Docs: Fixing typo, general edits, updating page title in toc
Bug: 26010281
Change-Id: I053373b5374a2e28bc782013144fc34b1148fa63
diff --git a/src/source/code-style.jd b/src/source/code-style.jd
index dd52b5d..364b0e9 100644
--- a/src/source/code-style.jd
+++ b/src/source/code-style.jd
@@ -1,8 +1,8 @@
-page.title=Code Style Guidelines for Contributors
+page.title=Code Style for Contributors
@jd:body
<!--
- Copyright 2013 The Android Open Source Project
+ Copyright 2015 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
@@ -24,43 +24,42 @@
</div>
</div>
-<p>The rules below are not guidelines or recommendations, but strict rules.
-Contributions to Android generally <em>will not be accepted</em> if they do not
-adhere to these rules.</p>
-
-<p>Not all existing code follows these rules, but all new code is expected to.</p>
+<p>The code styles below are strict rules, not guidelines or recommendations.
+Contributions to Android that do not adhere to these rules are generally <em>not
+accepted</em>. We recognize that not all existing code follows these rules, but
+we expect all new code to be compliant.</p>
<h2 id="java-language-rules">Java Language Rules</h2>
-<p>We follow standard Java coding conventions. We add a few rules:</p>
+<p>Android follows standard Java coding conventions with the additional rules
+described below.</p>
+
<h3 id="dont-ignore-exceptions">Don't Ignore Exceptions</h3>
-<p>Sometimes it is tempting to write code that completely ignores an exception
-like this:</p>
+<p>It can be tempting to write code that completely ignores an exception, such
+as:</p>
<pre><code>void setServerPort(String value) {
try {
serverPort = Integer.parseInt(value);
} catch (NumberFormatException e) { }
}
</code></pre>
-<p>You must never do this. While you may think that your code will never
-encounter this error condition or that it is not important to handle it,
-ignoring exceptions like above creates mines in your code for someone else to
-trip over some day. You must handle every Exception in your code in some
-principled way. The specific handling varies depending on the case.</p>
+<p>Do not do this. While you may think your code will never encounter this error
+condition or that it is not important to handle it, ignoring exceptions as above
+creates mines in your code for someone else to trigger some day. You must handle
+every Exception in your code in a principled way; the specific handling varies
+depending on the case.</p>
<p><em>Anytime somebody has an empty catch clause they should have a
creepy feeling. There are definitely times when it is actually the correct
thing to do, but at least you have to think about it. In Java you can't escape
the creepy feeling.</em> -<a href="http://www.artima.com/intv/solid4.html">James Gosling</a></p>
<p>Acceptable alternatives (in order of preference) are:</p>
<ul>
-<li>
-<p>Throw the exception up to the caller of your method.</p>
+<li>Throw the exception up to the caller of your method.
<pre><code>void setServerPort(String value) throws NumberFormatException {
serverPort = Integer.parseInt(value);
}
</code></pre>
</li>
-<li>
-<p>Throw a new exception that's appropriate to your level of abstraction.</p>
+<li>Throw a new exception that's appropriate to your level of abstraction.
<pre><code>void setServerPort(String value) throws ConfigurationException {
try {
serverPort = Integer.parseInt(value);
@@ -70,24 +69,22 @@
}
</code></pre>
</li>
-<li>
-<p>Handle the error gracefully and substitute an appropriate value in the
-catch {} block.</p>
+<li>Handle the error gracefully and substitute an appropriate value in the
+catch {} block.
<pre><code>/** Set port. If value is not a valid number, 80 is substituted. */
void setServerPort(String value) {
try {
serverPort = Integer.parseInt(value);
} catch (NumberFormatException e) {
- serverPort = 80; // default port for server
+ serverPort = 80; // default port for server
}
}
</code></pre>
</li>
-<li>
-<p>Catch the Exception and throw a new <code>RuntimeException</code>. This is dangerous:
-only do it if you are positive that if this error occurs, the appropriate
-thing to do is crash.</p>
+<li>Catch the Exception and throw a new <code>RuntimeException</code>. This is
+dangerous, so do it only if you are positive that if this error occurs the
+appropriate thing to do is crash.
<pre><code>/** Set port. If value is not a valid number, die. */
void setServerPort(String value) {
@@ -98,14 +95,13 @@
}
}
</code></pre>
-<p>Note that the original exception is passed to the constructor for
-RuntimeException. If your code must compile under Java 1.3, you will need to
-omit the exception that is the cause.</p>
+<p class="note"><strong>Note</strong> The original exception is passed to the
+constructor for RuntimeException. If your code must compile under Java 1.3, you
+must omit the exception that is the cause.</p>
</li>
-<li>
-<p>Last resort: if you are confident that actually ignoring the exception is
+<li>As a last resort, if you are confident that ignoring the exception is
appropriate then you may ignore it, but you must also comment why with a good
-reason:</p>
+reason:
<pre><code>/** If value is not a valid number, original port number is used. */
void setServerPort(String value) {
try {
@@ -118,33 +114,33 @@
</code></pre>
</li>
</ul>
+
<h3 id="dont-catch-generic-exception">Don't Catch Generic Exception</h3>
-<p>Sometimes it is tempting to be lazy when catching exceptions and do
+<p>It can also be tempting to be lazy when catching exceptions and do
something like this:</p>
<pre><code>try {
- someComplicatedIOFunction(); // may throw IOException
- someComplicatedParsingFunction(); // may throw ParsingException
- someComplicatedSecurityFunction(); // may throw SecurityException
- // phew, made it all the way
-} catch (Exception e) { // I'll just catch all exceptions
+ someComplicatedIOFunction(); // may throw IOException
+ someComplicatedParsingFunction(); // may throw ParsingException
+ someComplicatedSecurityFunction(); // may throw SecurityException
+ // phew, made it all the way
+} catch (Exception e) { // I'll just catch all exceptions
handleError(); // with one generic handler!
