Ask HN: Why not Java?

52 points by OmegaHN 13 years ago | 109 comments

I am building a web crawler to access data to be processed. All the code is fairly high level, so I am drawn to Python, but there are certain bits of it that require data manipulation that is much easier in a C-like language (arrays are a big part of it).

Java seems to fit this role very well. It is statically typed, object-oriented, and doesn't delve into memory. However, it seems to get a lot of hate (or, at least, dismissal) from many programming communities, so I am asking, why not Java? Why is it so horrible as a systems language above C? Is there any other language that fits this role in a better way?

I am in particular asking this because I have been banging my head against the Python syntax for awhile, but I am trying to expand what languages I can program in.

strlen 13 years ago |

It's perfectly fine to use Java for this kind of software.

The hate against Java comes from using Java for application development: this is largely due to the kinds of applications that are typically written in Java (line of business software) and (this is the most important reason) accidental complexity and low quality of APIs like Spring or J2EE.

Recipe for programming happyness is to use the right tool for the job:

* Python (or Ruby) for web application development, development tools, and "devops" scripting.

* C (or C++) for pieces that need deterministic performance[1], provide a "native" feeling user interface, or require control over memory layout.

Note: performance and efficiency are relative to what your throughput and latency requirements are. Google's crawlers and indexers will remain in C++ for the foreseeable future, but (for example) crawlers for an intranet can get away with being in Java (or Python for that matter).

* Java (or Scala, Haskell, OCaml, Go, Erlang, or one of the many Lisps) for "userland" systems programming. If the majority of the system fits under the last bullet point, use C++.

* Avoid JNI or Swig if you can. Use JSON + REST for cross-language RPC. If you need performance guarantees of a tight binary protocol use Thrift or Protocol Buffers. If you have to use JNI, consider using JNA first.

* No matter what language you use, stick to high quality libraries and tools. For Java, you'll absolutely want to use guava, Guice, and either Netty (or NIO.2 if you are using Java 7) or Jetty + Jersey + Jackson (for REST APIs).

Pick up either emacs and cscope, netbeans, Eclipse, or IntelliJ for navigating a large Java codebase.

All Java build tools suck. Maven sucks less and is the de-facto standard in the open source community. Twitter's "pants" is also worth looking at.

* Don't touch Spring with a 60-foot pole: in the mildest terms it's unequivocal and absolute garbage. Ditto for any other buzzword you may see in a job listing for an "enterprise" Java development job (with 20 years of experience required, naturally).

[1] Java performance can be quite high, but a JIT-ted and garbage collected runtime implies a lack of determinism.

slurgfest 13 years ago | |

This post reflects the conventional wisdom very accurately. It is informative and contains good advice.

However, I also think it is a biased caricature based on "common sense" that isn't all that well founded.

Most of these languages are entirely usable in areas far outside the prescribed areas you have given for them.

If you are working on a few domains like embedded or OS stuff, low-level graphics or signal processing - or you need to interact with a specific system that is pretty language-specific like Rails or iOS - then your options narrow a lot. A few tasks are just a little forced unless your level of comfort is very high (doing 1-minute shell script jobs in C++, for example).

But it would be very hard to overstate the degree of overlap, in 2012. It no longer usually makes sense to write things in ASM for speed, for example...

In the rare situations where your favorite higher-level language is somehow not good enough for a given project, it is rare that you cannot make a mongrel project which drops to another level just where necessary. If your language does not support this then it is broken in a generally important way.

If you are not really ready or willing to fill in gaps and just want to glue existing things together, that changes things slightly - then your primary consideration is not the language but the available libraries.

The major differences between languages are mostly matters of custom and ideology rather than niche suitability.

DVassallo 13 years ago | |

Can you give us some evidence why Spring is "unequivocal and absolute garbage"?

strlen 13 years ago | | |

Well, for starters the whole idea of programming in XML. That and gems such as http://static.springsource.org/spring/docs/2.5.x/api/org/spr... or http://static.springsource.org/spring/docs/2.5.x/api/org/spr...

