CSE131 Style Guide

Getting the computer to understand your program is no guarantee that people will be able to follow it. Just as you would edit an English composition, you should spend time revising a computer program to make it elegant and readable. The following guidelines will help you write programs that are easy to read and modify. Beginning with Lab 4, the CSE131 TAs will expect your assignments to conform to these style and documentation conventions. A large portion of your lab grade is based on style, so don't assume that it's good enough to just get your program running. Read this Style Guide carefully, and let us know if you have any questions.

Completely fill out the cover-page.txt file. If you make any general assumptions regarding the problem to be solved or about the kinds of inputs your program will accept, be sure to these assumptions in a separate paragraph (labeled "ASSUMPTIONS:") at the bottom of the cover page. Deviations from the assignment should be listed as well. Keep in mind that any significant deviations should also be cleared with the instructor in advance. Specific assumptions regarding a particular method should be stated in the header comment for that method.
Before each class definition, provide a Javadoc header comment with the following information:
- Your name (and the names of any people you worked with--see the CSE131 collaboration policy)
- Your lab section (e.g., Lab E)
- Your email address
- The name of the lab assignment (e.g., CSE131 Lab 4)
- The name of the file (e.g., Vector.java)
- The date of last modification to the file.
- A brief description of the purpose of the class defined in that file.
If you have more than one class in a file, headers for subsequent classes in a file need only the brief description of the purpose of the class.
Before each method, provide a Javadoc comment that describes what the method does, and the meaning of each parameter, and its return value (if any). Eclipse will help you set this up. After typing the method header, go to the line immediately above the method header and type the characters /** and then hit the enter key. Eclipse will set up a method comment with the parameter names. Complete the header as in the following example:
```
	/**
	 * Deposits the given amount into the account.
         * REQUIRES: The given amount is positive.
	 * @param amount the dollar amount to deposit
	 * @return the new balance
	 */
	 public int deposit(int amount) {
            if (amount < 0)
               throw new IllegalArgumentException("positive amount required");
            balance += amount;
            return balance;
         }
```
In all comments, be brief and informative. Since the CSE131 TAs are already familiar with the assignment, please don't repeat the details of the assignment. Instead, communicate your approach to solving the problem.
Note: You do not need to write Javadoc comments for your JUnit test methods, but some inline comments may be necessary to explain what case the particular test is checking, if it's not immediately obvious from the test code itself.
Choose meaningful names for all variables, parameters, classes, and methods. Use complete words instead of abbreviations. For example, use width instead of w. (However, if an assignment specifies a particular name, please don't choose a different one.)
Use named constants instead of sprinkling numbers throughout your code. For example, if a paint program has a standard brush size of 5 pixels, don't just put the number 5 all over the code. Instead, define and use a constant at the top of the class, like this:
```
         static final int BRUSH_SIZE = 5;
```
This not only makes it easier to read the program, but also simplifies changing the values later because you only have to make the change in one place, where the constant is defined. (Test cases are an exception--use numbers there.) Rule of thumb: if a constant is used more than once, give it a name.
The logic of your program should be clear. Keep it simple. Avoid "clever" tricks that save a line of code at the expense of clarity.
Avoid duplicating code by writing an appropriately named procedure and calling it where neeeded.
Be especially careful to keep boolean expressions simple. This will ensure readability and will help you avoid logic errors. Also, remember to simply return the value of a boolean expression, rather than testing it in a conditional statement that returns true or false:
GOOD STYLE: BAD STYLE:
return (height >= level);
if (height >= level) return true; else return false;
Follow standard formatting conventions.

GOOD STYLE:	BAD STYLE:
return (height >= level);	if (height >= level) return true; else return false;

Capitalization:

variables and method names: the first letter is lower case, with the first letter of each subsequent word capitalized
for example, int caloriesFromFat = 18;
class names: the start of each word is capitalized
for example, public class DirectionVector {
constants: the entire name is capitalized
for example, public static final double PUPIL_FRACTION = 4;

Indentation:

braces

the open brace ({) goes at the end of the line before the start of the code block.
the close brace goes on its own line, indented to match the beginning of the line containing the corresponding open brace (an exception is "else" which goes on the same line as the closing brace for the corresponding "if", so the closing brace for the "if" doesn't appear on its own line)

code inside braces

indent one level for each level of curly braces ({})

code inside consequents

use curly braces and indent one level for consequents in conditional statements (braces may be omitted if there is only one statement in a consequent, but some editors expect the braces in order to do automatic indentation properly)

continued lines

when a statement continues across two or more lines, indent the second and remaining lines an equal amount past the start of the first line of the statement. See the example.

example:

public static boolean withdraw (int requestedAmount) {
   if (balance < requestedAmount) {
      return false;
   } else {
      balance = balance - requested amount;
      System.out.println("Withdrawl of $" + requestedAmount +
                       " successful, leaving $" +
                        balance + ".");
      return true;
   }
}

TIP: Eclipse will help correct your indentation. Select the section of the file you want to correct, and then choose "correct indentation" from the "source" menu.

Order of variables and methods within a class definition:

constants: if you define any constants, they should go first, with public constants before private ones
class variables (static variables): if you define any static variables, put them immediately after the constants, listing the public variables first
instance variables: should follow the class variables, with the public ones first
constructors: should precede all other methods
public accessors: should immediately follow the constructors
other methods, public and private: can be listed in any logical order, with related methods near each other
the toString method: should be last so people can find it quickly

Use brief inline comments whenever the meaning of the code is not immediately obvious. For example, inline comments can be useful to summarize cases in a conditional expression.

   if (xPosition < xLeft)               // left of box
      ...
   else if (xPosition > xLeft + width)  // right of box
      ...
   else if (yPosition < yBottom)        // below box
      ...
   else                                 // inside or above box
      ...

Write self-documenting code to avoid the need for inline comments. The comment in the following example adds no information and should be omitted since it just wastes the reader's time.
```
   int rectangleWidth = 30;  // the width of the rectangle is 30
```
When a CSE131 assignment asks for test cases, present your test cases clearly and methodically.
- Test cases should be ordered logically, preferably in the same order as the code being tested.
- Whenever possible, choose test cases whose expected output be quickly computed in your head (without the need for a calculator).
- When there are only a few possible inputs, test them all. Otherwise, choose test cases that exercise all branches of the code (for example, one test case that satisfies the condition in an if statement and a second test case that doesn't satisfy the condition).
- Be thorough. Pretend that you are an adversary trying to "trick" the program into giving the wrong answer. For example, test cases should include zero or negative values even if the "normal" case is a positive number. However, you are not obligated to test inputs that violate your stated assumptions.
Be professional. Use the same care in preparing your code as you would for any writing assignment. Avoid jokes in your code, slang terms, crude comments, etc.

Use common sense. Remember that the CSE131 style guide is only a guide. Your primary concern should be making sure that others can read and understand the text of your program. If you think an additional comment or particular organization will get your ideas across more effectively, do it. However, if you are considering deviating significantly from the guidelines or if you are in doubt about something, discuss it with us first.