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<title>check-cast</title>
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<h1>check-cast</h1>
<h2>Purpose</h2>
<p>
Throw if the reference in the given register cannot be cast to the indicated
type. The type must be a reference type (not a primitive type).
</p>
<h2>Details</h2>
<table class="instruc">
<thead>
<tr>
<th>Op & Format</th>
<th>Mnemonic / Syntax</th>
<th>Arguments</th>
</tr>
</thead>
<tbody>
<tr>
<td>1f 21c</td>
<td>check-cast vAA, type@BBBB</td>
<td><code>A:</code> reference-bearing register (8 bits)<br/>
<code>B:</code> type index (16 bits)</td>
</tr>
</tbody>
</table>
<h2>Constraints</h2>
<ul>
<li>
A must be a valid register index in the current stack frame.
</li>
<li>
Register vA must contain a reference value.
</li>
<li>
B must be a valid index into the type pool.
</li>
<li>
Type pool entry B must contain a valid type descriptor for a reference type.
</li>
</ul>
<h2>Behavior</h2>
<ul>
<li>
An attempt is made to get a reference to the class C the name of which is
contained in type pool entry B.
</li>
<li>
If C has not been loaded and resolved before, it is being loaded and
resolved. All exceptions that are possible during class loading can occur at
this point.
</li>
<li>
The run-time type of the object reference vA is compared against C.
<ul>
<li>
If vA is null, the instruction succeeds (without further effects).
</li>
<li>
If vA is assignment compatible with C according to the usual rules of
the Java programming language, the instruction succeeds (without further
effects).
</li>
</ul>
</li>
</ul>
<h2>Exceptions</h2>
<ul>
<li>
ClassCastException is thrown if vA is either not null or not assignment
compatible with C.
</li>
</ul>
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