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AnkiDroid_code_conventions.html
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AnkiDroid_code_conventions.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html>
<head>
<title>AnkiDroid Code Conventions</title>
<meta name="Author" content="AnkiDroid">
<meta name="Keywords" content="java, programming, code, style, guideline, guidelines, recommendation, recommendations, layout, standard, conventions, standardization, naming, names, indentation, block, readability, maintainability, mixed case, suffix, prefix, statement, statements, conditional, white space, align, alignment comments, javadoc, code complete, steve mcconnel, software, services">
<meta name="Description"
content="Android Programming Style Guidelines. Coding recommensations for Android developers including naming conventions, code layout, commenting and more.">
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<link rel=stylesheet href="style.css" type="text/css">
</head>
<body>
<table cellpadding=10 border=0 cellspacing=0>
<tr>
<p>
<!--
*******************************************************************************
HEADING
*******************************************************************************
-->
<table width="100%">
<tr>
<td width="90%">
<center>
<h1>AnkiDroid Code Conventions</h1>
<em> Version 1.0, September 2010 </em><br>
<em> AnkiDroid </em><br>
<em> Copyright © 2010</em><br>
<p>
This document is available for download at <a href="http://code.google.com/p/ankidroid/downloads/list">http://code.google.com/p/ankidroid/downloads/list</a>
<a href=""></a>
</center>
</td>
<td width="10%">
<img src="anki.png" alt="AnkiDroid" align="right" vspace=10 hspace=30>
</td>
</tr>
</table>
<p>
<hr width="100%">
<!--
*******************************************************************************
TABLE OF CONTENT
*******************************************************************************
-->
<h1>
Table of Content
</h1>
<ul>
<li><a href="#introduction">
1 Introduction</a>
<ul>
<li><a href="#Layout of the Recommendations">
1.1 Layout of the Recommendations</a></li>
<li><a href="#Recommendation">
1.2 Recommendations Importance</a></li>
<li><a href="#Checkstyle and Formatter">
1.3 Automatic Style Checking and Formatting</a></li>
</ul>
</li>
<li><a href="#General Recommendations">
2 General Recommendations</a></li>
<li><a href="#Naming Conventions">
3 Naming Conventions</a>
<ul>
<li><a href="#General">
3.1 General Naming Conventions</a></li>
<li><a href="#Specific">
3.2 Specific Naming Conventions</a></li>
</ul>
</li>
<li><a href="#Layout Techniques">
4 Layout Techniques</a>
<ul>
<li><a href="#Length Line">
4.1 Length Line</a></li>
<li><a href="#Indentation">
4.2 Indentation</a></li>
<li><a href="#Braces">
4.3 Braces</a></li>
<li><a href="#White Spaces">
4.4 White Spaces</a></li>
<li><a href="#Blank Lines">
4.5 Blank Lines</a></li>
</ul>
</li>
<li><a href="#Control Structures">
5 Control Structures</a>
<ul>
<li><a href="#if">
5.1 if</a></li>
<li><a href="#for">
5.2 for</a></li>
<li><a href="#while">
5.3 while</a></li>
<li><a href="#do-while">
5.4 do-while</a></li>
<li><a href="#switch">
5.5 switch</a></li>
<li><a href="#try-catch">
5.6 try-catch</a></li>
</ul>
</li>
<li><a href="#Comments">
6 Comments</a></li>
<li><a href="#Logging">
7 Logging</a></li>
<li><a href="#File Organization">
8 File Organization</a></li>
<li><a href="#Miscellaneous">
9 Miscellaneous</a></li>
<ul>
<li><a href="#general">
9.1 General</a></li>
<li><a href="#types">
9.2 Types</a></li>
<li><a href="#variables and constants">
9.3 Variables and Constants</a></li>
<li><a href="#operators">
9.4 Operators</a></li>
<li><a href="#conditionals">
9.5 Conditionals</a></li>
<li><a href="#loops">
9.6 Loops</a></li>
<li><a href="#exceptions and finalizers">
9.7 Exceptions and Finalizers</a></li>
<li><a href="#android xml layouts">
9.8 Android XML Layouts</a></li>
</ul>
<li><a href="#Cheat Sheet">
10 Cheat Sheet</a></li>
<li><a href="#References">
11 References</a></li>
</ul>
<hr width="100%">
<!--
*******************************************************************************
1 INTRODUCTION
*******************************************************************************
-->
<h1>
<a name="introduction"></a>1 Introduction
</h1>
This document lists the recommendations applied to AnkiDroid, an Android project based on Anki.
<p>
<!--
The recommendations are based on individual experience and on the next coding standards:
<a href="#ref1">[1]</a>,
<a href="#ref2">[2]</a>,
<a href="#ref3">[3]</a>,
<a href="#ref4">[4]</a>,
<a href="#ref5">[5]</a> and
<a href="#ref6">[6]</a>.