}
</code></pre>
-<p>You should not do this. In almost all cases it is inappropriate to catch
-generic Exception or Throwable, preferably not Throwable, because it includes
-Error exceptions as well. It is very dangerous. It means that Exceptions you
-never expected (including RuntimeExceptions like ClassCastException) end up
-getting caught in application-level error handling. It obscures the failure
-handling properties of your code. It means if someone adds a new type of
-Exception in the code you're calling, the compiler won't help you realize you
-need to handle that error differently. And in most cases you shouldn't be
-handling different types of exception the same way, anyway.</p>
-<p>There are rare exceptions to this rule: certain test code and top-level
-code where you want to catch all kinds of errors (to prevent them from showing
-up in a UI, or to keep a batch job running). In that case you may catch
-generic Exception (or Throwable) and handle the error appropriately. You
-should think very carefully before doing this, though, and put in comments
-explaining why it is safe in this place.</p>
+<p>Do not do this. In almost all cases it is inappropriate to catch generic
+Exception or Throwable (preferably not Throwable because it includes Error
+exceptions). It is very dangerous because it means that Exceptions
+you never expected (including RuntimeExceptions like ClassCastException) get
+caught in application-level error handling. It obscures the failure handling
+properties of your code, meaning if someone adds a new type of Exception in the
+code you're calling, the compiler won't help you realize you need to handle the
+error differently. In most cases you shouldn't be handling different types of
+exception the same way.</p>
+<p>The rare exception to this rule is test code and top-level code where you
+want to catch all kinds of errors (to prevent them from showing up in a UI, or
+to keep a batch job running). In these cases you may catch generic Exception
+(or Throwable) and handle the error appropriately. Think very carefully before
+doing this, though, and put in comments explaining why it is safe in this place.</p>
<p>Alternatives to catching generic Exception:</p>
<ul>
<li>
@@ -166,59 +162,58 @@
not catching an exception, don't scowl. Smile: the compiler just made it
easier for you to catch runtime problems in your code.</p>
<h3 id="dont-use-finalizers">Don't Use Finalizers</h3>
-<p>Finalizers are a way to have a chunk of code executed
-when an object is garbage collected.</p>
-<p>Pros: can be handy for doing cleanup, particularly of external resources.</p>
-<p>Cons: there are no guarantees as to when a finalizer will be called,
-or even that it will be called at all.</p>
-<p>Decision: we don't use finalizers. In most cases, you can do what
+<p>Finalizers are a way to have a chunk of code executed when an object is
+garbage collected. While they can be handy for doing cleanup (particularly of
+external resources, there are no guarantees as to when a finalizer will be
+called (or even that it will be called at all).</p>
+<p>Android doesn't use finalizers. In most cases, you can do what
you need from a finalizer with good exception handling. If you absolutely need
it, define a close() method (or the like) and document exactly when that
-method needs to be called. See InputStream for an example. In this case it is
+method needs to be called (see InputStream for an example). In this case it is
appropriate but not required to print a short log message from the finalizer,
as long as it is not expected to flood the logs.</p>
+
<h3 id="fully-qualify-imports">Fully Qualify Imports</h3>
<p>When you want to use class Bar from package foo,there
are two possible ways to import it:</p>
-<ol>
-<li><code>import foo.*;</code></li>
-</ol>
-<p>Pros: Potentially reduces the number of import statements.</p>
-<ol>
-<li><code>import foo.Bar;</code></li>
-</ol>
-<p>Pros: Makes it obvious what classes are actually used. Makes
-code more readable for maintainers. </p>
-<p>Decision: Use the latter for importing all Android code. An explicit
-exception is made for java standard libraries (<code>java.util.*</code>, <code>java.io.*</code>, etc.)
