Style Guide (Checkstyle)

Source: https://xkcd.com/1513/

Background

Virtually every organization that does software development has strict guidelines on how to format source code. Here are two examples of "industrial strength" Java style guides:

• Code Conventions
• Google Java Style

This course will follow a simplified version of these guidelines. We hope you will focus on developing good habits and intuition about style, rather than memorizing a long list of rules.

Source: https://checkstyle.sourceforge.io/

Checkstyle is a tool (integrated into VS Code) that can be used to determine if your source code follows a set of style rules. Checkstyle also checks for common programming mistakes, such as empty statements and accidental assignment.

A. Comments

1. Every class must contain a Javadoc comment with the following three elements.

/**
  * Overall description of the class goes here.
  *
  * @author Your name goes here
  * @version Due date goes here
  */

2. All methods (including main) must contain an applicable Javadoc comment.

/**
 * Overall description of the method goes here.
 *
 * @param parameterName describe each input parameter
 * @param anotherParam use a separate line for each
 * @return describe the value that this method returns
 */

3. In-line comments (//) should describe major structures and steps within a method.

4. All comments should use normal English spelling and grammar. Phrases are okay.

5. Comments must come before the code that they are describing or on the same line.

B. Names

1. All names should be descriptive and readable.
   (subTotal rather than s, grade rather than grd)

2. Multiple-word names should use capital letters to separate words.
   (subTotal, not sub_total)

3. Variable and method names should begin with a lowercase letter, and:

   • Variable names should be nouns or noun phrases.
     (studentName or subTotal)

   • Method names should be verbs or verb phrases.
     (printLine or addColumn)

4. Class names should begin with a capital letter and use title case.
   (HelloWorld)

5. Constant names should be all caps with an underscore separator.
   (PI or INTEREST_RATE)

C. Declarations

1. All constants should be named and initialized at the top of the method in which they are used.

   final double CENTIMETERS_PER_INCH = 2.54;
   centimeters = inches * CENTIMETERS_PER_INCH;    // NOT inches * 2.54;
   

2. All variables should also be declared at the top of the method, directly after any constant declarations.

3. It is recommended (in CS 159) to separate variable declaration and initialization statements.

   Scanner input = new Scanner(System.in);    // discouraged
   
   Scanner input;
   input = new Scanner(System.in);
   

4. Each declaration should be on its own line. Comment to the right if the name is not self-explanatory.

D. Literals

1. Numeric literals should be of the correct type for the context in which they are used.

// integer expressions should use integer literals
int a;
double b;
a = 2;
b = 2.0;

// double expressions should use double literals
double x;
double y;
double average;
average = (x + y) / 2.0;    // NOT 2, which is an integer

E. Indentation

1. Subsections of code should be indented consistently with four spaces.

2. Always use four space characters, not tab characters, for indentation.

3. Statements too long for one line should be indented on subsequent lines.

4. All blocks of code (even if one line) should be surrounded by curly braces.

5. Left braces must appear at the end of the same line as the structure header.

F. Whitespace

1. There should be a space after cast operators, commas, and //'s.

2. Use whitespace to separate logical segments of code. There should be a blank line after variable declarations.

3. Lines should be kept to a short length (< 80 chars). You should be able to see the full line in your text editor.

4. Binary operators should be separated from their operands by a single space.
   (sum = myGrade + yourGrade;)

5. The dot (.) operator, on the other hand, should not have any space surrounding it.
   (System.out.println();)

6. Unary operators should also not be separated by a space.
   (myGrade++;)