Of course I can't a priori prove that Spring is garbage, much like I can't a priori prove that it's better to be healthy and rich than to be poor and sick. It is a judgement call, but a judgement call that I believe I'm qualified to make, having worked with a large Spring codebase for 2.5 years.

mbreese 13 years ago | | |

I haven't used it for a few years, but I always found it funny that a project that was supposed to make Java application development easier and more agile than J2EE ended up being just as large, if not larger. Core Spring did a lot for dependency injection, which was a big shift in thought. However, for dependency management, I'd go with something like Guice today.

exelib 13 years ago | | |

Spring was innovative in 2008. Now, Spring is overbloat, buggy (look at request-mapper) and have old, sensless integration to others modules, see spring-data for NoSQL, or try integrate last version of Velocity with last version of Spring.

And additionaly, all, what you can do with Spring, you can do with JEE.

fingerprinter 13 years ago | |

I wish HN had the ability to pin posts. This is great. Absolutely what I was going to write, so naturally I think it is brilliant ;)

The right tool for the job. Java has it's place and it just where strlen said it should be.

swah 13 years ago | | |

I've been highlighting stuff with Diggo these days...

mparlane 13 years ago | | |

Link to the comment as a bookmark.

esschul 13 years ago | |

Rigth tool for the right job is key here. I personally like to add Groovy to the devops list.

exelib 13 years ago | | |

I think groovy is sensless language. You lost all Java benefits like checked exceptions, robust code... what is about debugging? And you is not faster developing with groovy. You developing faster if you ensure quality and not inline filters or other crap. If you like groovy, look at Python.

bkyan 13 years ago | |

What does "userland" mean?

tikhonj 13 years ago | | |

That's what normal applications are referred to as opposed to kernel-level code. So anything user-facing that does not need low-level system access.

mbreese 13 years ago | | |

Code that isn't part of the OS kernel.

http://en.wikipedia.org/wiki/User_space

amirmansour 13 years ago | |

Yes, but you can use Java (or Scala) where C++ was mentioned.

norswap 13 years ago | | |

The rationale for the distinction is given: deterministic performance.

zht 13 years ago | |

Spring is not garbage.

yifanlu 13 years ago | | |

Why is it not garbage?

gojomo 13 years ago |

Nothing's wrong with Java. Commercial and research-quality crawlers of tens of billions of web resources have been written in Java for over a decade. Its threading/concurrency support and extensive well-optimized libraries make it easier for you to make your code fast over large datasets... if you're good at Java. (If you're not, there are plenty of ways to sabotage yourself.)

But, Java's a bit verbose, has gaps in concise support for higher-level constructs, and sometimes the static typing gets in the way. So if you don't find those parts helpful -- some do -- and think your performance targets can be met with other later optimizations/design-choices/selective-reimplementations, stick with whatever more concise language you're good at.

Or, use any of the more concise languages available on the JVM allowing intermixing of the occasional Java facility, like Jython, JRuby, Groovy, Javascript, Scala, Clojure, and others.

(If efficiently handling massive numbers of concurrent net/IO streams is a priority, the recent JVM-based project vert.x may be of interest. I haven't used it for anything but toy tests, but it seems to combine some of the best-practices for maximum JVM IO throughput with a somewhat higher-level-language-agnostic top layer well-suited for servers/proxies/crawlers.)

marbu 13 years ago | |

I agree, java is completelly ok for implementing a crawler. For example the well known mercator crawler was written in java and it's authors stated:

Although our use of Java as an implementation language was somewhat controversial when we be- gan the project, we have not regretted the choice. Java’s combination of features — including threads, garbage collection, objects, and exceptions — made our implementation easier and more elegant. More- over, when run under a high-quality Java runtime, Mercator’s performance compares well to other web crawlers for which performance numbers have been published.

source: [Mercator: A scalable, extensible web crawler (1999)](http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.151.5...)

Derbasti 13 years ago |

In my experience many Java programmers don't really "program" Java. They are more like "expert Eclipse users" and Eclipse happens to output Java. This style of development makes heavy use of wizards and those Eclipse refactoring tools.

