Module 9: Exceptions, Validation, and Debugging

Try-with-Resources and AutoCloseable

Use try-with-resources so files, scanners, and streams close automatically.

Author

Java Learner Editorial Team

Reviewer

Technical review by Java Learner

Last reviewed

2026-04-17

Java version

Java 25 LTS

How this lesson was prepared: AI-assisted draft, manually edited for clarity, and checked against current Java documentation and runnable examples.

Learning goals

Try-with-resources is the default for files, readers, streams, and scanners: It closes resources automatically when the block ends.

This is cleaner than manual finally cleanup: The code is shorter, safer, and harder to get wrong.

The resource must implement AutoCloseable: Many core Java IO and database classes already do.

Practical rule: If you opened something that needs closing, try-with-resources should be your first move.

Runnable examples

Scanner closes automatically

import java.util.Scanner;

try (Scanner scanner = new Scanner("Ada\n")) {
    System.out.println(scanner.nextLine());
}

Expected output

Ada

Mini exercise

Use try-with-resources with a `Scanner` that reads from a string, then print the first token.

Summary

Next step

Next, design custom exceptions that carry meaning instead of throwing generic failures everywhere.

Sources used