Java Syntax Style Rules

Why are Coding Style Rules Important?

• 80% of the lifetime cost of a piece of software goes to maintenance.
• Hardly any software is maintained for its whole life by the original author.
• Coding conventions make code easier to read, debug, and modify (both for the author and for others).
• If you you ship code as a product, it should be clean and "well engineered".

Coding Style Guidelines

1. Avoid "The Blob".
   "The Blob" is what happens when a lot of complex code is put into one class, potentially all within one method. If code is complex, break up it up into several classes and/or methods.


2. Use comments
   Put a comment above every class and non-trivial method. Ideally, javadoc comments (beginning with /** and ending with */) should be used for all classes, methods, and variables that are not private.


3. Identifier Naming Conventions
   • Use meaningful names (Exception: temporary variables such as integer counters are often named i, j, and k.)

   Kind	Par-of-Speech	Identifier Examples
   Variable	noun	sum, intialSpeed, firstName
   Constant	noun	SPEED_OF_LIGHT, PI

4. Number of statments per line
   • One line per statement is ideal for clarity
   • It it easier to describe what the statement is doing and encourage commenting per line
   • Example:

        int heightInFeet = 5; //height in feet
        double heightInInches = 2.54 * heightInFeet; //convert height from feet to inche
   	   

5. Spacing Conventions
   • You should put a single space around every operator, including comparisons and equality
   • Example: perimeter=2*(width+height);
   • Do not put spaces just inside parentheses:perimeter = 2 * (width + height); //bad


6. Indent properly and keep the length of all lines <= 80 characters
   • Any statements contained within another statement should be indented. Indentation should consist of 2-4 spaces (3 or 4 is usually best), and should be consistent throughout
   • The line length should not exceed 80 characters; other developers may find your code annoying to work with if it does.

   Be aware that if an editor other than DrJava is used, using tabs may be problematic. An editor (e.g. NotePad) may replace tabs with 8 spaces. If a tab is replaced with more than 4 spaces your code may be hard to read and difficult for another developer to work with. Check your editor/IDE to see if tab behavior is a configurable option.

   
   
7. Choose a style for curly braces and stick to it within a source file/package.
   The two most common ways of using curly braces are:

  if (x == y) {  	
	statements 
  }	
  OR 
  if (x == y)  	
  {  	   
 	statements 	
  }   
  

8. Methods
• Use the DRY principle: Don't Repeat Yourself. If you find yourself writing the same or similar code two or more times, consider whether it could be put into a separate method.
• Give methods names that are verbs. The first word should begin with a lowercase letter. For multiword names, each new word should be capitalized. Examples: display(...), computeTotal(...).
• If there is a "primary" method, make it "short & sweet". For example, the main method in a simulation should only be a few lines long - a few initialization steps, a loop with some method calls, and some method calls to wrap things up.


9. Classes
• Give classes names that are capitalized nouns
• For multiword names, each new word should be capitalized. Examples: Counter, Ticket, DormRoom .
• Organize variables and methods within a class as recommended by Sun: First static variables, then dynamic/instance variables, then constructors, then methods grouped by functionality.

"Official" Java Coding Conventions from Sun

• Other style rules may be mentioned throughout the course.
• Java Coding Convention

Important about style rules

• These are not Java coding style rules
• If you break these rules, your program will still compile.
• This is done so that your code is readable and clear.
• If you do not follow the rule you get penalized in grading!