This probably is a consequence of the verbosity of Java-the-language, which made heavy tooling support a necessity. And then Eclipse, which provides one of the tightest language integration with Java of any IDE ever.

The sad thing is that this is not really the fault of Java-the-language or Eclipse. It did spawn a whole caste of very mediocre programmers and libraries though, which can make for a very unpleasant culture.

Used correctly, Java can be a great tool, though.

beothorn 13 years ago | |

The verbosity of java allows an IDE like eclipse to exist. I agree that's very hard to program java without a powerful IDE, but there are a lot of things that you can do only with a static typed language and a IDE like eclipse. It's a fair trade. Could you ellaborate on the link between IDE dependency and the spawn a whole caste of very mediocre programmers? (english is not my first language, so sorry if anything I wrote sounds rude)

Derbasti 13 years ago | | |

Sure, I can elaborate.

The idea is that as a programmer, you have to have an intimate understanding of what is going on in order to make the machine do your bidding quickly and correctly.

But that mediocre Eclipse user I caricaturized does not have that understanding. He certainly knows how to get the job done for a certain set of tasks, but he does not know the details of how this is happening. Thus, he creates programs that follow "best practices", "conventions", "design patterns" and lots of automatically created wizard-boilerplate.

That might not be "bad code" mind you, but it almost certainly is not "great code", either. Thus, mediocre. And then these people create libraries that are mediocre and try to use only libraries that they can understand and that are hence mediocre. A culture emerges that is very consistent, but also very mediocre.

slurgfest 13 years ago |

I am puzzled at how arrays are hard to use in Python? I cannot understand how you could be 'banging your head' against Python's array syntax unless you are just new to Python.

If you want to use Java (e.g.: you know it already and don't like learning other things), who cares? Why is this an issue where you have to challenge other people's opinions of Java? Use it if you want to.

rbanffy 13 years ago |

You can always do the speed-critical parts in C and link that from your Python code. Or, if your analysis is something already done, use a library already written in C (such as NumPy).

Another approach could be Jython (or any other JVM language closer to the desired level of abstraction) and Java.

I don't have much love for Java the language. It's not much easier to program than with C, isn't faster and is very verbose. Still, what you are doing looks like a good match for it. And all the respect I don't have for the language, I have for the JVM.

I wouldn't use if for web app development as there are much more productive options around.

samspot 13 years ago | |

I noticed a lot of criticism of Java's verbosity in the comments and I'm a bit curious what people are referring to? I work primarily in Java, but also do quite a bit of Javascript and Perl, and I don't notice Java being especially verbose. Maybe internally I'm giving it a break because it isn't a scripting language? I'm honestly curious to see what you guys think.

orangecat 13 years ago | | |

The two areas that most frequently annoy me are processing collections and (lack of) first-class functions.

Java:

  List<String> firstNames = new ArrayList<String>();
  for(Person p : people) {
    firstNames.add(p.getFirstName());
  }

  addCallback(new Runnable() {
    public void run() {
      doSomething();
    }
  });

Python:

  first_names = [p.first_name for p in people]

  add_callback(do_something)

Scala:

  val firstNames = people.map((p) => p.firstName);

  addCallback(() => doSomething());

The Python and Scala versions do exactly what they say, while the Java code has a bunch of boilerplate that you have to mentally filter out before you can understand what it's doing. And the Scala code is fully typesafe; the compiler infers types rather than making you continually repeat them.

samspot 13 years ago | | |

Curious enough in fact, to do some research. I found an interesting article: http://www.informit.com/articles/article.aspx?p=1824790

I also forgot about file i/o, which I don't do much of in web applications.

rockyj 13 years ago |

Java is good, make no mistakes about it. It offers you find grained control in almost every aspect of programming (e.g. concurrency). However it is the same freedom that allows developers to make mistakes. For example -

One can write concurrent systems in Java without understanding concurrency. Languages like Scala and Clojure will give you some freedom but will also enforce certain design principles which will save you.

Similarly for web development, there are scores of frameworks in the Java world, and you can mess it up easily. Rails / Django on the other hand will provide one good, solid way to do web programming.

