Java: Identifiers and Data Types

1. Identifiers

• Identifiers are the names you give to:
  • Variables
  • Classes
  • Methods
  • Packages
  • Constants
  • Interfaces, Enums, Annotations, Records

🎯 Good identifier choice is critical! It affects clarity, maintainability, and teamwork!

Rules for Java Identifiers:

• Must start with a letter (A-Z, a-z), underscore (_) or dollar sign ($).
• Subsequent characters can be letters, digits (0-9), underscore, dollar sign.
• Cannot be a Java reserved word (e.g., class, public, void, etc.).
• Should be meaningful, even if it takes longer to think of a good name.

Best Practices:

• Class names: Start with uppercase (e.g., Person, OrderSystem).
• Variable and method names: Start with lowercase, use camelCase for multiple words (e.g., userName, calculateTotal()).
• Constants: All UPPERCASE_WITH_UNDERSCORES (e.g., MAX_SIZE).
• Packages: all lowercase (e.g., utilities.math).

2. Primitive Data Types

Java has 8 primitive types, divided into 4 categories: