Modern Java – A Guide to Java 8 • Hacker News Board

Re: Modern Java – A Guide to Java 8

#181

Post by incepted » Tue, Nov 17, 2015, 5:03 AM UTC

norswap wrote: post #180

mabbo wrote: post #92

My Java code has improve dramatically since I started (ab)using Optionals. String foo = Optional.ofNullable(paramater) .filter(...) .map(a -> ...) .map(b -> ...) .orElseGet(() -> ...) .orElse(defaultValue) Between this kind of thing, and similar playing with Streams, some of the ugliest code I work with is suddenly quite clear, coherent, understandable.

Two things. First, why is it better than: String foo; if (parameter != null) { foo = ... ; } else { foo = defaultValue; } or even this, if you express all your transformations as a single expression: String foo = parameter != null ? ... : defaultValue I don't get it. Your way of doing seem awfully more verbose. Please note that I'm not against Optional in general (although they are overplayed in my opinion). Second t…

Actually, your way is awfully more verbose, but you didn't notice it because you ellipsized the verbosity.

If you actually take the time to translate OP's code with your own, you will soon find yourself indented six levels with "if (a != null) { ... if (b != null) { ... if (c != null) {...

You get the idea.

Monads (the type class that Optional belongs to) flatten all this boiler plate with a function called... flatMap! And you don't even need to know about it, all you need to do is chain the calls like OP did:

    Optional.ofNullable(paramater)
                       .filter(...)
                       .map(a -> ...)
                       .map(b -> ...)
                       .orElseGet(() -> ...)
                       .orElse(defaultValue)

without having to check against null every step along the way.

Re: Modern Java – A Guide to Java 8

#182

Post by incepted » Tue, Nov 17, 2015, 5:05 AM UTC

malcolmgreaves wrote: post #160

mabbo wrote: post #92

My Java code has improve dramatically since I started (ab)using Optionals. String foo = Optional.ofNullable(paramater) .filter(...) .map(a -> ...) .map(b -> ...) .orElseGet(() -> ...) .orElse(defaultValue) Between this kind of thing, and similar playing with Streams, some of the ugliest code I work with is suddenly quite clear, coherent, understandable.

Welcome to the world of functional programming =D. I personally (and professionally) suggest moving toward Scala when you feel that itch to dig deeper into FP.

Ugh, no. Skip Scala, which is on the decline and headed fast toward obsolescence, and pick a post-Scala language such as Kotlin or Ceylon.

Re: Modern Java – A Guide to Java 8

#183

Post by incepted » Tue, Nov 17, 2015, 5:06 AM UTC

tajen wrote: post #166

grokys wrote: post #117

Earlier quoted context omitted.

I'm not so up on Java, could someone explain why they chose "->" for lambdas instead of the "=>" that C# and ES6 use, as those languages seem to me like they would be the first place to look for inspiration.

I'm not an expert . C++ uses -> for pointer dereference, e.g. o->p refers to the property "p" of object "o". I would assume C# inherits from C++ and had to define another operator. Java probably followed Scala's notation, which is probably derived from mathematics where ↦ is an application (a function) and ⇒ is a simple logical implication.

Actually Scala uses =>, so Java went the opposite way. Kotlin also uses ->.

Doesn't matter much in the long run, you'll get used to whichever your language favors after just a few days or writing code in it.

Re: Modern Java – A Guide to Java 8

#184

Post by incepted » Tue, Nov 17, 2015, 5:19 AM UTC

malcolmgreaves wrote: post #161

escherize wrote: post #2

I personally jumped right into Clojure on the jvm without much Java experience. I've found it to be awesome. Is there a non-political reason that someone should choose Java over Clojure (or possibly Scala)? Where does Java shine?

IMO Java doesn't shine anywhere. It's statically typed, but lacks support to be flexible. Thus many Java programs rely on reflection at runtime or casting. This negates all of the benefits of static typing, turning the language into a dynamic one. The main choice is then either Clojure or Scala. This comes down to dynamic versus static type checking. With a dynamic language, one is significantly less sure if a progra…

> Scala provides the best support for strong, static typing on the JVM

I'd argue that Ceylon and Kotlin offer most of Scala's advantages with none of its baggage and bloat. And drama.