Finally, Java is showing it's age. The need to write large files of XML to configure things and the lack of ability to treat functions as objects put developers off. Some things are being addressed by Oracle but will take time.

btilly 13 years ago |

I am curious about what, specifically, you find easier to do in Java syntax than Python syntax.

Seriously, there is a fairly direct translation from any Java you might want to write to completely equivalent Python. Sure, Python offers more complex techniques such as list comprehensions and iterators. But you don't need to use them. You can just write Java-like Python.

mturmon 13 years ago | |

And, the OP says he wants to move away from Python to a C-like language for better arrays? It's a weird reason given that arrays are not that complex a data structure, plus the option of using numpy arrays, which are quite fast and capable.

fusiongyro 13 years ago | |

Interfaces.

pmiller2 13 years ago | | |

Abstract base classes. See http://www.doughellmann.com/PyMOTW/abc/

slurgfest 13 years ago | | |

That is a noun. What is the actual use case?

tsahyt 13 years ago | | |

There's just no need for Interfaces when you have duck-typing at your disposal.

pacala 13 years ago |

> Why is it so horrible as a systems language above C?

* First class functions (interfaces with one method) plus garbage collector eventually encourage a functional programming style, with lots of little objects created on the heap. Alas, the per-object memory overhead of popular Java implementations is horrendous.

* Strong emphasis on using threads for concurrency. Alas, in practice, threads are incredibly large memory hogs.

* Verbosity. While it is possible to write clean composable code in Java, it is also remarkably verbose. After a while, this gets old and people take all shortcuts they can to limit verbosity. Which is a very bad idea. To quote an esteemed colleague, "I never took a shortcut I didn't regretted it later". Can we have our lambdas yet, pretty please?

spartango 13 years ago | |

* If you are using the JVM's generational + concurrent garbage collectors, generally the hoards of little objects disappear without hiccups or leaving much of a footprint.

* My beef with threads for concurrency revolves not around memory footprint (can you substantiate threads as "memory hogs"?), but instead around the necessity to be mindful of resource sharing. Yes, the JDK gives you lots of useful tools in this quest, but it's still not all that difficult to end up with a deadlocked app.

Evbn 13 years ago | |

Java's heavy syntax for anonymous classes and immutables actually discourages functional programming even when that's a strongly desired approach by the programmer.

phao 13 years ago |

There is a hate against Java, also against C#, C++, PHP (which I hate), C, and pretty much any other mainstream language.

Notice, though, that competent people have done great jobs using these languages. So you have some choices. Two of them are: wonder why people bash Java or go do something useful with it. I suggest you do the second.

The key to using programming languages is in trying to use the one which will help you the most, or get in your way the least. Sort of "the right tool for the job". Idk what jobs java is good at. If you found out that it's good for your project, then use it.

Take a look a this article: http://prog21.dadgum.com/143.html

orangecat 13 years ago |

Why is it so horrible as a systems language above C?

It's not "horrible", it just has many slight-to-moderate deficiencies and annoyances that make development more work than it should be.

Is there any other language that fits this role in a better way?

Scala is strictly superior when used as a "better Java". (If you go deep into its functional capabilities you get a different set of tradeoffs). C# is better as a language, but then you're tied to .NET.

Really we'd need to know more details of what you're doing and why you believe Python may not work. Are you concerned about performance, or do you need to do things that Python doesn't have convenient APIs for?

nostromo 13 years ago |

I've written two crawlers in Java and found it quite well-suited.

I think most people on HN who hate Java are talking about creating websites, and for good reason. Back in the bad ol' days, people would use Java frameworks like Struts for web apps, and it was quite painful.

For my latest project I'm using Play Framework for front-end Java, and it's quite delightful.

boyter 13 years ago | |

Agreed. I am in the process of porting a site from PHP to Play and I am loving it.