-and unit test code (<code>junit.framework.*</code>)</p>
+<ul>
+<li><code>import foo.*;</code>
+<p>Potentially reduces the number of import statements.</p></li>
+<li><code>import foo.Bar;</code>
+<p>Makes it obvious what classes are actually used and the code is more readable
+for maintainers.</p></li></ul>
+<p>Use <code>import foo.Bar;</code> for importing all Android code. An explicit
+exception is made for java standard libraries (<code>java.util.*</code>,
+<code>java.io.*</code>, etc.) and unit test code
+(<code>junit.framework.*</code>).</p>
+
<h2 id="java-library-rules">Java Library Rules</h2>
<p>There are conventions for using Android's Java libraries and tools. In some
cases, the convention has changed in important ways and older code might use a
deprecated pattern or library. When working with such code, it's okay to
-continue the existing style. When creating new components never use deprecated
-libraries.</p>
+continue the existing style. When creating new components however, never use
+deprecated libraries.</p>
<h2 id="java-style-rules">Java Style Rules</h2>
<h3 id="use-javadoc-standard-comments">Use Javadoc Standard Comments</h3>
-<p>Every file should have a copyright statement at the top. Then a package
-statement and import statements should follow, each block separated by a blank
-line. And then there is the class or interface declaration. In the Javadoc
-comments, describe what the class or interface does.</p>
+<p>Every file should have a copyright statement at the top, followed by package
+and import statements (each block separated by a blank line) and finally the
+class or interface declaration. In the Javadoc comments, describe what the class
+or interface does.</p>
<pre><code>/*
- * Copyright (C) 2013 The Android Open Source Project
+ * Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
+ * You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
- * Unless required by applicable law or agreed to in writing, software
+ * Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
+ * See the License for the specific language governing permissions and
* limitations under the License.
*/
@@ -240,7 +235,7 @@
</code></pre>
<p>Every class and nontrivial public method you write <em>must</em> contain a
Javadoc comment with at least one sentence describing what the class or method
-does. This sentence should start with a 3rd person descriptive verb.</p>
+does. This sentence should start with a third person descriptive verb.</p>
<p>Examples:</p>
<pre><code>/** Returns the correctly rounded positive square root of a double value. */
static double sqrt(double a) {
@@ -249,7 +244,7 @@
</code></pre>
<p>or</p>
<pre><code>/**
- * Constructs a new String by converting the specified array of
+ * Constructs a new String by converting the specified array of
* bytes using the platform's default character encoding.
*/
public String(byte[] bytes) {
@@ -257,40 +252,42 @@
}
</code></pre>
<p>You do not need to write Javadoc for trivial get and set methods such as
-<code>setFoo()</code> if all your Javadoc would say is "sets Foo". If the method does
-something more complex (such as enforcing a constraint or having an important
-side effect), then you must document it. And if it's not obvious what the
-property "Foo" means, you should document it.</p>
-<p>Every method you write, whether public or otherwise, would benefit from
-Javadoc. Public methods are part of an API and therefore require Javadoc.</p>
-<p>Android does not currently enforce a specific style for writing Javadoc
-comments, but you should follow the instructions <a
+<code>setFoo()</code> if all your Javadoc would say is "sets Foo". If the method
+does something more complex (such as enforcing a constraint or has an important
+side effect), then you must document it. If it's not obvious what the property
+"Foo" means, you should document it.
+<p>Every method you write, public or otherwise, would benefit from Javadoc.
+Public methods are part of an API and therefore require Javadoc. Android does
+not currently enforce a specific style for writing Javadoc comments, but you
+should follow the instructions <a
href="http://www.oracle.com/technetwork/java/javase/documentation/index-137868.html">How
to Write Doc Comments for the Javadoc Tool</a>.</p>
<h3 id="write-short-methods">Write Short Methods</h3>
-<p>To the extent that it is feasible, methods should be kept small and
-focused. It is, however, recognized that long methods are sometimes
-appropriate, so no hard limit is placed on method length. If a method exceeds
-40 lines or so, think about whether it can be broken up without harming the
-structure of the program.</p>
+<p>When feasible, keep methods small and focused. We recognize that long methods
+are sometimes appropriate, so no hard limit is placed on method length. If a
+method exceeds 40 lines or so, think about whether it can be broken up without
+harming the structure of the program.</p>
+
<h3 id="define-fields-in-standard-places">Define Fields in Standard Places</h3>
-<p>Fields should be defined either at the top of the file, or immediately before the methods that use them.</p>
+<p>Define fields either at the top of the file or immediately before the
+methods that use them.</p>
+
<h3 id="limit-variable-scope">Limit Variable Scope</h3>
-<p>The scope of local variables should be kept to a minimum. By doing so, you increase the readability and
-maintainability of your code and reduce the likelihood of error. Each variable
-should be declared in the innermost block that encloses all uses of the
-variable.</p>
+<p>Keep the scope of local variables to a minimum. By doing so, you
+increase the readability and maintainability of your code and reduce the
+likelihood of error. Each variable should be declared in the innermost block
+that encloses all uses of the variable.</p>
<p>Local variables should be declared at the point they are first used. Nearly
every local variable declaration should contain an initializer. If you don't
-yet have enough information to initialize a variable sensibly, you should
-postpone the declaration until you do.</p>
-<p>One exception to this rule concerns try-catch statements. If a variable is
-initialized with the return value of a method that throws a checked exception,
-it must be initialized inside a try block. If the value must be used outside
-of the try block, then it must be declared before the try block, where it
-cannot yet be sensibly initialized:</p>
-<pre><code>// Instantiate class cl, which represents some sort of Set
+yet have enough information to initialize a variable sensibly, postpone the
+declaration until you do.</p>
+<p>The exception is try-catch statements. If a variable is initialized with the
+return value of a method that throws a checked exception, it must be initialized
+inside a try block. If the value must be used outside of the try block, then it
+must be declared before the try block, where it cannot yet be sensibly
+initialized:</p>
+<pre><code>// Instantiate class cl, which represents some sort of Set
Set s = null;
try {
s = (Set) cl.newInstance();
@@ -300,12 +297,13 @@
throw new IllegalArgumentException(cl + " not instantiable");
}
-// Exercise the set
+// Exercise the set
s.addAll(Arrays.asList(args));
</code></pre>
-<p>But even this case can be avoided by encapsulating the try-catch block in a method:</p>
+<p>However, even this case can be avoided by encapsulating the try-catch block
+in a method:</p>
<pre><code>Set createSet(Class cl) {
- // Instantiate class cl, which represents some sort of Set
+ // Instantiate class cl, which represents some sort of Set
try {
return (Set) cl.newInstance();
} catch(IllegalAccessException e) {
@@ -317,7 +315,7 @@
...