Re: Modern Java – A Guide to Java 8

#185

Post by mercurial » Tue, Nov 17, 2015, 5:26 AM UTC

bad_user wrote: post #177

pjmlp wrote: post #167

Earlier quoted context omitted.

Programs are written once, read multiple times.

Would be curious to find out what that means, since I see it repeated many times in favor of mainstream and verbose languages, such as Java. I get it to mean somehow that Java is more readable, however in my experience that doesn't make sense, as the IDE can deal with generating the boilerplate, but the IDE cannot help with readability. Not even if you include quick navigation by click, since that has been the purpos…

Eclipse folds the import section, and you can get the type of a value by hovering over it, but apart from that, I'm not sure.

Re: Modern Java – A Guide to Java 8

#186

Post by mercurial » Tue, Nov 17, 2015, 5:30 AM UTC

haxeny1 wrote: post #168

mercurial wrote: post #148

Earlier quoted context omitted.

> Comparable returns an int for what should be a 3-value enum. To be fair, I can think of another functional language starting with "O" guilty of exactly the same thing...

I was about to refute your argument by proposing creating a union type. Here is a relevant reference: https://realworldocaml.org/v1/en/html/functors.html (This idiom is a bit of a historical error. It would be better if compare returned a variant with three cases for less than, greater than, and equal. But it's a well-established idiom at this point, and unlikely to change.) Eiffel is similar to ocaml : http://www.in…

> Does anyone know the advantages of the above signature over the Haskell alternative?

Historical reasons, mostly. The only practical advantage I can imagine is that it's a bit shorter to implement a reverse comparison, since you just multiply by -1.

Re: Modern Java – A Guide to Java 8

#187

Post by Nyetan » Tue, Nov 17, 2015, 6:26 AM UTC

incepted wrote: post #182

malcolmgreaves wrote: post #160

Earlier quoted context omitted.

Welcome to the world of functional programming =D. I personally (and professionally) suggest moving toward Scala when you feel that itch to dig deeper into FP.

Ugh, no. Skip Scala, which is on the decline and headed fast toward obsolescence, and pick a post-Scala language such as Kotlin or Ceylon.

Could you point an interested reader towards some stats :) ? I wanted to pick up Frege for a hobby project some weekend soon and would love to read more about the JVM up-and-comers.

Re: Modern Java – A Guide to Java 8

#188

Post by thelastnode » Tue, Nov 17, 2015, 6:51 AM UTC

neemsky123 wrote: post #100

so... when is this coming to android?

You can use a good number of these today with Retrolambda: https://github.com/orfjackal/retrolambda

Re: Modern Java – A Guide to Java 8

#189

Post by pjmlp » Tue, Nov 17, 2015, 6:59 AM UTC

bad_user wrote: post #177

pjmlp wrote: post #167

Earlier quoted context omitted.

Programs are written once, read multiple times.

Would be curious to find out what that means, since I see it repeated many times in favor of mainstream and verbose languages, such as Java. I get it to mean somehow that Java is more readable, however in my experience that doesn't make sense, as the IDE can deal with generating the boilerplate, but the IDE cannot help with readability. Not even if you include quick navigation by click, since that has been the purpos…

It means that anyone strange to the code is able to pick a pile of printouts and have a ruff understanding of the code.

Which is very hard in languages that are a pile of hieroglyphics.

This is very important in teams of 50+ developers, scattered around countries with high attrition rate, having various skill levels.

Also generating boilerplate is just 1% of what an IDE is capable of.

Re: Modern Java – A Guide to Java 8

#190

Post by lmm » Tue, Nov 17, 2015, 8:04 AM UTC

jvz wrote: post #176

lmm wrote: post #18

Earlier quoted context omitted.

All IME, and as a Scala fan: Clojure has a weakly integrated type system (an inherent disadvantage of optional type systems). At the simplest level this makes silly errors much easier and means you have to write more tests to maintain the same defect rate. The lack of types mean you require extensive use of macros for advanced functionality. IME macros have major maintainability issues in a multi-person codebase. Bot…

> The lack of types mean you require extensive use of macros for advanced functionality. Could you elaborate?

A lot of things that can be implemented natively in scala using its fancy type system would likely be done with macros in clojure. E.g. scala-arm, treelog, dependency injection (not that I use it), database transaction management. Or even just async.