<br/><br/>
-->
If you find any error on this document or any inconsistency between the recommendations presented here and the automatic checkstyle and formatter, please send an email to <a href="mailto:ankidroid@gmail.com">ankidroid@gmail.com</a>.
<h3>
<a name="Layout of the Recommendations"></a>1.1 Layout of the Recommendations
</h3>
<p>
Layout for the recommendations is as follows:
<p>
<table class="rule" width="100%">
<tr>
<td class="recom">
n. Guideline short description
</td>
</tr>
<tr>
<td class="example">Example if applicable
</td>
</tr>
<!--
<tr>
<td class="rationale">
Motivation, background and additional information.
</td>
</tr>
-->
</table>
<h3>
<a name="Recommendation"></a>1.2 Recommendations Importance
</h3>
In this document the words <em>must</em>, <em>should</em> and <em>can</em> are used to convey the importance of a recommendation. A <em>must</em> requeriment have to be followed, a <em>should</em> is a strong recommendation and a <em>can</em> is a general suggestion.
<h3>
<a name="Checkstyle and Formatter"></a>1.3 Automatic Style Checking and Formatting
</h3>
In order to benefit from automatic code style checking, following the recommendations below, install the <em>Checkstyle</em> plugin in your IDE and use this configuration file: <a href="http://ankidroid.googlecode.com/files/ankidroid.checkstyle.xml">ankidroid.checkstyle.xml</a>
<br/><br/>
In Eclipse, if you would like to format automatically the code, download the configuration files for <em>Clean Up</em>, <em>Formatter</em> and <em>Organize Imports</em> and import them to Eclipse. These files can be found here: <a href="http://ankidroid.googlecode.com/files/AnkiDroid%20Formatter%2C%20Clean%20Up%20and%20Import%20Order.zip">AnkiDroid Formatter, Clean Up and Import Order.zip</a>
<!--
*******************************************************************************
GENERAL RECOMMENDATIONS
*******************************************************************************
-->
<p>
<h1>
<a name="General Recommendations"></a>2 General Recommendations
</h1>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
1. Any violation to the guide is allowed if it enhances one of the following, by order of importance (higher levels cannot be sacrificed for lower levels):
</td>
</tr>
<tr>
<td class="example">- Logical Structure
- Consistency
- Readability
- Ease of modifications
</td>
</tr>
</table>
<!--
*******************************************************************************
NAMING CONVENSIONS
*******************************************************************************
-->
<p>
<h1>
<a name="Naming Conventions"></a>3 Naming Conventions
</h1>
<h3>
<a name="General"></a>3.1 General Naming Conventions
</h3>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%">
<tr>
<td class="recom">
2. All names should be written in English.
</td>
</tr>
<tr>
<td class="example"></td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%">
<tr>
<td class="recom">
3. Package names should be in all lower case.
</td>
</tr>
<tr>
<td class="example">com.company.application.ui
com.sun.eng
edu.cmu.cs.bovik.cheese
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
4. Class names must be nouns, in mixed case with the first letter of each internal word capitalized.
</td>
</tr>
<tr>
<td class="example">class Line;
class AudioSystem;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
5. Variable names must be in mixed case starting with lower case.
</td>
</tr>
<tr>
<td class="example">int age;
float availableWidth;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
6. Non-public, non-static field names should start with m.
</td>
</tr>
<tr>
<td class="example">private long mLongVariable;
private int mIntVariable;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
7. Static field names should start with s.
</td>
</tr>
<tr>
<td class="example">private static MyClass sSingleton;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
8. Constant (final variables) names must be all uppercase using underscore to separate words.
</td>
</tr>
<tr>
<td class="example">public static final int SOME_CONSTANT = 42;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
9. Associated constants (final variables) should be prefixed by a common type name.
</td>
</tr>
<tr>
<td class="example">public static final int COLOR_RED = 1;
public static final int COLOR_GREEN = 2;
public static final int COLOR_BLUE = 3;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
10. Method names should be verbs in mixed case, with the first letter in lowercase and with the first letter of each internal word capitalized.
</td>
</tr>
<tr>
<td class="example">getName();
computeTotalWidth();
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
11. Functions (methods with a return) should be named after what they return and procedures (<em>void</em> methods) after what they do.
