Style

Guidelines to aid code understanding.

1. Limits
2. Names
3. Whitespace
4. Comments
5. Sample class

Programming is an inherently collaborative activity, so it is important to know how to write code that is easily understood by other people. Code style refers to programming guidelines that can help programmers read and understand code. This page describes the core guidelines that we will use in this course.

Most formatting-related style guidelines can be detected automatically using the style checker. To install the style checker, go to File | Settings | Plugins and then install the “CS 61B” plugin. To run the style checker, right-click on a file in the project tool window and select Check Style. This will generate a list of style errors in the selected file. You can also right-click the entire src folder to run the style checker on all source files.

The style checker does not check for descriptive variable names or comments. If you make a change in IntelliJ, the style checker requires files to be manually saved using Ctrl+S to recognize your changes.

Limits

No line may be longer than 120 characters.

No method may have more than 8 parameters.

Every file must contain exactly one outer class (nested classes are OK).

Names

In general, use descriptive variable names that explain the variable’s purpose and meaning. For simple loop variables, it is fine to use brief names such as i, j, k. Avoid “magic numbers” in code by using descriptive names and defining them as private static final constants at the top of the class. Only the following numbers can be entered directly: -1, 0, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9.

static final constants

Name them in all capitals, such as RED or DEFAULT_NAME.

Parameters, local variables, and methods

Names start with a lowercase letter or consist of a single, uppercase letter, such as maxLength, N, index, getWidth.

Classes and interfaces

Names start with a capital letter such as SampleClass or LinkedList.

Whitespace

The basic indentation step is 4 spaces. Don’t use tab characters for indentation. Indent code by the basic indentation step for each block.

Remove trailing blank spaces from the end of a line.

Each file must end with a newline sequence (aka a blank line).

Comments

Each class should have Javadoc comments briefly explaining the purpose of the class with @author and @since tags.

Each method should have Javadoc comments explaining the behavior, parameters (using @param tags), return type (using @return tag), and exceptions thrown (using @throws tag).

Sample class

The following sample class showcases a program that follows most of the style guidelines (aside from descriptive variable names).

import java.lang.IndexOutOfBoundsException;

/**
 * Description of Sample Class.
 *
 * @author First Last
 * @since Date
 */
class SampleClass {

    // Avoid magic numbers by declaring private constants.
    private static final int MAX_SIZE = 100;

    private int instanceVariable;

    /**
     * Description of constructor.
     *
     * @param para Description of para
     */
    public SampleClass(int para) {
        instanceVariable = para;
    }

    /**
     * Description of method.
     *
     * @param para1 Description of para1
     * @param para2 Description of para2
     * @return Description of return value
     * @throws IndexOutOfBoundsException when this exception is thrown
     */
    public int sampleMethod(int para1, int para2)
            throws IndexOutOfBoundsException {
        ...
    }
}