Re: Write once, run anywhere?

From:

Joshua Cranmer <Pidgeot18@verizon.net>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 23 Jun 2007 16:06:41 GMT

Message-ID:

<lybfi.416$RZ1.280@trnddc05>

On Sat, 23 Jun 2007 12:46:40 -0300, JT wrote:

The JVM is what processes byte-code which is compiled Java code
(classes)? Let's say we have two operating systems, x and y. OS x has a
way to oh say... open the CD tray. OS y does not. So would a JVM
running on x include an implementation of the openCDTray and y would
not, or would it be excluded on both since it's not a common function?
This would mean that the JVM is an implementation of the base operating
system level calls... with me so far...I'm probably off in left field
somewhere... but...

Look in the Java API. Do you see any method named "openCDTray" or
anything similar? No. One would have to find a library with the
appropriate JNI bindings to run "openCDTray" because it will be assumed
that no JVM will have the proper implementation.

Now lets say "Peter Programmer" has been given the assignment of writing
a Java GUI that will let the user press a button, and the CD tray will
open. How would Peter write this code once and have it run on an OS
that does not have an implementation for opening the CD tray, whether by
design (ie. a dumb terminal) or not.

Graceful failure when loading JNI bindings.