Introduction

• The Optional class in Java is a container object that may or may not contain a non-null value.
• Introduced in Java 8 to avoid NullPointerException and provide a more functional approach to handling null values.
• It is part of the java.util package.
• An Optional can either contain a value (non-empty) or be empty.
• Using Optional encourages better null-checking and cleaner code.

• Uses of Optional Class:
  • To avoid NullPointerException by explicitly handling the presence or absence of a value.
  • To provide clearer and more readable code for null-checks.
  • To use functional-style methods like map(), filter() and ifPresent() for handling optional values.

Syntax and Important Methods

• Creating Optional objects:

  // Creating an empty Optional
  Optional emptyOpt = Optional.empty();
  
  // Creating an Optional with a non-null value
  Optional valueOpt = Optional.of("Java 8");
  
  // Creating an Optional that may contain null
  Optional nullableOpt = Optional.ofNullable(getValue());

• Important Methods of Optional:
  • isPresent() - Returns true if value is present.
  • ifPresent(Consumer action) - Executes action if value is present.
  • orElse(T other) - Returns value if present, otherwise returns other.
  • orElseGet(Supplier other) - Returns value if present, otherwise invokes Supplier and returns its result.
  • orElseThrow() - Returns value if present, otherwise throws NoSuchElementException.
  • map(Function mapper) - Applies function if value is present and returns Optional of result.
  • filter(Predicate predicate) - Returns Optional if value matches predicate, otherwise empty Optional.

Program:

• Below is the program demonstrating Optional class in Java:

  import java.util.Optional;
  
  public class MainAppOptional
  {
      public static void main(String[] args)
      {
          // Creating an Optional with a non-null value
          Optional nameOpt = Optional.of("Deepak");
  
          // Checking if value is present
          if(nameOpt.isPresent()) {
              System.out.println("Value is present: " + nameOpt.get());
          }
  
          // Using ifPresent()
          nameOpt.ifPresent(name -> System.out.println("Hello, " + name));
  
          // Optional with null value
          Optional emptyOpt = Optional.ofNullable(null);
  
          // Using orElse()
          String defaultName = emptyOpt.orElse("Default Name");
          System.out.println("Value: " + defaultName);
  
          // Using map() and filter()
          Optional result = nameOpt
                  .filter(name -> name.startsWith("D"))
                  .map(name -> name.toUpperCase());
  
          result.ifPresent(System.out::println);
      }
  }

  Output:

  Value is present: Deepak
  Hello, Deepak
  Value: Default Name
  DEEPAK