Module Review

In this module, we explored the modern features of Java that make code more concise, secure, and functional:

  1. Records: Using immutable data carriers to eliminate boilerplate like getters, equals(), and hashCode().
  2. Sealed Classes: Restricting inheritance to a specific set of permitted subclasses for better domain modeling and security.
  3. Pattern Matching: Leveraging instanceof patterns and switch expressions to remove explicit casting and handle complex type-based logic.
  4. Functional Interfaces: Understanding how Lambdas and Method References implement single-method interfaces to enable functional programming.

1. Flash Quiz

1. Are the fields in a Java Record mutable or immutable?

  • They are final (immutable) by default.

2. Which keyword is used in a switch expression to return a value from a multi-line code block?

  • yield.

3. What is the requirement for an interface to be considered a “Functional Interface”?

  • It must have exactly one abstract method.

4. How does a Sealed Class help with “Exhaustiveness” in a switch expression?

  • Since the compiler knows exactly which classes can extend a sealed class, it can verify that a switch covers all possible cases, removing the need for a default case.

5. Convert this lambda to a method reference: s → s.toLowerCase()

  • String::toLowerCase.

2. What’s Next?

Advanced OOP is the syntax, but how do we process collections of data efficiently? In the next module, we move to Streams and Lambdas, where we learn how to use functional pipelines to filter, map, and reduce data with extreme readability and performance.