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Java 8 Features > Stream API > Optional Class

Optional Class

Author: Venkata Sudhakar

Java 8 introduced the Optional class to handle null values gracefully and avoid NullPointerException. It acts as a container object that may or may not contain a non-null value.

Key Optional Methods:

1. Optional.of(value) - Creates an Optional with a non-null value.

2. Optional.ofNullable(value) - Creates an Optional that may hold null.

3. Optional.empty() - Creates an empty Optional.

4. isPresent() - Returns true if value is present.

5. orElse(default) - Returns value or default if empty.

The below example shows how to use Optional to avoid NullPointerException.

import java.util.Optional;

public class OptionalExample {
    public static void main(String[] args) {
        // 1. Basic Optional creation
        Optional<String> name = Optional.of("Alice");
        Optional<String> empty = Optional.empty();
        Optional<String> nullable = Optional.ofNullable(null);

// 2. Check and get value
        System.out.println("Name present: " + name.isPresent());
        System.out.println("Name value: " + name.get());
        System.out.println("Empty present: " + empty.isPresent());

// 3. orElse - provide default
        String result1 = empty.orElse("Default Name");
        System.out.println("orElse: " + result1);

// 4. orElseGet - lazy default via supplier
        String result2 = nullable.orElseGet(() -> "Generated Default");
        System.out.println("orElseGet: " + result2);

// 5. map - transform if present
        Optional<Integer> nameLength = name.map(String::length);
        System.out.println("Name length: " + nameLength.orElse(0));

// 6. filter - conditional check
        Optional<String> longName = name.filter(n -> n.length() > 3);
        System.out.println("Long name: " + longName.orElse("too short"));

// 7. ifPresent - action if value exists
        name.ifPresent(n -> System.out.println("Hello, " + n + "!"));

// 8. orElseThrow - throw exception if empty
        try {
            empty.orElseThrow(() -> new RuntimeException("No value present!"));
        } catch (RuntimeException e) {
            System.out.println("Caught: " + e.getMessage());
        }
    }
}

It gives the following output,

Name present: true
Name value: Alice
Empty present: false
orElse: Default Name
orElseGet: Generated Default
Name length: 5
Long name: Alice
Hello, Alice!
Caught: No value present!

Best Practices for Optional:

1. Never use Optional.get() without isPresent() - use orElse() or orElseThrow() instead.

2. Do not use Optional as method parameter - use it as return type only.

3. Do not use Optional for class fields - it is not Serializable.

4. Prefer ifPresent() or map() over explicit null checks for cleaner code.

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