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<html><head><title>VM Spec </title></head><body BGCOLOR=#eeeeff text=#000000 LINK=#0000ff VLINK=#000077 ALINK=#ff0000> <a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc144.html">Prev</a> | <a href="Instructions2.doc146.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><hr><br> <a name="lookupswitch"></a><h2>lookupswitch</h2><a name="69547"></a>The table <i>match</i>-<i>offset</i> pairs of the <i>lookupswitch</i> instruction must be sorted in increasing numerical order by <i>match</i>.<p><a name="69548"></a>The <i>key</i> must be of type <code>int</code> and is popped from the operand stack. The <i>key</i> is compared against the <i>match</i> values. If it is equal to one of them, then a target address is calculated by adding the corresponding <i>offset</i> to the address of the opcode of this <i>lookupswitch</i> instruction. If the <i>key</i> does not match any of the <i>match</i> values, the target address is calculated by adding <i>default</i> to the address of the opcode of this <i>lookupswitch</i> instruction. Execution then continues at the target address.<p><a name="69549"></a>The target address that can be calculated from the offset of each <i>match-offset</i> pair, as well as the one calculated from <i>default</i>, must be the address of an opcode of an instruction within the method that contains this <i>lookupswitch</i> instruction.<p><a name="lookupswitch.Notes"></a><b>Notes</b><br><a name="69550"></a>The alignment required of the 4-byte operands of the <i>lookupswitch</i> instruction guarantees 4-byte alignment of those operands if and only if the method that contains the <i>lookupswitch</i> is positioned on a 4-byte boundary.<p><a name="69551"></a>The <i>match-offset</i> pairs are sorted to support lookup routines that are quicker than linear search.<p><hr><!-- This inserts footnotes--><p><a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc144.html">Prev</a> | <a href="Instructions2.doc146.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><p><font size=-1>Java Virtual Machine Specification (HTML generated by dkramer on February 25, 1997)<br><i><a href="Copyright.doc.html">Copyright © 1996 Sun Microsystems, Inc.</a>All rights reserved</i><br>Please send any comments or corrections to <a href="mailto:doug.kramer@sun.com">doug.kramer@sun.com</a></font></body></html>⌨️ 快捷键说明
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