Beginning StyleBe consistent!Do it right the first timeIndent nested codeBreak up long linesDon’t use “hard” tabsUsing spacesUse meaningful namesMeaningful names: exceptions IMeaningful names: exceptions IIMeaningful names: exceptions IIINaming classes and interfacesNaming variablesNaming constantsNaming methodsKeep your methods shortCorrect style made easyThe EndJan 14, 2019Beginning Style2Be consistent!Most times, you will enter an ongoing project, with established style rulesFollow them even if you don’t like themIn this course you will be working in teams with various other peopleWe’ll all use the same set of style rules3Do it right the first timeYou only write code once, but you read it many times while you’re trying to get it to workGood 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 quicklyGuess which program will be around longer and used by more people?4Indent nested codeAlways indent statements that are nested inside (under the control of) another statementif (itemCost <= bankBalance) { writeCheck(itemCost); bankBalance = bankBalance - itemCost;}The open brace always goes at the end of a lineThe matching close brace lines up with the statement being closedIndentation should be consistent throughout the programFor Java, 4 spaces is the standard5Break up long linesKeep your lines short enough to be viewed and printedMany people use 72 or 80 character limitsSuggestions on where to break a long line:It’s illegal to break a line within a quoted stringBreak after, not before, operatorsLine up parameters to a methodDon’t indent the second line of a control statement with a long test so that it lines up with the statements being controlled6Don’t use “hard” tabsA hard tab is an actual tab character in your textIt tells the program to go to the next tab stop (wherever that is)Not every program puts tab stops in the same placeIf you use hard tabs to indent, sooner or later your nice indentation will be ruinedGood 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 charactersWith soft tabs, your indentation is always safeThe default Eclipse indentation, with mixed tabs and spaces, is wrong7Using spacesUse 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 thisUse 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);8Use meaningful namesNames should be chosen very carefully, to indicate the purpose of a variable or methodIf the purpose changes, the name should be changedSpend a little time to choose the best name for each of your variables and methods!Long, multiword names are common in JavaHowever, if a name is too long, maybe you’re trying to use it for too many purposesDon’t change the name, separate the purposesDon’t abbreviate namesLet Eclipse help you—start typing the name, then hit control-spaceVery common abbreviations, such as max for “maximum”, are OK9Meaningful names: exceptions IIt 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 third-level loopThis is almost always better than trying to come up with a meaningful nameExample:for (int i = 1; i <= 10; i++) { for (int j = 1, j <= 10; j++) { System.out.println(" " + (i * j)); }}10Meaningful names: exceptions IILocal variables in methods may be given short, simple names, if:The purpose of the variable is obvious from context, andThe variable is used only briefly, in a small part of the programBut never use meaningless names for fields (class or instance variables) or classes or methods11Meaningful names: exceptions IIIIf variables have no special meaning, you can use names that reflect their typesFor 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 namess, t, u, or s1, s2, etc. are often used for Stringsp, q, r, s are often used for booleansw, x, y, z are often used for real numbers12Naming classes and interfacesCapitalize the first letter of each word, including the first word: PrintStream, Person, ExemptEmployeeUse nouns to name classes: ExemptEmployee, CustomerAccountClasses are supposed to represent thingsUse adjectives to name interfaces: Comparable, PrintableInterfaces are supposed to represent features13Naming variablesCapitalize the first letter of each word except the first: total, maxValueUse nouns to name variables: balance, outputLineVariables are supposed to represent values14Naming constantsA constant is an identifier whose value, once given, cannot be changedConstants 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 words15Naming methodsCapitalize the first letter of each word except the first: display, displayImageMethods are capitalized the same as variablesUse verbs when naming methods: displayImage, computeBalanceMethods are supposed to do something16Keep your methods shortMethods give you a chance to nam e what you are doingWell-chosen names can greatly improve readabilityIf your method does A, then B, then C, it will probably improve readability to make A, B, and C into methodsEclipse makes it easy to refactor a long methodRefactoring is changing the structure of a program, without changing in any way what the program doesIn Eclipse,Choose a range of linesChoose Refactor -> Extract MethodGive your new method a name, and Eclipse does the restThis refactoring is possible if (and only if) the resultant method needs to return only a single value17Correct style made easyIn Eclipse,Go to Window Preferences Java Code
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