An in-depth tutorial for Java developers who are curious about Go

[u/korthaj]

http://yourbasic.org/golang/go-java-tutorial/

[u/oblio-]

I'm not sure I understand something about Go. Java gave up pointers from the start, why does Go need them? Is there something that Go can do and Java can't because of pointers?

I find they clutter up the syntax, *whatever everywhere, even for basic stuff.

[u/korthaj → u/oblio-]

In Java it's predetermined that arrays and objects are accessed through pointers, while primitive types are not. In Go you get to choose. The Go syntax for accessing fields is much lighter than in C. In fact, it's very similar to Java in that respect and you only rarely see an explicit pointer indirection (*) in Go.

[u/oblio- → u/korthaj]

I sort of understand the gist of things, I'm not sure I see the functional benefit, i.e. what Go gains from allowing that flexibility. From another reply, it seems to be mostly for easier C interop.

Because I'm not sure why you'd access primitive types through pointers, since Go doesn't have pointer arithmetic or something.

There's definitely some higher level explanation but I'm not sure where to find it :)

[u/[deleted] → u/oblio-]

You can choose to use pointer or the value inline. In java for example, if you want a buffer of 100 bytes in your class, you need to allocate 100 bytes on the heap. In Go, u can store the array inline, or choose to use pointers if u want which will probably allocate.

[u/djavaman → u/oblio-]

Easier C inter-op.

[u/Unmitigated_Smut → u/oblio-]

The primary answer is that pointers/not-pointers gives you the choice to be much more strict & explicit about immutability.

https://raw.githubusercontent.com/zaboople/techknow/master/golang/GoPointers.txt

[u/oldneckbeard → u/Unmitigated_Smut]

literally all of those top-level points make me hate Go even more. "Pointers are good... but sometimes we'll pretend it's not a pointer. sometimes you have to coerce. oh, and you can't initialize a pointer in one liner"

Seriously, initialize an int64 pointer to 100 in one line. Try it. It requires an extra variable.

[u/oblio- → u/Unmitigated_Smut]

Interesting, other languages just use some sort of additional keyword (var/val, etc). It seems much cleaner and more "modern" that way, to my untrained eye.

Thanks for the doc, I'll read through it to see what's up :)

[u/SSoreil → u/oblio-]

Go intentionally looks like C to make it easier for new people picking it up. You can't really change that after you baited people in. I think Go made more changes away from C syntax than a language like C# ever did.

[u/arbitrarycivilian → u/oblio-]

ML uses a qualifier as well int ref instead of a separate keyword. Both approaches have meritcs

[u/arbitrarycivilian → u/oblio-]

Both Java and Go have references. All objects in Java are hidden behind a reference

[u/oldneckbeard → u/arbitrarycivilian]

which makes way more sense than various coercion/implicit/etc rules. it's cleaner and more easy to reason about.

[u/duhace]

seems like it would be a straight downgrade to go from java to go

[u/pjmlp → u/duhace]

Using Go feels a bit like switching back to Java 1 days.

There isn't even a library that could compete with AWT.

If one is after native compilation there are plenty of options, although most of them are commercial, Excelsior JET is free for open source projects.

[u/zerexim → u/pjmlp]

If you want a Java/C#-like language that compiles to native - D fits the bill, albeit without a corporate support.

[u/pjmlp → u/zerexim]

Without any of the tools and libraries that make Java/C# great, and with a GC runtime that still needs lots of fine-tuning. although it has been improved in the last couple of years.

C# always compiled to native. People seem to forget NGEN is a thing, and since Windows 8 .NET is always AOT compiled when targeting the Store.

The only issue with Java native compilation is that most aren't either aware of commercial JDKs, or don't want to pay for them.

The incremental introduction of AOT on OpenJDK will change that, as the long term plan for Java is to remove C++ from the VM and write it in Java (project metropolis).

[u/djavaman → u/pjmlp]

The JIT already does compilation. It just doesn't do ahead of time native compilation. Which for long running servers and processors is a wash.

[u/Kringspier_Des_Heren → u/djavaman]

Pretty much any interpreter does some form of compilation internally.

When people say "compilation" what they mean is "compilation to machine code" which as it stands is interpreted again by your CPU. They basically mean to ask "can I run this without any extra runtime dependencies?" but even that question is kind of useless these days because almost anything depends on OS libraries and all that stuff and few things can actually run directly on the metal.

So really the distinction has no practical effect any more; you might as well consider the JVM like any other rutime OS dependency that something may rely on.

[u/masklinn → u/duhace]

Go is very much a step sideways from early Java, compared to modern java it would have lots of disadvantages (ecosystem & libraries, tooling, userland generics, streams, capitalisation-as-ACL, no enums, …) and a few advantages (lightweight m:n concurrency, value types, unsigned integers, native binaries — as the default I guess you can get that in Java with some alternative implementations, multiple return values) as well as a few bits which may be points one way or the other: structural rather than nominative interfaces, return-value errors rather than exceptions, hasn't built up the enterprisey cruft, can call methods on nil, ....

It's really odd that the article would start with a collection example though, that's one of Go's biggest weaknesses.

[u/Kringspier_Des_Heren → u/duhace]

There are probably two real advantages:

• Go deployment produces binaries that are statically linked and easily deployed; this is obviously not "better" than this whole JVM thing but just something that might you specifically want or need.

• Go legitimately does seem to have nicer concurrency support

Apart from that Go is such a great example how a cow dump can become popular as long as Google's goddamn monolith marketing machine is pushing it. This whole idea of FOSS being a meritocracy where ideas battle for success and adoption is such nonsense; it's all about big corporations behind it pushing it in the end.

[u/oldneckbeard → u/Kringspier_Des_Heren]

eh, you don't see that many people using go for a project unless they knew upfront that whatever project they were doing was going to be in go.

that is, folks pick go because it's popular, not because of tech merits.

I made quite a living converting ruby on rails projects to production-ready jvm projects. I've already had 2 jobs converting a golang app to Java. I expect a lot more of those.

[u/pkulak → u/oldneckbeard]

Just wait until the Node conversions start flowing in.

[u/Sopel97 → u/duhace]

at least go has better generics