</td>
</tr>
<tr>
<td class="example">
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
12. In a method name, the name of the object is implicit and should be avoided.
</td>
</tr>
<tr>
<td class="example">employee.getName(); <i class="not">// NOT: employee.getEmployeeName();</i>
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
13. Negated boolean variable names must be avoided.
</td>
</tr>
<tr>
<td class="example">boolean isLoaded; <i class="not">// NOT: boolean isNotLoaded;</i>
boolean isError; <i class="not">// NOT: boolean isNotError;</i>
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
14. Abbreviations in names should be avoided.
</td>
</tr>
<tr>
<td class="example">computeAverage(); <i class="not">// NOT: compAvg();</i>
ActionEvent event; <i class="not">// NOT: ActionEvent e;</i>
catch (Exception exception) { <i class="not">// NOT: catch (Exception e) {</i>
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
15. Abbreviations and acronyms should not be uppercase when used in a name.
</td>
</tr>
<tr>
<td class="example">getCustomerId(); <i class="not">// NOT: getCustomerID();</i>
exportHtmlSource(); <i class="not">// NOT: exportHTMLSource();</i>
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
16. Generic variables should have the same name as their type.
</td>
</tr>
<tr>
<td class="example">void setView(View view); <i class="not">// NOT: void setView(View v);</i>
<i class="not">// NOT: void setView(View aView);</i>
void close(Database database); <i class="not">// NOT: void close(Database db);</i>
<i class="not">// NOT: void close(Database sqliteDB);</i>
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
17. The terms <em>get/set</em> must be used where a class attribute is accessed directly.
</td>
</tr>
<tr>
<td class="example">author.getName();
author.setName(name);
point.getX();
point.setX(3);
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
18. <em>is</em> prefix should be used for boolean variables and methods. Alternatively and if it fits better, <em>has</em>, <em>can</em> and <em>should</em> prefixes can be used.
</td>
</tr>
<tr>
<td class="example">boolean isVisible;
boolean isOpen();
boolean hasLicense();
boolean canEvaluate();
boolean shouldAbort = false;
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
19. The term <em>compute</em> can be used in methods where something is computed.
</td>
</tr>
<tr>
<td class="example">valueSet.computeAverage();
matrix.computeInverse();
</td>
</tr>
</table>
<!--
****************************************************************************
Rule
****************************************************************************
-->
<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
20. The term <em>find</em> can be used in methods where something is looked up.
</td>
</tr>
<tr>
<td class="example">vertex.findNearestVertex();
matrix.findSmallestElement();
node.findShortestPath(Node destinationNode);
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
21. The term <em>initialize</em> can be used where an object or a concept is set up.
</td>
</tr>
<tr>
<td class="example">initializeViews();
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
22. Variables with a large scope should have very descriptive (and usually long) names, variables with a small scope can have short names.
</td>
</tr>
<tr>
<td class="example">
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
23. Iterator variables can be called i, j, k, m, n...
</td>
</tr>
<tr>
<td class="example">for (int i = 0; i < downloads.size(); i++) {
statements;
}
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
24. Plural form should be used on names representing a collection of objects.
</td>
</tr>
<tr>
<td class="example">ArrayList<Download> downloads;
int[] points;
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
25. <em>num</em> prefix should be used for variables representing a number of objects.
</td>
</tr>
<tr>
<td class="example">int numPoints = points.length();
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
26. <em>Number</em> suffix should be used for variables representing an entity number.
</td>
</tr>
<tr>
<td class="example">int employeeNumber;
int comicNumber;
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
27. Exception classes should have <em>Exception</em> like a suffix.
</td>
</tr>
<tr>
<td class="example">class CustomException extends Exception {
...
}
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
28. Singleton classes should return their unique instance through the <em>getInstance</em> method.
</td>
</tr>
<tr>
<td class="example">class MySingletonClass {
private final static MySingletonClass sInstance = new MySingletonClass();
private MySingletonClass() {
...
}
public static MySingletonClass getInstance() { <i class="not">// NOT: get() or instance()...</i>
return sInstance;
}
}
</td>
</tr>
</table>
<h3>
<a name="Specific"></a>3.1 Specific Naming Conventions
</h3>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
29. String key resources must be all lowercase using underscore to separate words.
</td>
</tr>
<tr>
<td class="example"><string name="good_example_key">Example value</string> <i class="not">// NOT: <string name="badExampleKey">Example value</string></i>
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
30. XML elements identifiers must be all lowercase using underscore to separate words.
</td>
</tr>
<tr>
<td class="example"><TextView android:id="@+id/good_id_example" <i class="not">// NOT: <TextView android:id="@+id/badIdExample"</i>
android:layout_width="wrap_content" <i class="not">android:layout_width="wrap_content"</i>
android:layout_height="wrap_content" <i class="not">android:layout_height="wrap_content"</i>
/> <i class="not">/></i>
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
31. Activiy names can have <em>Activity</em> like a suffix.
</td>
</tr>
<tr>
<td class="example">public class ExampleActivity extends Activity {
...
}
</td>
</tr>
</table>
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<p>
<table class="rule" width="100%" >
<tr>
<td class="recom">
32. Test method names should be composed by a name representing what is being tested and a name stating which specific case is being tested, separated with underscore.
</td>
</tr>