Eric the Red

Now i'm new to java just learning it in school right now and i want to know why is it slower than c++?? now with c++ you declare memory on the stack while in java i don't think you can. Is that the primary reasson that it is slower?

Has it to do with the fact that java is an interpreted language while c++ isn't. Please can someone explain this to me.

Sorry for the newb question.

Jimbo

It's mainly about Java being interpreted whereas C++ is compiled.

xavier

http://www.idiom.com/~zilla/Computer...benchmark.html
The : "Java is slow" - is becoming more and more an "urban mith" so to speak. Yes, an application starts slower with java, but from then one, the differences aren't that greate.
And with each new jdk version, things are getting faster.

http://www.javaworld.com/jw-02-1998/jw-02-jperf.html

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grumpy

Java being slower than C++ is no urban myth. There are some cases where well written Java code can out-perform well written C++ code, but they're exceptions rather than the rule. Things like JIT in Java can give better performance, if your code does things over and over, as your code is optimised to run faster when it is run more often, but YMMV as to what code it works well with and what gains you get because it relies on internals of the virtual machine.

The JVM (which interprets Java byte codes) is a performance bottleneck for a Java program, although techniques like JIT do improve things a lot but that depends on the implementation of the virtual machine. C++ does not have a virtual machine, so no such bottleneck exists --- the primary bottleneck on performance of a C++ program is always quality of the code and libraries the program used. Java still has that bottleneck. A high quality C++ compiler optimises for the target machine, which a Java compiler does not. JIT can achieve the same effect for Java (and potentially do a better job as it occurs at run time, so can optimise execution to address actual hotspots in code) but JIT functionality is at least as difficult to implement well as high quality compiler optimiser.

Jimbo

I stand somewhat corrected. I did find this humorous though:
I'm slightly curious on the age of the second article however; they specify their tests as being done using VC++ 5.0 and Java 1.1.5, both of which are severely outdated by now, and I'm assuming that VC++ 5.0 was as bad if not worse than VC++ 6.0 at following the standard.

However, both articles were interesting, especially the first.

jaeusm

Inspecting the URL of the second article leads me to believe it was written in 1998

ReggaetonKing

Java is compiled into machince language and then the JVM runs the machine code and executes the program, a lot of people say Java is slower than C++ but also its been proven that its actually if anything a little faster than C++, I've read a lot of documentations on Java and C++ and then average out on run-time!

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hoffmandirt

Actually isn't java compiled into java byte code and then interpreted by the jvm? I know there are compilers that convert it into native code, but I was under the impression that the jvm interprets the byte code, not native code.

Arevos

This is incorrect, I'm afraid. Java compiles to Java bytecode, as hoffmandirt rightly points out. Java bytecode is architecture independant, and is interpreted by the JVM (Java Virtual Machine). C++, on the other hand, is compiled into native machine code, and can be executed without a virtual machine.

Java bytecode has the advantage of being platform independant. With Java, you don't have to worry what machine you're programming on, and you don't have to worry about library or DLL conflicts - if the JVM runs, your program will probably run, too.

C++ has the advantage of being faster, because it cuts out the JVM middleman, and in many cases more memory efficient, as JVM instances can't share libraries, IIRC, whilst C++ programs do this all the time.

Java isn't going to be faster than C++, because the JVM slows it down. Java may have some more efficiently programmed libraries than C++, but that's another story altogether. In general, Java is several times slower than C++.

DaWei

Funny how "urban myths" come about because a machine runs at 3 GHz instead of 2 MHz. Nothing real about that chit, of course.

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