BreakInSwitchCase.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>


<overview>
<p>In a <code>switch</code> statement, execution 'falls through' from one <code>case</code> to
the next, unless the <code>case</code> ends with a <code>break</code> statement. A
common programming error is to forget to insert a <code>break</code> at the end
of a <code>case</code>.</p>

</overview>
<recommendation>

<p>End each <code>case</code> with a <code>break</code> statement or, if execution is 
supposed to fall through to the next <code>case</code>, comment the last line of the
<code>case</code> with the following comment: <code>/* falls through */</code></p>

<p>Such comments are not required for a completely empty <code>case</code> that is
supposed to share the same implementation with the subsequent <code>case</code>.</p>

</recommendation>
<example>

<p>In the following example, the <code>PING</code> case is missing a
<code>break</code> statement. As a result, after <code>reply</code> is assigned the value of 
<code>Message.PONG</code>, execution falls through to the <code>TIMEOUT</code> case. Then the value 
of <code>reply</code> is erroneously assigned the value of <code>Message.PING</code>. To fix this,
insert <code>break;</code> at the end of the <code>PING</code> case.</p>

<sample src="BreakInSwitchCase.java" />


</example>
<references>


<li>
  J. Bloch and N. Gafter, <em>Java Puzzlers: Traps, Pitfalls, and Corner Cases</em>, Puzzle 23.
  Addison-Wesley, 2005.
</li>
<li>
Code Conventions for the Java Programming Language:
<a href="https://www.oracle.com/java/technologies/javase/codeconventions-statements.html#468">7.8 switch Statements</a>.
</li>
<li>
Help - Eclipse Platform:
<a href="https://help.eclipse.org/2020-12/advanced/content.jsp?topic=/org.eclipse.jdt.doc.user/reference/preferences/java/compiler/ref-preferences-errors-warnings.htm">Java Compiler Errors/Warnings Preferences</a>.
</li>


</references>
</qhelp>