IncomparableEquals.qhelp

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


<overview>
<p>Calls of the form <code>x.equals(y)</code>,
where <code>x</code> and <code>y</code> have incomparable types,
should always return <code>false</code> because the runtime types 
of <code>x</code> and <code>y</code> will be different. 
Two types are incomparable if they are distinct
and do not have a common subtype.</p>

</overview>
<recommendation>

<p>Ensure that such comparisons use comparable types.</p>

</recommendation>
<example>

<p>In the following example, the call to <code>equals</code> on line 5 refers to the whole array by
mistake, instead of a specific element. Therefore, "Value not found" is returned.</p>

<sample src="IncomparableEquals.java" />

</example>
<references>


<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>.
</li>


</references>
</qhelp>