Hacker News Reader

Comment by ludovicianul | Hacker News Reader

I'm always amazed by how much thinking and work the Java leads put in rolling out changes that move the language forward, but make it backward compatible as much as possible.

View on HN

Rhis is the correct way to do it in enterprise environments.

C++ gets a lotof rage for doing the same thing.

The last thing you want in an enterprise environment is that your working code breaks and you have to commit more time to things that were working before.

What I do like about java is that when breaking changes must happen (and they do occasionally), they are almost always small and the java authors signpost it WELL in advance of making the break.

For example, this is technically legal in Java and will probably work today. Both foo and bar will synchronize on the same referenced object due to the integer cache.

This is something that will break when value types land for real.

    void foo() {
      Integer i = 1;
      synchronized(i) {
        doEvil();
      }
    }
    
    void bar() {
      Integer i = 1;
      synchronized(i) {
        doEvil();
      }
    }

Yes. Having a strong spec helps also in general.

I think that, with all things on the table, backwards compatibility, a spec and, where things are broken things are signaled should be the standard for enterprise grade non-toy apps.

Of course, breaking something should be kept to the minimum.

That is why I keep using C++ and, if I have to do backend in the future for webs, I will probably choose Java over C#: stable, multi-vendor, will work in 10 years, stable.

Agreed. I'm just happy that Java is willing to make a break when necessary. They do an excellent job of avoiding it at all costs but they won't nuke a very needed feature (like value types) if they can't deliver it without making some small breaks.

You can be pretty sure that a jar compiled for Java 1.0 will work on a Java 25 VM, and that's pretty great.

Whatever Java is doing seems a few orders of magnitude smoother and saner than C++ (and I like C++).

It depends on how you look at it.

C++ is very different since it is native.

Java is a VM.

This affects lots of decisions in weird ways.

But in essence both commit to backwards stability at the end.

C++ goes for performance, JVM for a more full-featured bytecode vm, etc. but still.

None of that prevents Java from blowing up their language with complex features. They are somehow able to sit back and work on proposals for years and end up with what makes sense for the language.

One thing the Java architects have said is they let most of the complex feature development happen outside of Java, which is pretty nice.

They let the likes of Kotlin, C#, C++, Scala, Haskell, etc all explore their own little features then they figure out if it could be integrated with Java and what it'd look like.

I really like that approach because it's slow, methodical, and the features typically are very well aligned with Java. None of them feel particularly out of place.

Java's preview system also works pretty well to get these features refined over time.

The JVM goes for performance, too, only with an emphasis on the performance of larger programs. It's designed to address some of the serious performance issues that large C++ programs tend to suffer from (I originally made the switch to Java because it was getting hard to keep the large C++ applications we were working on fast enough; Java does some optimisations that are hard for a C++ compiler).

Well, yes. True that for long-running apps JVM seems to be tuned.

I meant the kind of "perf-to-the-instruction" thst native can generate vs other considerations.

One thing we C++ programmers know, though, is that direct control over instructions helps performance in small programs but can hurt it in larger programs. E.g. it is really hard to enjoy the performance benefits that moving collectors and JITs can bring in large C++ applications.

I am not sure of the real life difference of this. You can tweak C++ a lot, you can make caches, etc your own with memoization and others.

True that you would need to build it by hand and, at that time, maybe it is better to just pick something tried and tested for that use case.

It's not so easy. The pattern you'd want to try and match or beat moving collectors is arenas, and they're really not trivial to use in C++ (or Rust). The only low-level language that supports them well is Zig. But even then, evolution of the program can often require large architectural changes.

So yes, in principle it's possible to match and perhaps somewhat exceed Java's performance in C++, even in large programs (just as, in principle, it's possible to match and exceed C++'s performance in Assembly), but we don't care about what's possible in principle; we care about what we can achieve with the budget we have. Or put another way, C++ has better performance/effort than Assembly, and Java has better performance/effort than C++ in large programs (perhaps not in all domains, but in important ones). The JVM was designed to (among other things) specifically make it easier to overcome some known performance problems that large C++ programs experience.

> we care about what we can achieve with the budget we have

100% agree on this. This is the last driver for everything else in professional environments.

Related: I think C++ safety being driven by profiles and not the Safe C++ stuff that was proposed violates the economic assumption in so many ways that it was the wrong choice for C++.

Reply on news.ycombinator.com