I am a fan of lots of languages, but recently for anything I am supporting for a long period of time I want static typing to catch massive re-factoring issues. Id rather use C# then Java personally, but Play is an amazing Java framework to use.

harman 13 years ago | |

Play framework is definitely a good Java framework to use. In my current projects I am finding it very useful.

freeslave 13 years ago |

Nothing wrong with using Java and there is something to be said for using the language you are most productive in. But if you are thinking of building a web crawler in Java, I would recommend taking a look at the Heritrix project: https://webarchive.jira.com/wiki/display/Heritrix/Heritrix It's robust, open source and easily extensible. Might be easier to write a custom module for it than to roll your own web crawler.

samspot 13 years ago |

The best reason to use Java is the enormous ecosystem of libraries and resources.

The best reason to AVOID using Java is the huge demand for Java programmers and the low supply. At my job we can barely find applicants with Java so we end up hiring .NET people and converting them.

EnderMB 13 years ago | |

Wow, that's almost entirely the opposite problem I've found in Bristol (UK). There seems to be a lot of people that have stuck with Java after graduating from university and a severe lack of any mid-to-senior level .NET developers.

Out of interest, how do these guys find the switch to Java from C#, assuming they're not VB.NET guys?

beothorn 13 years ago | |

Just curious, where do you live?

samspot 13 years ago | | |

I live in Phoenix, Arizona, and i've heard my old market (Raleigh, NC) is experiencing similar issues.

bbayer 13 years ago |

I personnally dont like Java because of API complexity and this is why ended up with python. I have implemented many crawlers by using Scrapy framework and I believe it speed up development. We have crawled millions of pages without any problem.

Python is very powerful in terms of string manipulation because it has very good language constructs (like slice syntax) which makes development easy. At the beginning it might be a little bit confusing but once you mastered it you really feel power.

Twisted like frameworks also makes good job at this point. It is well-designed, asynchronus and it suits well for multi-tier network applications.

jfb 13 years ago |

It's a lousy language (IMO) with some excellent libraries and very fast compilers. If you're comfortable with the limitations of the language, and you're having trouble with Python, it's worth a shot, I guess.

Mikera 13 years ago |

Java is a great platform to build on - and the sweet spot is definitely for server side applications like this.

You can safely ignore the people who bash Java - they are generally clueless. The Java language is perfectly fine: high performance, statically typed, OOP, relatively simple and maintainable. It may not offer the most concise code and it may not have all the "trendy" language syntax features but guess what - that actually doesn't matter much in the real world (i.e. outside the realm of language designers and fanboys). If saving a few characters of typing is your major concern when choosing a language, you have much bigger problems.

But the real strength in Java is not the language but rather the overall platform - the combination of the JVM (which is an amazing high performance feat of engineering), the library ecosystem (which is the best overall for any language), the tools (great IDEs, Maven, a host of other developer-focused tools), the fact that the OpenJDK itself and most of the libraries are open source and the portability (compiled JVM code is extremely portable, and importantly doesn't need a recompile unlike some other so-called "cross-platform" languages)

So overall you can't really go wrong with choosing Java for server side applications. Although I would also give Clojure or Scala a look - if you are after "powerful" languages then these two are pretty amazing and you still get all the benefits of being on the Java platform.

jvvlimme 13 years ago |

Java is suited and even powers some powerful crawlers like Heritrix (archive.org) and Nutch (Apache foundation).

That being said, it doesn't really matter what language you write your crawler in: its performance will much sooner be influenced by other aspects (network latency, storage, etc) than the language you choose.

So pick the language you're most comfortable with for crawling and offload the data processing to a lower level language that is better sooted for that task.

Tichy 13 years ago |

It's just that Java is very verbose, and actually I found it particularly horrible for data driven applications (by this I mean apps whose behavior is determined by data/config files, not "Big Data" - I have no experience with the latter). For complex data types you always need to create complex class hierarchies. In other languages you could just write

webInfo = {url: "bla.bla", title: "bla die blub", links: ["link1", "link2"]}

Notice that webInfo contains two different types, Strings and Arrays. In Java arrays or hashes you can not easily mix types - you'll end up just putting objects everywhere, then be forced to litter the code with type casts. Or you create the unwieldly class hierarchy. That is my prediction, anyway - I am too lazy to come up with a good example :-(

You can also not simply write something like the hash above. The nearest you can get is if you have created that class hierarchy with suitable constructors, you could instantiate that in one go. At least that is my memory - I have now avoided it for so long that I am not even sure how to instantiate an Array or a Hash with data on the fly anymore.

