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| <head> |
| <title>check-cast</title> |
| <link rel=stylesheet href="opcode.css"> |
| </head> |
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| <body> |
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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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