Optional Class

What is the Optional Class?

• Introduced in Java 8, the Optional class helps handle null values gracefully, avoiding NullPointerException.

Key FeaturesWhen to Use

• Avoid Null Checks: Reduces explicit null checks.
• Functional Style: Supports map(), filter(), and ifPresent().
• Immutability: Values cannot be modified after creation.

• Use as a return type for methods that may return null.
• Avoid for fields, parameters, or collections to reduce overhead.

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Creating an OptionalCommon MethodsExample

• Empty Optional: Represents no value.

  Optional<String> empty = Optional.empty();
  System.out.println(empty.isPresent()); // false
  

• With a Value: Wraps a non-null value.

  Optional<String> optional = Optional.of("Hello");
  System.out.println(optional.isPresent()); // true
  

• With Nullable Value: Allows null values.

  Optional<String> nullable = Optional.ofNullable(null);
  System.out.println(nullable.isPresent()); // false
  

• isPresent(): Checks if a value exists.

  Optional<String> optional = Optional.of("Hello");
  System.out.println(optional.isPresent()); // true
  

• ifPresent(Consumer): Executes code if a value exists.

  Optional<String> optional = Optional.of("Hello");
  optional.ifPresent(value -> System.out.println("Value: " + value)); // Hello
  

• orElse(T): Returns the value or a default.

  Optional<String> optional = Optional.ofNullable(null);
  System.out.println(optional.orElse("Default")); // Default
  

• orElseGet(Supplier): Returns the value or invokes a supplier.

  Optional<String> optional = Optional.ofNullable(null);
  System.out.println(optional.orElseGet(() -> "Generated Default")); // Generated Default
  

• orElseThrow(Supplier): Throws an exception if no value exists.

  Optional<String> optional = Optional.ofNullable(null);
  try {
      System.out.println(optional.orElseThrow(() -> new IllegalArgumentException("Value is missing")));
  } catch (Exception e) {
      System.out.println(e.getMessage()); // Value is missing
  }
  

• map(Function): Transforms the value if present.

  Optional<String> optional = Optional.of("Hello");
  Optional<Integer> length = optional.map(String::length);
  System.out.println(length.orElse(0)); // 5
  

• filter(Predicate): Filters the value based on a condition.

  Optional<String> optional = Optional.of("Hello");
  optional.filter(value -> value.startsWith("H"))
          .ifPresent(System.out::println); // Hello
  

import java.util.Optional;

public class Main {
    public static void main(String[] args) {
        Optional<String> optional = Optional.ofNullable(getValue());

        optional.ifPresent(value -> System.out.println("Value: " + value));

        String result = optional.orElse("Default Value");
        System.out.println("Result: " + result);

        optional.map(String::toUpperCase)
                .ifPresent(System.out::println);
    }

    private static String getValue() {
        return null; // Simulates a method that may return null
    }
}