I think instantiating an array with data goes something like

links = new String[]{"bla", "blub"}, and there is nothing like that for Hashes - you are stuck with

info = new HashMap()<String, Object>;//generics are particularly ugly and annoying

info.put("links", new String[]{"bla", "blub"});

info.put("title", "some stupid web site");

info.put("url", "undisclosed");

And so on - a far cry from the example above. (Note the Java syntax is probably wrong, created from memory - but it is something like that).

Even if you went through the mind numbing work of creating appropriate classes, you'd be stuck with

info = new WebInfo(title, url, new String[]{link1, link2,...});

And that is just for two different types, and notice that there is no way to see what the name of the parameters of the WebInfo constructor actually are from that snippet of code.

title: someTitle

is actually much more readable because you can instantly see that someTitle is supposed to be a title.

Also if you want to use NoSQL, I suspect converting java classes to JSON could be a pita, too.

ljw1001 13 years ago |

There are some good, reasoned comments here. Java suffered through some unfortunate 'best practices' that tarnished it's reputation. Building is uh, suboptimal, as some have pointed out, but if you're working alone just keep it simple and it shouldn't be a problem.

Unless you're building something that needs to be (1) highly dynamic (like a web-based spreadsheet where you don't know the column types til run-time, or (2) true real-time software, you're probably better off using java. Some libraries do suck as others wrote, but it's the volume of good libraries you care about. In any case, I'd argue that in many alternate languages, the code you're writing so quickly doesn't need to be written at all in java, because there's a library for it.

Verboseness is a fact in Java, but a decent IDE shields you from that as well. With Java it takes a little longer to get things done, but (in my experience) you spend less time trying on performance, fixing problems in the underlying tools or language, or just dealing with your own bugs and keeping things running. Since most development is maintenance, you want to optimize for that.

mseepgood 13 years ago |

> Is there any other language that fits this role

Go?

NTH 13 years ago |

My main problem is that it has awful support for functional programming, which I find to be a really helpful way of doing something like a web crawler, where you're essentially describing a computation to parse some input. I would use F#, because it offers powerful functional programming tools, is on .NET / VS 2012 (not sure if that's a pro or con for you), and has type inference (so you get the benefits of static typing without the cost of writing out the types of everything).

You should probably check existing web crawler solutions to see if you can adapt them before rolling your own.

lelele 13 years ago |

Java reputation suffers because of the association of such language with corporate drones.

We may say that with the current crop of languages running on the JVM, Java is a low-level language. It is to the JVM what C is to hardware. You avoid coding in both when you have higher-level languages available which will make you more productive.

But when you want to optimize performance on the JVM for specific chunks of your application - without resorting to JVM bytecode of course - Java is the right choice.

exelib 13 years ago |

Java is good enough for all types of projects. People hate Java because... they can't Java right. Personally, I very like Python and JavaScript and features like multiple inheritance or prototyping, higher-order functions and so on. But Java is better sufficient for projects which more complex as "Hello world", because type safe (robust, compile-time feedback), excelent IDE support and incredibly fast and allow fast development (if you can Java, TDD and so on).

kaolinite 13 years ago | |

There are plenty of reasons other than people being unable to "Java right", though I'm not saying that Java doesn't get plenty of hate out of ignorance.

A good example of when you can't use Java would be embedded projects or projects where you need to squeeze even more performance out of your code. Java is fast but it isn't the fastest.

Feel free to love your language of choice but I'd recommend not letting it get in the way of common sense.

exelib 13 years ago | | |

Java bytecode is very compact and used also in embedded systems. Java can be predictable.

Can you show some benchmarks compare java w/ jit and other languages?

I love another language, but Java is better choice.

dotborg2 13 years ago |

You always can use JS/Python/whatever in your java application as a scripting language.

In such case like web crawler, the main issue with Java is the scalability or rather lack of it. You need to code it yourself, but that's not any different than other languages and platforms.

spullara 13 years ago |

DropWizard is a great way to start Java project.