Java Coding Standards

Java Coding Standards

When reviewing or generating Java code, follow these rules:

File Naming

• Source files: PascalCase matching the public class name (e.g., UserService.java)
• One public class per file: File name must match the public class name exactly
• Test files: Class name with Test suffix (e.g., UserServiceTest.java)
• Interface files: PascalCase (e.g., Comparable.java, UserRepository.java)

Package Naming

• Packages: All lowercase, dot-separated (e.g., com.example.service, org.project.utils)
• No underscores or hyphens in package names
• Follow reverse domain name convention

Variable Naming

• Local variables: camelCase (e.g., userName, isActive, totalCount)
• Instance variables: camelCase (e.g., userId, createdAt)
• Constants: UPPER_SNAKE_CASE with static final (e.g., MAX_RETRIES, DEFAULT_TIMEOUT)
• Boolean variables: Prefix with is, has, can, should (e.g., isEnabled, hasPermission)

Method Naming

• Methods: camelCase, verb or verb phrase (e.g., calculateTotal(), getUserById())
• Getters: get prefix (e.g., getName(), getId())
• Setters: set prefix (e.g., setName(), setId())
• Boolean getters: is or has prefix (e.g., isActive(), hasChildren())
• Factory methods: create, of, from, valueOf (e.g., createInstance(), of())

Class/​Interface Naming

• Classes: PascalCase, noun or noun phrase (e.g., UserService, OrderProcessor)
• Interfaces: PascalCase, adjective or noun (e.g., Comparable, UserRepository)
• Abstract classes: PascalCase, optionally prefix with Abstract (e.g., AbstractHandler)
• Exception classes: PascalCase with Exception suffix (e.g., InvalidInputException)
• Enums: PascalCase for type, UPPER_SNAKE_CASE for values

Generics

• Type parameters: Single uppercase letter (e.g., T, E, K, V)
• Meaningful names: When clarity needed (e.g., <Key, Value>)

Organization

• Package statement first
• Import statements (java., javax., third-party, project imports)
• Class declaration with fields, constructors, methods
• Public methods before private methods