-// Exercise the set
+// Exercise the set
Set s = createSet(cl);
s.addAll(Arrays.asList(args));
</code></pre>
@@ -332,6 +330,7 @@
doSomethingElse(i.next());
}
</code></pre>
+
<h3 id="order-import-statements">Order Import Statements</h3>
<p>The ordering of import statements is:</p>
<ol>
@@ -339,7 +338,8 @@
<p>Android imports</p>
</li>
<li>
-<p>Imports from third parties (<code>com</code>, <code>junit</code>, <code>net</code>, <code>org</code>)</p>
+<p>Imports from third parties (<code>com</code>, <code>junit</code>,
+<code>net</code>, <code>org</code>)</p>
</li>
<li>
<p><code>java</code> and <code>javax</code></p>
@@ -348,47 +348,51 @@
<p>To exactly match the IDE settings, the imports should be:</p>
<ul>
<li>
-<p>Alphabetical within each grouping, with capital letters before lower case letters (e.g. Z before a).</p>
+<p>Alphabetical within each grouping, with capital letters before lower case
+letters (e.g. Z before a).</p>
</li>
<li>
-<p>There should be a blank line between each major grouping (<code>android</code>, <code>com</code>, <code>junit</code>, <code>net</code>, <code>org</code>, <code>java</code>, <code>javax</code>).</p>
+<p>Separated by a blank line between each major grouping (<code>android</code>,
+<code>com</code>, <code>junit</code>, <code>net</code>, <code>org</code>,
+<code>java</code>, <code>javax</code>).</p>
</li>
</ul>
-<p>Originally there was no style requirement on the ordering. This meant that
-the IDE's were either always changing the ordering, or IDE developers had to
-disable the automatic import management features and maintain the imports by
-hand. This was deemed bad. When java-style was asked, the preferred styles
-were all over the map. It pretty much came down to our needing to "pick an
-ordering and be consistent." So we chose a style, updated the style guide, and
-made the IDEs obey it. We expect that as IDE users work on the code, the
-imports in all of the packages will end up matching this pattern without any
-extra engineering effort.</p>
+<p>Originally, there was no style requirement on the ordering, meaning IDEs were
+either always changing the ordering or IDE developers had to disable the
+automatic import management features and manually maintain the imports. This was
+deemed bad. When java-style was asked, the preferred styles varied wildly and it
+came down to Android needing to simply "pick an ordering and be consistent." So
+we chose a style, updated the style guide, and made the IDEs obey it. We expect
+that as IDE users work on the code, imports in all packages will match this
+pattern without extra engineering effort.</p>
<p>This style was chosen such that:</p>
<ul>
<li>
-<p>The imports people want to look at first tend to be at the top (<code>android</code>)</p>
+<p>The imports people want to look at first tend to be at the top
+(<code>android</code>).</p>
</li>
<li>
-<p>The imports people want to look at least tend to be at the bottom (<code>java</code>)</p>
+<p>The imports people want to look at least tend to be at the bottom
+(<code>java</code>).</p>
</li>
<li>
-<p>Humans can easily follow the style</p>
+<p>Humans can easily follow the style.</p>
</li>
<li>
-<p>IDEs can follow the style</p>
+<p>IDEs can follow the style.</p>
</li>
</ul>
<p>The use and location of static imports have been mildly controversial
-issues. Some people would prefer static imports to be interspersed with the
-remaining imports, some would prefer them reside above or below all other
-imports. Additionally, we have not yet come up with a way to make all IDEs use
-the same ordering.</p>
-<p>Since most people consider this a low priority issue, just use your
-judgement and please be consistent.</p>
+issues. Some people prefer static imports to be interspersed with the
+remaining imports, while some prefer them to reside above or below all
+other imports. Additionally, we have not yet determined how to make all IDEs use
+the same ordering. Since many consider this a low priority issue, just use your
+judgement and be consistent.</p>
+
<h3 id="use-spaces-for-indentation">Use Spaces for Indentation</h3>
-<p>We use 4 space indents for blocks. We never use tabs. When in doubt, be
-consistent with code around you.</p>
-<p>We use 8 space indents for line wraps, including function calls and
+<p>We use four (4) space indents for blocks and never tabs. When in doubt, be
+consistent with the surrounding code.</p>
+<p>We use eight (8) space indents for line wraps, including function calls and
assignments. For example, this is correct:</p>
<pre><code>Instrument i =
someLongExpression(that, wouldNotFit, on, one, line);
@@ -397,6 +401,7 @@
<pre><code>Instrument i =
someLongExpression(that, wouldNotFit, on, one, line);
</code></pre>
+
<h3 id="follow-field-naming-conventions">Follow Field Naming Conventions</h3>
<ul>
<li>
@@ -424,7 +429,7 @@
</code></pre>
<h3 id="use-standard-brace-style">Use Standard Brace Style</h3>
<p>Braces do not go on their own line; they go on the same line as the code
-before them. So:</p>
+before them:</p>
<pre><code>class MyClass {
int func() {
if (something) {
@@ -437,63 +442,63 @@
}
}
</code></pre>
-<p>We require braces around the statements for a conditional. Except, if the
+<p>We require braces around the statements for a conditional. Exception: If the
entire conditional (the condition and the body) fit on one line, you may (but
-are not obligated to) put it all on one line. That is, this is legal:</p>
+are not obligated to) put it all on one line. For example, this is acceptable:</p>
<pre><code>if (condition) {
- body();
+ body();
}
</code></pre>
-<p>and this is legal:</p>
+<p>and this is acceptable:</p>
<pre><code>if (condition) body();
</code></pre>
-<p>but this is still illegal:</p>
+<p>but this is not acceptable:</p>
<pre><code>if (condition)
body(); // bad!
