RefEqBoxed.qhelp

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


<overview>
<p>Comparing two boxed primitive values using <code>==</code> or
<code>!=</code> compares object identity, which may not be intended.</p>

</overview>
<recommendation>

<p>Usually, you should compare non-primitive objects, for example boxed primitive values, by using 
their <code>equals</code> methods.</p>

</recommendation>
<example>

<p>With the following definition, the method call <code>refEq(new Integer(2), new Integer(2))</code> returns <code>false</code> 
because the objects are not identical.</p>

<sample src="RefEqBoxedBad.java" />

<p>With the following definition, the method call <code>realEq(new Integer(2), new Integer(2))</code> 
returns <code>true</code> because the objects contain equal values.</p>

<sample src="RefEqBoxed.java" />

</example>
<references>


<li>
  J. Bloch and N. Gafter, <em>Java Puzzlers: Traps, Pitfalls, and Corner Cases</em>, Puzzle 32. Addison-Wesley, 2005.
</li>
<li>
  Java API Specification:
  <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#equals(java.lang.Object)">Object.equals()</a>,
  <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Integer.html#equals(java.lang.Object)">Integer.equals()</a>.
</li>


</references>
</qhelp>