElse: Default User
Computing default username...
Name with orElseGet: Computed Default User

Optional Value Transformation With map() and flatMap()

Using map() Method

The map() method applies a function to the value inside the Optional if it is present. It then wraps the result in a new Optional. This is useful for transforming the value while still keeping it within an Optional container.

File Name: OptionalFilterExample.java

Output:

JOHN DOE

Using flatMap() Method

The flatMap() method applies a function to the value inside the Optional, and the function must return an Optional. This is useful when you want to avoid nested Optional (i.e., Optional<Optional<T>>) structures and instead get a flat structure of Optional<T>.

File Name: OptionalFlatMapExample.java

Output:

Name length: 8

Conditionally Returning Values With the filter() Method

The filter() method in Java's Optional class provides a way to conditionally return values based on a predicate. If a value is present in the Optional and it matches the predicate, the Optional is returned as-is; if the value does not match the predicate, an empty Optional is returned. This method is useful for applying conditional logic in a chain of Optional operations without needing explicit null-checks or conditional statements.

Basic Usage of filter() Method

Here is an example demonstrating how to use filter() to check a condition on the contained value. We will create a scenario where we check if a user's name is "admin" and perform an action based on that check.

File Name: OptionalFilterExample.java

Output:

User is an admin

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