Why is Java startup so slow?

Question

Does anyone know why Java startup is so slow? Compared to other interpreted languages like Javascript and Perl, they run much faster. And can someone get technical with me? (But without pointing me to the JVM specification, which I don't understand.) It use to take longer for me to load Mozilla0.9 than a Java applet, but now Mozilla1.3 loads faster than a Java applet.

Answer 1

"Connector" is a rather ill-defined way of describing
it, which is why I chose the word -- to easily deflect
further inquiries to quantify. ;>
In a slightly more specific way, on start-up JVM needs
to (not necessarily in order, 'cause I don't know the
exact order) at the very minimum:
1. Allocate memory.
2. Query OS for a minimal set of needed facilities.
3. Allocate memory. Allocate allocated memory
(internally, for use by itself and the application).
4. Map the OS facilities to Java facilities. (This is
what I meant by "connectors").
5. Allocate memory. Allocate allocated memory.
6. Set up the internal control -- security managers,
thread scheduler, gc, classloaders, calling stacks,
virtual lookup tables, etcetc.
Some of the above don't apply to applets.
Thanks for the tip on 1.4.2beta. I'll give it a try. I
assume you meant startup speed?All this is almost instant you realize. The real time it takes to start your program is that it takes much longer for Java classes to be loaded.
The startup time is proportional to the number of classes you need to load to get your program running. If you only are writing a simple, console based java program the startup time will be much less then if you load a Swing application. Swing by itself is a huge number of classes, and then you have to load your classes. So it can take awhile.
All the things you mention, every program has to do and the code that the JVM uses must be written in C or some other systems language.
One reason at least on my machine that java startup is slow is that I have a slow hard drive. On my home machine, java is much faster around twice as fast to startup, but the processor and ram are not twice as good. I think that it's because the hard drive is faster. Because most of the time it's waiting for data from the disk and the Java enviroment has the disadvantage that it's very large on disk.