</code></pre>
+
<h3 id="limit-line-length">Limit Line Length</h3>
-<p>Each line of text in your code should be at most 100 characters long.</p>
-<p>There has been lots of discussion about this rule and the decision remains
-that 100 characters is the maximum.</p>
-<p>Exception: if a comment line contains an example command or a literal URL
+<p>Each line of text in your code should be at most 100 characters long. While
+much discussion has surrounded this rule, the decision remains that 100
+characters is the maximum <em>with the following exceptions</em>:</p>
+<ul>
+<li>If a comment line contains an example command or a literal URL
longer than 100 characters, that line may be longer than 100 characters for
-ease of cut and paste.</p>
-<p>Exception: import lines can go over the limit because humans rarely see
-them. This also simplifies tool writing.</p>
+ease of cut and paste.</li>
+<li>Import lines can go over the limit because humans rarely see them (this also
+simplifies tool writing).</li>
+</ul>
+
<h3 id="use-standard-java-annotations">Use Standard Java Annotations</h3>
<p>Annotations should precede other modifiers for the same language element.
Simple marker annotations (e.g. @Override) can be listed on the same line with
the language element. If there are multiple annotations, or parameterized
annotations, they should each be listed one-per-line in alphabetical
-order.<</p>
+order.</p>
<p>Android standard practices for the three predefined annotations in Java are:</p>
<ul>
-<li>
-<p><code>@Deprecated</code>: The @Deprecated annotation must be used whenever the use of the annotated
-element is discouraged. If you use the @Deprecated annotation, you must also
-have a @deprecated Javadoc tag and it should name an alternate implementation.
-In addition, remember that a @Deprecated method is <em>still supposed to
-work.</em></p>
-<p>If you see old code that has a @deprecated Javadoc tag, please add the @Deprecated annotation.</p>
+<li><code>@Deprecated</code>: The @Deprecated annotation must be used whenever
+the use of the annotated element is discouraged. If you use the @Deprecated
+annotation, you must also have a @deprecated Javadoc tag and it should name an
+alternate implementation. In addition, remember that a @Deprecated method is
+<em>still supposed to work</em>. If you see old code that has a @deprecated
+Javadoc tag, please add the @Deprecated annotation.
</li>
-<li>
-<p><code>@Override</code>: The @Override annotation must be used whenever a method overrides the
-declaration or implementation from a super-class.</p>
-<p>For example, if you use the @inheritdocs Javadoc tag, and derive from a
-class (not an interface), you must also annotate that the method @Overrides
-the parent class's method.</p>
-</li>
-<li>
-<p><code>@SuppressWarnings</code>: The @SuppressWarnings annotation should only be used under circumstances
-where it is impossible to eliminate a warning. If a warning passes this
-"impossible to eliminate" test, the @SuppressWarnings annotation <em>must</em> be
-used, so as to ensure that all warnings reflect actual problems in the
-code.</p>
+<li><code>@Override</code>: The @Override annotation must be used whenever a
+method overrides the declaration or implementation from a super-class. For
+example, if you use the @inheritdocs Javadoc tag, and derive from a class (not
+an interface), you must also annotate that the method @Overrides the parent
+class's method.</li>
+<li><code>@SuppressWarnings</code>: The @SuppressWarnings annotation should be
+used only under circumstances where it is impossible to eliminate a warning. If
+a warning passes this "impossible to eliminate" test, the @SuppressWarnings
+annotation <em>must</em> be used, so as to ensure that all warnings reflect
+actual problems in the code.
