Java bytecode: Difference between revisions

Revision as of 05:10, 7 August 2014

Revision as of 12:44, 13 August 2014

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== Relation to Java ==

A [[Java (programming language)|Java]] programmer does not need to be aware of or understand Java bytecode at all. However, as suggested in the [[IBM]] developerWorks journal, "Understanding bytecode and what bytecode is likely to be generated by a [[Java compiler]] helps the Java programmer in the same way that knowledge of [[assembly Language|assembly]] helps the [[C (programming language)|C]] or [[C++]] programmer."<ref>[http://www.ibm.com/developerworks/ibm/library/it-haggar_bytecode/ Understanding bytecode makes you a better programmer]</ref>

== Instructions ==

{{See also|Java bytecode instruction listings}}

As each byte has 256 potential values, there are 256 possible opcodes. Of these, <code>0x00</code> through <code>0xca</code>, <code>0xfe</code>, and <code>0xff</code> are assigned values. <code>0xca</code> is reserved as a breakpoint instruction for Java debuggers and its type is not used by the language. Similarly, <code>0xfe</code> and <code>0xff</code> are not used by the language and are reserved for internal use by the Java virtual machine.

Instructions fall into a number of broad groups: