Optional with Examples in Java 8

Java 8 has introduced a new class in utils package Optional. This class main purpose is for handling NullPointerExceptions.

So what exactly is Optional?

As per the oracle docs – Optional is a container object which may contain a value or may not contain a value.

In simple terms it means it can have values or it can be empty.

There are many in-build methods that optional has which helps us to avoid NullPointerException.


        String value1 = null;

        Optional<String> value2 = Optional.empty();

        if(value1!=null && value1.isEmpty()) { //Null check required
                System.out.println(value1) ;

        Optional.ofNullable(value2).ifPresent(value -> System.out.println(value)); //Null check is done by optional

Method Explanation
empty()Returns an empty optional instance
filter(Predicate<? super T> predicate)If the value matches it returns optional value or returns optional empty
flatMap(Function<? super T, Optional<U>> mapper)Mapping function if value exists or optional empty
get()Gets the optional value if present or throws NoSuchElementException
ifPresent(Consumer<? super T> consumer)If optional value is present, proceed with consumer invocation or will not perform any operation
isPresent()Returns a boolean value, if value present returns true or false.
map(Function<? super T, ? extends U> mapper)Applies mapping function if the value is present
of(T value)Returns the optional value
ofNullable(T value)Returns a value if present or empty optional
orElse(T other)If value not present it returns the orElse value of other
orElseGet(Supplier<? extends T> other)Returns value if present or invokes other and returns the value
orElseThrow(Supplier<? extends X> exceptionSupplier)Returns value if present or throws the exception
Optional Methods

There also common methods in optional like toString() and hashcode().

Declaring an Optional

Declaring an empty Optional,

Optional<String> value = Optional.empty();

In the above we have declared an Empty Optional, so what does empty optional mean?

Empty Optional?

Optional.empty() is just an object of optional, means

Optional<?> EMPTY = new Optional<>();

Declaring a value for optional:

We cannot declare the string value directly for an Optional<String>, if we try the below

Optional<String> value2 = "value2"; //Compile time error - Wrap it using Optional

So how can we declare a value for an Optional variable?

There are 2 ways of declaring value for optional variables,

  • Optional.of(value)
  • Optional.ofNullable(value)

What is the difference between these two?

Optional.of(“value”) will throw an exception if the value is null. Where as Optional.ofNullable will continue even if the value is null.

Internal implementation of Optional.of():
    public static <T> Optional<T> of(T value) {
        return new Optional<>(value);

    private Optional(T value) {
        this.value = Objects.requireNonNull(value);

    public static <T> T requireNonNull(T obj) {
        if (obj == null)
            throw new NullPointerException();
        return obj;

From the implementation, Optional.of(value), requires a NonNull object and will throw NullPointerException if the value is null.

Implementation of Optional.ofNullable(value):

    public static <T> Optional<T> ofNullable(T value) {
        return value == null ? empty() : of(value);

    public static <T> Optional<T> of(T value) {
        return new Optional<>(value);

From the implementation, Optional.ofNullable will return an empty Optional if the value is null. (Will not throw exception).

Filter in Optional:

Internal Implementation of Filter:

    public Optional<T> filter(Predicate<? super T> predicate) {
        if (!isPresent())
            return this;
            return predicate.test(value) ? this : empty();


Now let us see with an example,

        Optional<String> value3 = Optional.ofNullable(null);

        System.out.println(value3.filter(val -> val.contains("a"))); // condition is null

In the above example, val is null so the predicate failed.

Filtering in String,

        Optional<String> value3 = Optional.ofNullable("Alpha");

        System.out.println("Filter 1: "+value3.filter(val -> val.contains("z")));
        System.out.println("Filter 2: "+value3.filter(val -> val.contains("a")));

If the value is not available it will return an Empty Optional.


Filtering from List of String,

        Optional<List<String>> nameList = Optional.of(Arrays.asList("Alpha", "Beta", "Charlie", "Delta"));

                .filter(name -> name.contains("l")));


By Sri

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