Oracle's Code Conventions for the Java Programming Language | Generated by AI

Home PDF English 中文 日本語 Español हिंदी Français Deutsch العربية 繁體中文

---

1. File Organization

1.1 File Names

• Source files must have the .java extension
• Source filenames must exactly match the public class name in the file
• Examples:
  • MyClass.java contains a public class named MyClass
  • CircleShape.java contains a public class named CircleShape

1.2 File Structure

1. Beginning comments
2. Package statement
3. Import statements
4. Class and interface declarations

2. Formatting and Indentation

2.1 Indentation

• Use 4 spaces for indentation (not tabs)
• Indent continuation lines by 8 spaces
• Braces should align vertically

2.2 Line Length

• Recommended maximum line length is 80 characters
• For long statements, break lines at a higher logical level

2.3 Wrapping Lines

• Break line before an operator
• Align the new line with the beginning of the expression at the same level

3. Comments

3.1 File Comments

• Every source file should start with a comment block: ```java /*
  • Classname
  • Version information
  • Date
  • Copyright notice */ ```

3.2 Implementation Comments

• Use /* */ for multi-line comments
• Use // for single-line comments
• Comments should explain “why”, not “what”

3.3 Documentation Comments

• Use Javadoc-style comments for classes, interfaces, methods
• Include:
  • Brief description
  • @param for method parameters
  • @return for return values
  • @throws for exceptions

4. Declarations

4.1 Number Per Line

• One declaration per line
• Recommended:

  int level;        // Correct
  int size;         // Correct
    
  // Avoid:
  int level, size;  // Not recommended
  

4.2 Initialization

• Initialize variables at declaration when possible
• Group related declarations together

5. Statements

5.1 Simple Statements

• One statement per line
• Use a space after commas
• Use spaces around operators

5.2 Compound Statements

• Braces are used with if, else, for, while, do statements, even for single-line blocks

5.3 Return Statements

• Prefer explicit return
• Avoid unnecessary else after return

6. Naming Conventions

6.1 Package Names

• All lowercase
• Unique prefix, often company domain reversed
• Example: com.company.project

6.2 Class Names

• UpperCamelCase
• Noun or noun phrases
• Examples: DataProcessor, HttpClient

6.3 Interface Names

• Similar to class names
• Consider describing behavior
• Examples: Runnable, Serializable

6.4 Method Names

• lowerCamelCase
• Verb or verb phrases
• Examples: calculateTotal(), sendMessage()

6.5 Variable Names

• lowerCamelCase
• Meaningful and descriptive
• Avoid single-letter names except for temporary variables

6.6 Constant Names

• ALL_UPPERCASE with underscores
• Example: MAX_VALUE, COLOR_RED

7. Programming Practices

7.1 Visibility

• Use the lowest possible visibility
• Prefer private over public
• Use accessor methods for class fields

7.2 Variable Scope

• Declare variables in the smallest scope possible
• Initialize variables close to their first use

7.3 Exception Handling

• Always include a message in exceptions
• Catch specific exceptions
• Use try-catch-finally appropriately

8. Best Practices

8.1 Avoid Magic Numbers

• Use named constants instead of literal numbers
• Improve code readability and maintainability

8.2 Prefer Immutability

• Use final for variables that don’t change
• Create immutable classes when possible

Conclusion

These conventions aim to improve code readability, maintainability, and consistency across Java projects.

---

Back 2025.03.29 Donate