java-best-practices

name	java-best-practices
description	Java coding best practices. Use when writing or reviewing Java code (17+). Covers modern features, error handling, and patterns.
license	MIT
metadata	{"author":"plan-cascade","version":"1.0.0"}

Java Best Practices (17+)

Code Style

Rule	Guideline
Formatter	google-java-format
Analysis	SpotBugs, Error Prone
Naming	Clear, no abbreviations

Modern Features

Feature	Usage
Records	Immutable data carriers
Sealed classes	Restricted hierarchies
Pattern matching	instanceof with binding
var	Local type inference

public record User(String id, String name) {}

if (obj instanceof String s && !s.isEmpty()) { process(s); }

public sealed interface Result<T> permits Success, Failure {}
record Success<T>(T value) implements Result<T> {}
record Failure<T>(Exception error) implements Result<T> {}

Error Handling

Rule	Guideline
Specific exceptions	Not bare Exception
Try-with-resources	For AutoCloseable

try (var reader = new BufferedReader(new FileReader(path))) {
    return reader.lines().toList();
} catch (IOException e) {
    throw new ConfigException("Failed: " + path, e);
}

Project Structure

src/main/java/com/example/{domain,service}/
src/test/java/
pom.xml or build.gradle

Common Patterns

Pattern	Usage
Optional	Null-safe returns
Stream API	Functional collections
Builder	Complex construction

public Optional<User> findById(String id) {
    return Optional.ofNullable(users.get(id));
}

Anti-Patterns

Avoid	Use Instead
Returning null	Optional<T>
Mutable data	Records
instanceof chains	Pattern matching

Testing (JUnit 5 + AssertJ)

@Test void shouldProcess() {
    var service = new Service(mockRepo);
    var result = service.process(input);
    assertThat(result.status()).isEqualTo(SUCCESS);
}