<p>When a @SuppressWarnings annotation is necessary, it must be prefixed with
a TODO comment that explains the "impossible to eliminate" condition. This
will normally identify an offending class that has an awkward interface. For
example:</p>
-<pre><code>// TODO: The third-party class com.third.useful.Utility.rotate() needs generics
+<pre><code>// TODO: The third-party class com.third.useful.Utility.rotate() needs generics
@SuppressWarnings("generic-cast")
List<String> blix = Utility.rotate(blax);
</code></pre>
@@ -501,8 +506,10 @@
refactored to isolate the software elements where the annotation applies.</p>
</li>
</ul>
+
<h3 id="treat-acronyms-as-words">Treat Acronyms as Words</h3>
-<p>Treat acronyms and abbreviations as words in naming variables, methods, and classes. The names are much more readable:</p>
+<p>Treat acronyms and abbreviations as words in naming variables, methods, and
+classes to make names more readable:</p>
<table>
<thead>
<tr>
@@ -533,14 +540,14 @@
</tr>
</tbody>
</table>
-<p>Both the JDK and the Android code bases are very inconsistent with regards
-to acronyms, therefore, it is virtually impossible to be consistent with the
-code around you. Bite the bullet, and treat acronyms as words.</p>
+<p>As both the JDK and the Android code bases are very inconsistent around
+acronyms, it is virtually impossible to be consistent with the surrounding
+code. Therefore, always treat acronyms as words.</p>
<h3 id="use-todo-comments">Use TODO Comments</h3>
<p>Use TODO comments for code that is temporary, a short-term solution, or
-good-enough but not perfect.</p>
-<p>TODOs should include the string TODO in all caps, followed by a colon:</p>
+good-enough but not perfect. TODOs should include the string TODO in all caps,
+followed by a colon:</p>
<pre><code>// TODO: Remove this code after the UrlTable2 has been checked in.
</code></pre>
<p>and</p>
@@ -550,79 +557,67 @@
you either include a very specific date ("Fix by November 2005") or a very
specific event ("Remove this code after all production mixers understand
protocol V7.").</p>
+
<h3 id="log-sparingly">Log Sparingly</h3>
<p>While logging is necessary, it has a significantly negative impact on
-performance and quickly loses its usefulness if it's not kept reasonably
+performance and quickly loses its usefulness if not kept reasonably
terse. The logging facilities provides five different levels of logging:</p>
<ul>
-<li>
-<p><code>ERROR</code>:
-This level of logging should be used when something fatal has happened,
-i.e. something that will have user-visible consequences and won't be
-recoverable without explicitly deleting some data, uninstalling applications,
-wiping the data partitions or reflashing the entire phone (or worse). This
-level is always logged. Issues that justify some logging at the ERROR level
-are typically good candidates to be reported to a statistics-gathering
-server.</p>
+<li><code>ERROR</code>:
+Use when something fatal has happened, i.e. something will have user-visible
+consequences and won't be recoverable without explicitly deleting some data,
+uninstalling applications, wiping the data partitions or reflashing the entire
+device (or worse). This level is always logged. Issues that justify some logging
+at the ERROR level are typically good candidates to be reported to a
+statistics-gathering server.</li>
+<li><code>WARNING</code>:
+Use when something serious and unexpected happened, i.e. something that will
+have user-visible consequences but is likely to be recoverable without data loss
+by performing some explicit action, ranging from waiting or restarting an app
+all the way to re-downloading a new version of an application or rebooting the
+device. This level is always logged. Issues that justify some logging at the
+WARNING level might also be considered for reporting to a statistics-gathering
+server.</li>
+<li><code>INFORMATIVE:</code>
+Use note that something interesting to most people happened, i.e. when a
+situation is detected that is likely to have widespread impact, though isn't
+necessarily an error. Such a condition should only be logged by a module that
+reasonably believes that it is the most authoritative in that domain (to avoid
+duplicate logging by non-authoritative components). This level is always logged.
</li>
-<li>
-<p><code>WARNING</code>:
-This level of logging should used when something serious and unexpected
-happened, i.e. something that will have user-visible consequences but is
-likely to be recoverable without data loss by performing some explicit action,
-ranging from waiting or restarting an app all the way to re-downloading a new
-version of an application or rebooting the device. This level is always
-logged. Issues that justify some logging at the WARNING level might also be
-considered for reporting to a statistics-gathering server.</p>
-</li>
-<li>
-<p><code>INFORMATIVE:</code>
-This level of logging should used be to note that something interesting to
-most people happened, i.e. when a situation is detected that is likely to have
-widespread impact, though isn't necessarily an error. Such a condition should
-only be logged by a module that reasonably believes that it is the most
-authoritative in that domain (to avoid duplicate logging by non-authoritative
-components). This level is always logged.</p>
-</li>
-<li>
-<p><code>DEBUG</code>:
-This level of logging should be used to further note what is happening on the
-device that could be relevant to investigate and debug unexpected behaviors.
-You should log only what is needed to gather enough information about what is
-going on about your component. If your debug logs are dominating the log then
-you probably should be using verbose logging. </p>
-<p>This level will be logged, even
-on release builds, and is required to be surrounded by an <code>if (LOCAL_LOG)</code> or <code>if
-(LOCAL_LOGD)</code> block, where <code>LOCAL_LOG[D]</code> is defined in your class or
-subcomponent, so that there can exist a possibility to disable all such
-logging. There must therefore be no active logic in an <code>if (LOCAL_LOG)</code> block.
