I don't know the answer to your question. I'm no CS expert, but based on my experience, Java is indeed oftentimes slow.
Based on what experience ? Again, which Java ? Here are the choices :
- Java the Virtual Machine
- Java the platform
- Java the language.
If you don't know the answer to this, you cannot claim Java is indeed often times slow with any kind of credibility.
I do admit, I do not know a great deal about Android development, but it's my understanding that the Android SDK compiles the Java code into native code, reducing the overhead required by traditional Java VMs to translate the byte code into native machine code for that platform - in other words, even though an Android application is written in Java, and Java is traditionally cross platform, you can't run an Android application in a Java VM on your Windows or Mac computer, it would require emulation. So the problems traditionally associated with Java don't exist on Android.
Indeed, your understanding is not wrong. Android uses 1 1/2 part of Java. They have the language, that much is evident and they are getting sued over it to boot. They are also using the platform somewhat, in that they have incorporated parts of Apache Harmony for J2SE compatibility. However, their main platform is not J2SE, it's Android. Apps will be written against Android and not Harmony for the most part.
Harmony is also a complete independant rewrite of the J2SE platform, free from any SUN code. I doubt the poster named (marc) has any experience with it if he wants to claim the platform is slow. He would then be talking about Sun's platform, which is far from slow.
The part they aren't using, and the part most often responsible for performance problems, is the VM itself. Sun's JVM is anything but slow nowadays, thanks to advances like the JIT compiler and other optimizations, but that's a none issue, Android uses Dalvik, a very performant VM that is not a Java Virtual Machine. It does not read in Java bytecode at all, it reads in a native Dalvik bytecode, which is what your Android app gets compiled to by the Android SDK. It's a complete ground up rewrite that is completely independant of code shipped by Sun.
As such, the poster was wrong on all accounts. He simply repeated a stereotype that doesn't even apply and hoped no one would notice. FUD if you like.