[haimez]

Java is both compiled (first to bytecode, then to machine code by the JIT) and fast (once JIT compiled).

[jandrewrogers]

It depends on what you are using it for, “fast” is relative. Java can be fast for applications where performance and scalability are not a primary features. If performance and scalability are core objectives, even performance-engineered Java isn’t really competitive with a systems language. You can bend Java to make it perform better than most people believe, especially today, but the gap is still pretty large in practice.

I wrote performance-engineered Java for years. Even getting it to within 2x worse than performance-engineered C++ took heroic efforts and ugly Java code.

[Raidion]

Java is "fast" but not fast. Most of the time if performance is a true concern, you are not writing code in Java.

[frollogaston]

I have yet to run a Java program that I haven't had to later kill due to RAM exhaustion. I don't know why. Yeah an Integer takes 160 bits and that's without the JVM overhead, but still. Somehow it feels like Java uses even more memory than Python. Logically you'd point the finger at whoever wrote the software rather than the language/runtime itself, but somehow it's always Java. It's like the Prius of languages.

Ok, just glanced at my corp workstation and some Java build analysis server is using 25GB RES, 50GB VIRT when I have no builds going. The hell is it doing.

[lmm]

Java is fast for long-running server processes. Even HFT shops competing for milliseconds use it. But yeah every user-facing interactive Java application manages to feel clunky.