-All the string building for the log also needs to be placed inside the <code>if
+<li><code>DEBUG</code>:
+Use to further note what is happening on the device that could be relevant to
+investigate and debug unexpected behaviors. You should log only what is needed
+to gather enough information about what is going on about your component. If
+your debug logs are dominating the log then you probably should be using verbose
+logging.
+<p>This level will be logged, even on release builds, and is required to be
+surrounded by an <code>if (LOCAL_LOG)</code> or <code>if (LOCAL_LOGD)</code>
+block, where <code>LOCAL_LOG[D]</code> is defined in your class or subcomponent,
+so that there can exist a possibility to disable all such logging. There must
+therefore be no active logic in an <code>if (LOCAL_LOG)</code> block. All the
+string building for the log also needs to be placed inside the <code>if
(LOCAL_LOG)</code> block. The logging call should not be re-factored out into a
method call if it is going to cause the string building to take place outside
-of the <code>if (LOCAL_LOG)</code> block. </p>
-<p>There is some code that still says <code>if
-(localLOGV)</code>. This is considered acceptable as well, although the name is
-nonstandard.</p>
+of the <code>if (LOCAL_LOG)</code> block.</p>
+<p>There is some code that still says <code>if (localLOGV)</code>. This is
+considered acceptable as well, although the name is nonstandard.</p>
</li>
-<li>
-<p><code>VERBOSE</code>:
-This level of logging should be used for everything else. This level will only
-be logged on debug builds and should be surrounded by an <code>if (LOCAL_LOGV)</code> block
-(or equivalent) so that it can be compiled out by default. Any string building
-will be stripped out of release builds and needs to appear inside the <code>if (LOCAL_LOGV)</code> block.</p>
+<li><code>VERBOSE</code>:
+Use for everything else. This level will only be logged on debug builds and
+should be surrounded by an <code>if (LOCAL_LOGV)</code> block (or equivalent) so
+it can be compiled out by default. Any string building will be stripped out of
+release builds and needs to appear inside the <code>if (LOCAL_LOGV)</code> block.
</li>
</ul>
<p><em>Notes:</em> </p>
<ul>
-<li>
-<p>Within a given module, other than at the VERBOSE level, an
-error should only be reported once if possible: within a single chain of
+<li>Within a given module, other than at the VERBOSE level, an
+error should only be reported once if possible. Within a single chain of
function calls within a module, only the innermost function should return the
error, and callers in the same module should only add some logging if that
-significantly helps to isolate the issue.</p>
-</li>
-<li>
-<p>In a chain of modules, other than at the VERBOSE level, when a
+significantly helps to isolate the issue.</li>
+<li>In a chain of modules, other than at the VERBOSE level, when a
lower-level module detects invalid data coming from a higher-level module, the
lower-level module should only log this situation to the DEBUG log, and only
if logging provides information that is not otherwise available to the caller.
@@ -634,101 +629,76 @@
framework should not trigger logging higher than the DEBUG level. The only
situations that should trigger logging at the INFORMATIVE level or higher is
when a module or application detects an error at its own level or coming from
-a lower level.</p>
-</li>
-<li>
-<p>When a condition that would normally justify some logging is
+a lower level.</li>
+<li>When a condition that would normally justify some logging is
likely to occur many times, it can be a good idea to implement some
rate-limiting mechanism to prevent overflowing the logs with many duplicate
-copies of the same (or very similar) information.</p>
-</li>
-<li>
-<p>Losses of network connectivity are considered common and fully
-expected and should not be logged gratuitously. A loss of network connectivity
+copies of the same (or very similar) information.</li>
+<li>Losses of network connectivity are considered common, fully expected, and
+should not be logged gratuitously. A loss of network connectivity
that has consequences within an app should be logged at the DEBUG or VERBOSE
level (depending on whether the consequences are serious enough and unexpected
-enough to be logged in a release build).</p>
-</li>
-<li>
-<p>A full filesystem on a filesystem that is accessible to or on
+enough to be logged in a release build).</li>
+<li>A full filesystem on a filesystem that is accessible to or on
behalf of third-party applications should not be logged at a level higher than
-INFORMATIVE.</p>
-</li>
-<li>
-<p>Invalid data coming from any untrusted source (including any
+INFORMATIVE.</li>
+<li>Invalid data coming from any untrusted source (including any
file on shared storage, or data coming through just about any network
connections) is considered expected and should not trigger any logging at a
level higher then DEBUG when it's detected to be invalid (and even then
-logging should be as limited as possible).</p>
-</li>
-<li>
-<p>Keep in mind that the <code>+</code> operator, when used on Strings,
+logging should be as limited as possible).</li>
+<li>Keep in mind that the <code>+</code> operator, when used on Strings,
implicitly creates a <code>StringBuilder</code> with the default buffer size (16
-characters) and potentially quite a few other temporary String objects, i.e.
