Editing Java virtual machine (section)

===Bytecode interpreter and just-in-time compiler===
For each [[hardware architecture]] a different Java bytecode [[Interpreter (computing)|interpreter]] is needed. When a computer has a Java bytecode interpreter, it can run any Java bytecode program, and the same program can be run on any computer that has such an interpreter.

When Java bytecode is executed by an interpreter, the execution will always be slower than the execution of the same program compiled into native machine language. This problem is mitigated by [[Just-in-time compilation|just-in-time (JIT) compilers]] for executing Java bytecode. A JIT compiler may translate Java bytecode into native machine language while executing the program. The translated parts of the program can then be executed much more quickly than they could be interpreted. This technique gets applied to those parts of a program frequently executed. This way a JIT compiler can significantly speed up the overall execution time.

There is no necessary connection between the Java programming language and Java bytecode. A program written in Java can be compiled directly into the machine language of a real computer and programs written in other languages than Java can be compiled into Java bytecode.

Java bytecode is intended to be platform-independent and secure.<ref>David J. Eck, ''[http://math.hws.edu/javanotes/c1/s3.html Introduction to Programming Using Java] {{Webarchive|url=https://web.archive.org/web/20141011192544/http://math.hws.edu/javanotes/c1/s3.html |date=2014-10-11 }}'', Seventh Edition, Version 7.0, August 2014 at Section 1.3 "The Java Virtual Machine"</ref> Some JVM implementations do not include an interpreter, but consist only of a just-in-time compiler.<ref>''[http://docs.oracle.com/cd/E15289_01/doc.40/e15058/underst_jit.htm Oracle JRockit Introduction] {{Webarchive|url=https://web.archive.org/web/20150906145705/http://docs.oracle.com/cd/E15289_01/doc.40/e15058/underst_jit.htm |date=2015-09-06 }}'' Release R28 at 2. "Understanding Just-In-Time Compilation and Optimization"</ref>