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>monitor-exit</title> 7 <link rel=stylesheet href="opcode.css"> 8 </head> 9 10 <body> 11 12 <h1>monitor-exit</h1> 13 14 <h2>Purpose</h2> 15 16 <p> 17 Release the monitor for the indicated object. 18 </p> 19 <p> 20 Note: If this instruction needs to throw an exception, it must do so as if the 21 pc has already advanced past the instruction. It may be useful to think of this 22 as the instruction successfully executing (in a sense), and the exception 23 getting thrown after the instruction but before the next one gets a chance to 24 run. This definition makes it possible for a method to use a monitor cleanup 25 catch-all (e.g., finally) block as the monitor cleanup for that block itself, 26 as a way to handle the arbitrary exceptions that might get thrown due to the 27 historical implementation of Thread.stop(), while still managing to have proper 28 monitor hygiene. 29 </p> 30 31 <h2>Details</h2> 32 33 <table class="instruc"> 34 <thead> 35 <tr> 36 <th>Op & Format</th> 37 <th>Mnemonic / Syntax</th> 38 <th>Arguments</th> 39 </tr> 40 </thead> 41 <tbody> 42 <tr> 43 <td>1e 11x</td> 44 <td>monitor-exit vAA</td> 45 <td><code>A:</code> reference-bearing register (8 bits)</td> 46 </tr> 47 </tbody> 48 </table> 49 50 <h2>Constraints</h2> 51 52 <ul> 53 <li> 54 A must be a valid register index for the current stack frame. 55 </li> 56 <li> 57 Register vA must contain a reference to an object. 58 </li> 59 </ul> 60 61 <h2>Behavior</h2> 62 63 <ul> 64 <li> 65 An attempt is made for the current thread to release the monitor of the 66 indicated object. 67 </li> 68 <li> 69 If the current thread is the owner, the following happens: 70 <ul> 71 <li> 72 The monitor's entry count is decreased by one. 73 </li> 74 <li> 75 If the entry count has reached zero, the monitor is released. Other 76 threads waiting for the same monitor have a chance to acquire it. 77 </li> 78 </ul> 79 </li> 80 <li> 81 Any exception that gets thrown by this instruction bears the PC of the 82 instruction following the monitor-exit. That is, from the point of view of 83 an exception handler it cannot be distinguished from the same type of 84 exception being thrown immediately after the monitor-exit instruction. 85 </li> 86 </ul> 87 88 <h2>Exceptions</h2> 89 90 <ul> 91 <li> 92 NullPointerException is thrown if vA is null. 93 </li> 94 <li> 95 IllegalMonitorStateException is thrown if the current thread is not the 96 owner of that monitor. 97 </li> 98 </ul> 99 100 </body> 101 </html> 102
