Style Jan 16 2019 Why style matters Good style isn t just to make your code look pretty The most critical factor in style is readability If a program is readable It is easier to debug It is easier to maintain It is easier to upgrade For real programs those that actually get used the time spent reading them far exceeds the time spent writing them 2 Two kinds of style Syntactic style Mostly pretty mechanical Spacing indentation capitalization etc Eclipse can do a lot of this for you Some more conceptual for example the names of methods should be verbs Syntactic style is easier to define Semantic style Largely or completely non mechanical Rules are slippery harder to describe and to apply Learned largely through experience But only if you are willing to experiment and try new approaches Ultimately much more important than syntactic style 3 Syntactic style Be consistent Most times you will enter an ongoing project with established style rules Follow them even if you don t like them As they are what your team is used to they will be more readable to other members of your team 5 Do it right the first time You only write code once but you read it many times while you re trying to get it to work Good style makes it more readable and helps you get it right You re working on a large project so you use good style but you need a tool to help you do one little job so you slap it together quickly Guess which program will be around longer and used by more people 6 Indent nested code Always indent statements that are nested inside under the control of another statement if itemCost bankBalance writeCheck itemCost bankBalance bankBalance itemCost The open brace always goes at the end of a line The matching close brace lines up with the statement being closed Don t use C style braces unless that is the already established standard for the project you are on Indentation should be consistent throughout the program 4 spaces is the standard for Java other languages may differ 7 Break up long lines Keep your lines short enough to be viewed and printed Many people use 72 or 80 character limits Suggestions on where to break a long line It s illegal to break a line within a quoted string Break after not before operators Line up parameters to a method Don t indent the second line of a control statement with a long test so that it lines up with the statements being controlled 8 Don t use hard tabs A hard tab is an actual tab character in your text It tells the program to go to the next tab stop wherever that is Not every program puts tab stops in the same place If you use hard tabs to indent sooner or later your nice indentation will be ruined Good editors can be set to use soft tabs your tab characters are replaced with spaces When you hit the tab key the editor puts spaces into your file not tab characters With soft tabs your indentation is always safe 9 Using spaces Use spaces around all binary operators except dot if n 1 n 2 1 n 3 n 1 Do not use spaces just within parentheses if x 0 x x don t do this Use a space before and after the parenthesized test in a control statement if x 0 while x 0 Do not use a space between a method name and its parameters do put a space after each comma int add int x int y a add 3 k 10 Use meaningful names Names should be chosen very carefully to indicate the purpose of a variable or method If the purpose changes the name should be changed Spend a little time to choose the best name for each of your variables and methods Long multiword names are common in Java Eclipse will complete long names for you control space However if a name is too long maybe you re trying to use it for too many purposes Don t change the name separate the purposes Don t abbreviate names But very common abbreviations such as max for maximum are OK 11 Meaningful names exceptions I It is common practice to use i as the index of a forloop j as the index of an inner loop and k as the index of a third level loop This is almost always better than trying to come up with a meaningful name Example for int i 1 i 10 i for int j 1 j 10 j System out println i j 12 Meaningful names exceptions II Local variables in methods may be given short simple names if The purpose of the variable is obvious from context and The variable is used only briefly in a small part of the program But never use meaningless names for fields class or instance variables or classes or methods 13 Meaningful names exceptions III If variables have no special meaning you can use names that reflect their types For example if you are writing a general method to work with any strings you might name them string1 string2 etc Alternatively you can use very short names s t u or s1 s2 etc are often used for Strings p q r s are often used for booleans w x y z are often used for real numbers 14 Naming classes and interfaces Capitalize the first letter of each word including the first word PrintStream Person ExemptEmployee Use nouns to name classes ExemptEmployee CustomerAccount Classes are supposed to represent things Use adjectives to name interfaces Comparable Printable Interfaces are supposed to represent features 15 Naming variables Capitalize the first letter of each word except the first total maxValue Use nouns to name variables balance outputLine Variables are supposed to represent values 16 Naming methods Capitalize the first letter of each word except the first display displayImage Methods are capitalized the same as variables Use verbs when naming methods displayImage computeBalance Methods are supposed to do something 17 Naming constants A constant is an identifier whose value once given cannot be changed Constants are written with the keyword final for example final int FIVE 5 final float AVOGADROS NUMBER 6 022E23 Constants are written in ALL CAPITALS with underscores between words 18 Correct syntactic style made easy In Eclipse go to Window Preferences Java Code Style Formatter and under Select a profile choose Java conventions built in Select some or all of your code and choose Source Format To simply indent correctly without reformatting select some lines and choose Source Correct Indentation or just type ctrl I 19 Semantic Style Think small According to world famous computer scientist Edgser Dijkstra We have small heads Translation We can only keep track of a few things at a time Small single purpose methods are much easier to read write and debug Difficulty goes up with the square of the length of the method Think of each method as a verb
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