Method References & Optional
Learn Java method references and the Optional class.
Method References & Optional is a free Java Academy lesson on CoddyKit — lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Intro
Method references are a shorthand for lambdas that call an existing method. Optional helps handle missing values safely.
Syntax
Syntax: ClassName::methodName or object::methodName. It replaces a lambda that just calls that method.
Code: method reference
This uses System.out::println as a method reference to print each name.
import java.util.*;public class Main {
public static void main(String[] args) {
List<String> names = Arrays.asList("Ada", "Bob", "Eve");
names.forEach(System.out::println);
}
}
Optional basics
Optional<T> is a container that may or may not hold a value. It helps avoid null pointer errors.
Code: Optional
This wraps a string in Optional and prints it if present.
import java.util.Optional;public class Main {
public static void main(String[] args) {
Optional<String> opt = Optional.of("Hello");
if (opt.isPresent()) {
System.out.println(opt.get());
}
}
}
Code: ifPresent
Optional.ifPresent accepts a lambda to act only if a value exists.
import java.util.Optional;public class Main {
public static void main(String[] args) {
Optional<String> opt = Optional.of("World");
opt.ifPresent(v -> System.out.println("Value: " + v));
}
}
Method reference check
Quick check: Which symbol is used for method references?
Recap
Recap: Method references are shorthand for simple lambdas. Optional stores a value safely and avoids nulls.
Frequently asked questions
Is the “Method References & Optional” lesson free?
Yes — the full text of “Method References & Optional” is free to read here on the web, and the Java Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO.
What will I learn in “Method References & Optional”?
Learn Java method references and the Optional class. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Method References & Optional” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Lambda Syntax & Scope
- Functional Interfaces
- Method References & Optional