Style Rules II Names and Naming Overview Today we will discuss Reasons for naming conventions Rules for naming variables classes and methods Why have naming conventions A program is written once but read many times During debugging When adding to the program When updating the program When trying to understand the program Anything that makes a program more readable and understandable saves lots of time even in the short run Rule 9 Use meaningful names Names should be chosen very carefully to indicate the purpose of a variable or method If the purpose changes the variable or method should be renamed It is worthwhile spending a little time choosing the best name Long multiword names are common in Java Rule 10 Use familiar names Where common terminology exists use it don t make up your own Example from the book If your users refer to customers your program should use the name Customer not Client Rule 11 Question excessively long names Variables should be used for a single purpose Methods should do one simple clearly defined thing If a descriptive name is overly long maybe the variable or method is trying to serve too many purposes Meaningful names exceptions I It is common practice to use i as the index of a for loop j as the index of an inner loop and k as the index of a thirdlevel 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 Meaningful names exceptions II Method variables 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 nonmeaningful names for class or instance variables Rule 28 Use standard names for throwaway variables 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 Rule 12 Join the vowel generation Despite the cutesy name this rule is important In more primitive languages names were often limited to 8 or so characters This led to names like maxVolum and lngPlyng The usual rule was to leave out vowels starting from the right Such names are harder to read and to remember Do not leave out vowels or otherwise use unusual abbreviations in Java Naming classes Rule 18 Capitalize the first letter of each word including the first PrintStream Person ExemptEmployee Rule 19 Use nouns to name classes ExemptEmployee CustomerAccount Classes are supposed to represent things Naming variables Rule 25 Capitalize the first letter of each word except the first total maxValue Rule 26 Use nouns to name variables balance outputLine Variables are supposed to represent values Naming methods Rule 22 Capitalize the first letter of each word except the first display displayImage Methods are capitalized the same as variables Rule 23 Use verbs when naming methods displayImage computeBalance Methods are supposed to do something Rule 13 Capitalize only the first letter in acronyms In names write acronyms such as GUI and API as Gui and Api Examples setDstOffset displayAsHtml loadXmlDocument Since capital letters are used to separate names this rule helps avoid confusion 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 Rule 31 Constants are written in ALL CAPITALS with underscores between words Exception color names such as Color pink Colors were defined before conventions were established Will you be held responsible for following these rules Yes The End
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