Java 9 Optional Class Improvements

Optional class is introduced in Java 8 to prevent the null checks and NullPointerException. Before Java 8, if-constructs are used to check the null values. But, it is not an perfect way to check for null value as it doesn’t resolve NullPointerException although it just hides it and propagates it to the next level. Therefore, inspired by other functional programming languages, Optional class is introduced in Java to handle the null values from Java 8.

Java 9 Optional Class Improvements :

of(), empty(), ofNullable(), get(), ifPresent(), isPresent(), orElse(), orElseGet(), orElseThrow(), map(), flatMap() and filter() are the methods of Java 8 Optional class. Three more methods are added to Optional class from Java 9. 

three new methods are added to improve its functionality.

• stream()
• ifPresentOrElse()
• or()

 Let’s see these methods in detail.

ifPresentOrElse() Method :

This method performs the given action if the value is present in the Optional object. If the value is absent, performs the given empty-based action.

You can use this method when you want to perform different actions depending upon the presence and absence of a value.

import java.util.Optional; public class Java9OptionalImprovements {     public static void main(String[] args)    {         //Optional object with a value                   Optional<String> optionalAddress_1 = Optional.of("Address_1");                   optionalAddress_1.ifPresentOrElse(address -> System.out.println("Address : "+address), () -> System.out.println("No Address"));                   //Optional object without a value                   Optional<String> optionalAddress_2 = Optional.empty();                   optionalAddress_2.ifPresentOrElse(address -> System.out.println("Address : "+address), () -> System.out.println("No Address"));     } }

Output :

Address : Address_1
No Address

or() Method :

This method returns an Optional object containing the value if the value is present in the given Optional object. If the value is not present, it returns an Optional produced by the supplying function.

This method is similar to orElse() and orElseGet() which return unwrapped value where as this method returns the value wrapped in another Optional.

import java.util.Optional;   public class Java9OptionalImprovements {     public static void main(String[] args)     {         //Optional object with a value                   Optional<String> optionalAddress_1 = Optional.of("Address_1");                   Optional<String> optional = optionalAddress_1.or(() -> Optional.of("No Address"));                   System.out.println(optional.get());                   //Optional object without a value                   Optional<String> optionalAddress_2 = Optional.empty();                   optional = optionalAddress_2.or(() -> Optional.of("No Address"));                   System.out.println(optional.get());     } }

Output :

Address_1
No Address

stream() Method :

This method returns a stream containing the value if the value is present in the given Optional object. If the value is not present, it returns an empty stream.

This method converts Optional into Stream and enables the developers to use all operations of Stream API with an Optional object also.

import java.util.Optional;   public class Java9OptionalImprovements {     public static void main(String[] args)     {         //Optional object with a value                   Optional<String> optionalAddress_1 = Optional.of("Address_1");                   optionalAddress_1.stream().forEach(System.out::println);                   //Optional object without a value                   Optional<String> optionalAddress_2 = Optional.empty();                   optionalAddress_2.stream().forEach(System.out::println);     } }

Output :

Address_1