+characters) and potentially other temporary String objects, i.e.
that explicitly creating StringBuilders isn't more expensive than relying on
-the default '+' operator (and can be a lot more efficient in fact). Also keep
-in mind that code that calls <code>Log.v()</code> is compiled and executed on release
-builds, including building the strings, even if the logs aren't being
-read.</p>
-</li>
-<li>
-<p>Any logging that is meant to be read by other people and to be
+the default '+' operator (and can be a lot more efficient in fact). Keep
+in mind that code that calls <code>Log.v()</code> is compiled and executed on
+release builds, including building the strings, even if the logs aren't being
+read.</li>
+<li>Any logging that is meant to be read by other people and to be
available in release builds should be terse without being cryptic, and should
be reasonably understandable. This includes all logging up to the DEBUG
-level.</p>
-</li>
-<li>
-<p>When possible, logging should be kept on a single line if it
+level.</li>
+<li>When possible, logging should be kept on a single line if it
makes sense. Line lengths up to 80 or 100 characters are perfectly acceptable,
while lengths longer than about 130 or 160 characters (including the length of
-the tag) should be avoided if possible.</p>
-</li>
-<li>
-<p>Logging that reports successes should never be used at levels
-higher than VERBOSE.</p>
-</li>
-<li>
-<p>Temporary logging that is used to diagnose an issue that's
-hard to reproduce should be kept at the DEBUG or VERBOSE level, and should be
-enclosed by if blocks that allow to disable it entirely at compile-time.</p>
-</li>
-<li>
-<p>Be careful about security leaks through the log. Private
+the tag) should be avoided if possible.</li>
+<li>Logging that reports successes should never be used at levels
+higher than VERBOSE.</li>
+<li>Temporary logging used to diagnose an issue that is hard to reproduce should
+be kept at the DEBUG or VERBOSE level and should be enclosed by if blocks that
+allow for disabling it entirely at compile time.</li>
+<li>Be careful about security leaks through the log. Private
information should be avoided. Information about protected content must
definitely be avoided. This is especially important when writing framework
code as it's not easy to know in advance what will and will not be private
-information or protected content.</p>
-</li>
-<li>
-<p><code>System.out.println()</code> (or <code>printf()</code> for native code) should
-never be used. System.out and System.err get redirected to /dev/null, so your
-print statements will have no visible effects. However, all the string
-building that happens for these calls still gets executed.</p>
-</li>
-<li>
-<p><em>The golden rule of logging is that your logs may not
+information or protected content.</li>
+<li><code>System.out.println()</code> (or <code>printf()</code> for native code)
+should never be used. System.out and System.err get redirected to /dev/null, so
+your print statements will have no visible effects. However, all the string
+building that happens for these calls still gets executed.</li>
+<li><em>The golden rule of logging is that your logs may not
unnecessarily push other logs out of the buffer, just as others may not push
-out yours.</em></p>
-</li>
+out yours.</em></li>
</ul>
+
<h3 id="be-consistent">Be Consistent</h3>
<p>Our parting thought: BE CONSISTENT. If you're editing code, take a few
-minutes to look at the code around you and determine its style. If they use
-spaces around their if clauses, you should too. If their comments have little
-boxes of stars around them, make your comments have little boxes of stars
+minutes to look at the surrounding code and determine its style. If that code
+uses spaces around the if clauses, you should too. If the code comments have
+little boxes of stars around them, make your comments have little boxes of stars
around them too.</p>
<p>The point of having style guidelines is to have a common vocabulary of
coding, so people can concentrate on what you're saying, rather than on how
you're saying it. We present global style rules here so people know the
-vocabulary. But local style is also important. If code you add to a a file
+vocabulary, but local style is also important. If the code you add to a file
looks drastically different from the existing code around it, it throws
-readers out of their rhythm when they go to read it. Try to avoid this.</p></p>
+readers out of their rhythm when they go to read it. Try to avoid this.</p>
+
<h2 id="javatests-style-rules">Javatests Style Rules</h2>
-<h3 id="follow-test-method-naming-conventions">Follow Test Method Naming Conventions</h3>
-<p>When naming test methods, you can use an underscore to separate what is
-being tested from the specific case being tested. This style makes it easier
-to see exactly what cases are being tested.</p>
-<p>For example:</p>
+<p>Follow test method naming conventions and use an underscore to separate what
+is being tested from the specific case being tested. This style makes it easier
+to see exactly what cases are being tested. For example:</p>
<pre><code>testMethod_specificCase1 testMethod_specificCase2
void testIsDistinguishable_protanopia() {
@@ -736,4 +706,4 @@
assertFalse(colorMatcher.isDistinguishable(Color.RED, Color.BLACK))
assertTrue(colorMatcher.isDistinguishable(Color.X, Color.Y))
}
-</code></pre>
+</code></pre>
\ No newline at end of file
diff --git a/src/source/source_toc.cs b/src/source/source_toc.cs
index d0e1c68..66b5177 100644
--- a/src/source/source_toc.cs
+++ b/src/source/source_toc.cs
@@ -73,7 +73,7 @@
<li><a href="http://android-review.googlesource.com">View Patches</a></li>
<li><a href="<?cs var:toroot ?>source/life-of-a-bug.html">Life of a Bug</a></li>
<li><a href="<?cs var:toroot ?>source/report-bugs.html">Reporting Bugs</a></li>
- <li><a href="<?cs var:toroot ?>source/code-style.html">Code Style Guidelines</a></li>
+ <li><a href="<?cs var:toroot ?>source/code-style.html">Code Style Rules</a></li>
</ul>
</li>
