How to use Optional in Java 8

Category : Java | Sub Category : Java 8 Features | By Prasad Bonam Last updated: 2020-10-01 03:53:59 Viewed : 682

Java 8 Optional

/* @since 1.8

 */

public final class Optional<T> { }

java.util.Optional<T>

A container object which may or may not contain a non-null value. If a value is present, isPresent() will return true and get() will return the value.
Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (return a default value if value not present) and ifPresent() (execute a block of code if the value is present).
This is a value-based class; use of identity-sensitive operations (including reference equality (==), identity hash code, or synchronization) on instances of Optional may have unpredictable results and should be avoided.

Advantages of Java 8 Optional:

Java 8 Optional Example:

Java8OptionalEx.java 

import java.util.ArrayList;
import java.util.List;
import java.util.Optional; 
public class Java8OptionalEx {
     public static void main(String args[]) {
           // Basic Optional orElse method
    Optional<String> animal = Optional.of("Dog");          
    Optional<String> emptyStr = Optional.empty();
System.out.println("animal.orElse " + animal.orElse(" "));//Dog  
System.out.println("emptyStr.orElse " + emptyStr.orElse("N/A"));//N/A 
System.out.println("animal.orElseGet "+animal.orElseGet(()->""));//Dog
System.out.println("emptyStr.orElseGet "+emptyStr.orElseGet(() -> "N/A"));//N/A

   // Optional isPresent and ifPresent
if (animal.isPresent()) {
   System.out.println("animal.isPresent() " + "Animal is present."); 
} else {         
System.out.println("Animal not present.");     
}

/** ifPresent */
animal.ifPresent(a -> System.out.println("animal.ifPresent " + " animal Option available."));
// if condition failed
emptyStr.ifPresent(a -> System.out.println("emptyStr.ifPresent " + "emptyStrOption available."));

 /**Returns an Optional with the specified present non-null value. **/ 
Address address = new Address("1-22,Srinagar, "Hyder","India",56001);
Employee emp1 = new Employee("Ram", Optional.of(address), 111);
Employee emp1 = new Employee("Meera", Optional.empty(), 999);
Employee emp2 = new Employee("Shyam", Optional.empty(), 555);
List<Employee> people = new ArrayList<>();
           people.add(emp);
           people.add(emp1);
           people.add(emp2);
people.stream().forEach((p) -> { System.out.printf("%s stay %s %n", p.name(), p.address().orElse(Address.EMPTY_ADDRESS));

 }); 
}}

Pojo Class 1:   Employee.java  

 class Employee {

Pojo class 2: Address.java  

 class Address {

OutPut:

    animal.orElse Dog

    emptyStr.orElse N/A

    animal.orElseGet Dog

    emptyStr.orElseGet N/A

    Ram stay Address{addreLine=1-22 ,Srinagar, city=Hyder, country=India, zipcode=56001} 

    Meera stay Address{addreLine=, city=, country=, zipcode=0} 

    Shyam stay Address{addreLine=, city=, country=, zipcode=0} 

    animal.isPresent() Animal is present.

    animal.ifPresent  animal Option available.