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Comment by zachrip | Hacker News Reader

Why do they obfuscate if they're just going to provide the mappings?

Proguard can also apply optimizations while it obfuscates. I think a good JVM will eventually do most of them itself, but it can help code size and warm-up. I'm guessing as JVMs get better and everyone is less sensitive to file sizes, this matters less and less.

And there's no way to do only the optimisation part? Surely you could optimise without messing up class and method names..?

One of the biggest optimizations it offers is shrinking the size of the classes by obfuscating the names. If you're obfuscating the names anyway, there's no reason that the names have to be the same length.

"hn$z" is a heck of a lot smaller than "tld.organization.product.domain.concern.ClassName"

Yeah in some ways the obfuscation and mappings are similar to minification and sourcemaps in javascript.

And minification in JavaScript only reduces the amount of bytes that has to be sent over the wire, it doesn't improve runtime performance.

According to the v8 devs it also can increase parsing performance

> Our scanner can only do so much however. As a developer you can further improve parsing performance by increasing the information density of your programs. The easiest way to do so is by minifying your source code, stripping out unnecessary whitespace, and to avoid non-ASCII identifiers where possible.

https://v8.dev/blog/scanner

Sure, but that's also just in the category improving loading a bit. It doesn't have anything to do with runtime performance.

So we're not talking about runtime performance, but some minor improvement in loading times? I assume that once the JVM has read the bytecode, it has its own efficient in-memory structures to track references to classes rather than using a hash map with fully qualified names as keys

The names need to be stored somewhere because they are exposed to the program that way

They have to be stored somewhere, but they don't have to be what the JVM uses when it e.g performs a function call at runtime. Just having the names in memory doesn't slow down program execution.

At runtime this is going to be a branch instruction yes

Proguard was heavily influenced by the needs of early Android devices, where memory was at a real premium. Reducing the size of static tables of strings is a worthwhile optimisation in that environment

Okay but we're talking about Minecraft on desktops and laptops, where the relevant optimizations would be runtime performance optimizations, no?

Probably, but proguard tends to bundle the whole lot together

Even a hash map with fully qualified names as keys wouldn't be so bad because Stirng is immutable in Java, so the hash code can be cached on the object.

Well, maybe that's why they're not obfuscating anymore.

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