Java Style Guide - Quick Reference

Based on Google Java Style Guide

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1. File & Class Structure

• File name = Class name:

  public class CustomerOrder { ... }

• Class naming: UpperCamelCase

• Package naming: alllowercase

• Member order: Constants → Fields → Constructors → Methods → Inner Classes

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2. Indentation & Formatting

• Indent: 2 spaces (no tabs)
• Max line length: 100 chars
• Braces: Same line, always use braces

if (condition) {
  doSomething();
} else {
  doSomethingElse();
}

• Whitespace:

  • Single space after keywords: if (x > 0)
  • No space between method name and parentheses: calculateTotal()

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3. Naming Conventions

Type	Style	Example
Class/Interface	UpperCamelCase	CustomerOrder
Method/Variable	lowerCamelCase	calculateTotal()
Constant	UPPER_SNAKE_CASE	MAX_SIZE
Package	lowercase	com.example.project

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4. Comments

• Javadoc for public APIs:

/**
 * Calculates total.
 * @param qty Number of items
 * @param price Price per item
 * @return Total cost
 */
public double calculateTotal(int qty, double price) { ... }

• Inline: // short explanation
• Block: /* multi-line explanation */

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5. Best Practices

• Use final when possible
• Avoid magic numbers → use constants
• Prefer standard library (Collections, Streams, Optional)
• Catch specific exceptions only
• Minimize null → prefer Optional

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6. Testing

• Unit tests for all public methods
• Descriptive test names: calculateTotal_givenValidInput_returnsCorrectSum()
• Use AAA pattern: Arrange → Act → Assert

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7. Annotations

• @Override when overriding
• @Deprecated with comment
• @SuppressWarnings only if necessary, document why

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8. Version Control

• Meaningful commit messages: Fix null pointer in calculateTotal
• Small, focused commits
• Merge after code review and passing tests

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Reference

Google Java Style Guide