1<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 2 3<html> 4 5<head> 6<title>check-cast</title> 7<link rel=stylesheet href="opcode.css"> 8</head> 9 10<body> 11 12<h1>check-cast</h1> 13 14<h2>Purpose</h2> 15 16<p> 17Throw if the reference in the given register cannot be cast to the indicated 18type. The type must be a reference type (not a primitive type). 19</p> 20 21<h2>Details</h2> 22 23<table class="instruc"> 24<thead> 25<tr> 26 <th>Op & Format</th> 27 <th>Mnemonic / Syntax</th> 28 <th>Arguments</th> 29</tr> 30</thead> 31<tbody> 32<tr> 33 <td>1f 21c</td> 34 <td>check-cast vAA, type@BBBB</td> 35 <td><code>A:</code> reference-bearing register (8 bits)<br/> 36 <code>B:</code> type index (16 bits)</td> 37</tr> 38</tbody> 39</table> 40 41<h2>Constraints</h2> 42 43<ul> 44 <li> 45 A must be a valid register index in the current stack frame. 46 </li> 47 <li> 48 Register vA must contain a reference value. 49 </li> 50 <li> 51 B must be a valid index into the type pool. 52 </li> 53 <li> 54 Type pool entry B must contain a valid type descriptor for a reference type. 55 </li> 56</ul> 57 58<h2>Behavior</h2> 59 60<ul> 61 <li> 62 An attempt is made to get a reference to the class C the name of which is 63 contained in type pool entry B. 64 </li> 65 <li> 66 If C has not been loaded and resolved before, it is being loaded and 67 resolved. All exceptions that are possible during class loading can occur at 68 this point. 69 </li> 70 <li> 71 The run-time type of the object reference vA is compared against C. 72 <ul> 73 <li> 74 If vA is null, the instruction succeeds (without further effects). 75 </li> 76 <li> 77 If vA is assignment compatible with C according to the usual rules of 78 the Java programming language, the instruction succeeds (without further 79 effects). 80 </li> 81 </ul> 82 </li> 83</ul> 84 85<h2>Exceptions</h2> 86 87<ul> 88 <li> 89 ClassCastException is thrown if vA is either not null or not assignment 90 compatible with C. 91 </li> 92</ul> 93 94</body> 95</html> 96