Sedro posted:

No, Java can only close over final variables.

Personally, I try to make all fields/variables/parameters final. I'm curious, does this have any impact on performance?

MEAT TREAT posted:

This is going to sound counter to what you guys want, but learn loving maven and be done with it. If you want to do anything with the Java ecosystem you're going to run into it, and it basically replaces all that setup that the IDE does, so I think it's worthwhile for beginners to learn and use it.

By placing all of your source files in the correct directories maven, will compile and generate a jar file containing the compiled sources. You can use that jar file directly from the command line and not have to deal with all the classpath bullshit. There is no benefit to know how to do that poo poo by hand, it's a huge waste of time and ultimately detracts from what you actually want to learn.

One of the main features of maven is its dependency resolution, but for your baby's first program you probably won't require any dependencies. As you start doing more complex things that aren't part of the standard api you'll want to use them and maven can help.

pigdog posted:

Java IDEs don't necessarily do any of that. Yet if you choose to create a project structure, Ant build files and whatnot, then for projects larger than Hello World it's probably a good idea anyway. A good IDE checks syntax, integrity, imports etc on the fly and lets you fix them semi-automatically, saving you a lot of javac->edit->javac cycles. Going for commandline first is kinda similar to learning to write prose by insisting on using a pencil and paper, as opposed to word processor on a computer.

NotHet posted:

What are the cool kids using these days for an MVC Framework? Struts 2 + Hibernate?
I've been playing around with the Spring + Hibernate and it seems to be pretty nice.

TRex EaterofCars posted:

Or you can just use groovy. It makes xml super simple.

TRex EaterofCars posted:

No need to be a dick; XML in Java is so hairy that writing a small class in Groovy is vastly preferable. Java's going polyglot anyhow, might as well jump on board.

To answer your question, XML is basically a first class citizen in Groovy. Both reading and writing are super simple. I make judicious use of MarkupBuilder and XMLParser myself.

http://groovy.codehaus.org/Processing+XML

Kilson posted:

Your class is called 'homeObj', and your last line is 'homeObj.<method>', which looks like a static call. The last line should say 'homeObject.setLocation...' instead.

Also, class names should start with an upper-case letter in Java. It helps avoid things like this.

DholmbladRU posted:

code:

  <form name="setAsSold"  action="markSold.jsp" method='POST'>
   		<select name="setAsSold">
   		<option value="" name="hSold"></option>
   	<%
    for ( int i = 1; i < h.length; i++ ) {
    	
    	String tmp = h[i].getHome();
    	String tmp2 = h[i].getLocation();
    	
        %>
        
		<option name="hSold" value="<%= i%>">   <%=tmp + " " + tmp2%></option>
		
		<% }%>
		</select>
		<th><input type="submit" value="Mark as sold"/></th>
    </form>
    </body>

When displayed the drop down is populated with two concatinated strings. Howester I am unable to get the "value" of the element I select in the drop down when I submit the form. I am using 'request.getParameterValues("stuff")' on the JSP end to get the value. This worked for other forms when they were text fields.

Tots posted:

Forums upgrade or equivalent for anyone willing to help me complete a java assignment tonight. I don't want someone to do it for me, rather to walk me through the whats and whys in a collab online editor.

TRex EaterofCars posted:

Hibernate is great until it's not. Once you hit that wall you will be loving pissed at it until you invariably rip it out. But that all depends on the scale of your application. If it never grows very big Hibernate is perfectly fine. Personally, I like it for prototyping and that's about it. Using the DDL generator (like you mention) is definitely a plus, it's a very slick little tool.

MyBatis is great if you know SQL well and you don't really plan on being a DB nomad. SQL is a fine language and MyBatis is a good way of making your SQL calls less ad hoc.

ComptimusPrime posted:

I don't use the IDE for source control. I use git proper. And NetBeans does not like the way it handles merging files.

MEAT TREAT posted:

This sounds like stupid dogma to me. You're going to have to backup this claim with some examples.

I am in posted:

I used think chaining mutators was a good idea, but the resulting method call chains are really hard to indent properly and a big pain to step into in a debugger.

1337JiveTurkey posted:

I tried this with a set of builder objects which were covariant on the type of the object that they're building and that type had a deep inheritance hierarchy for historical reasons. I tried chaining for the hell of it and came up with something that started off like this and just got more insane:

code:

interface ChildBuilder<T extends ChildType, B extends ChildBuilder<T, B>> extends ParentBuilder<T, B> {
    B setFoo(String fooString);
}

Thermopyle posted:

Yeah, they can recover. I'll just make something from Exception.

(I don't write Java much, so wasn't sure if there was a good provided exception for this)

Hidden Under a Hat posted:

I need to send software that I've designed and coded to Germany, and I'm wondering if there are any special considerations I need to take to make sure it runs the same on an international computer. My software makes frequent timing control checks based on time-of-day to control devices connected via sockets.

Pie Colony posted:

This isn't really a java question per se but it involves java. For a class project (the class is unrelated to concurrency) I'm implementing an algorithm that I want to be parallelized, but I'm not really an expert on the subject. I know the basics, but am interested in how to implement this in the most efficient way.

The algorithm is something like this (I've implemented a non-parallel version):

-------
There are 100 nodes divided into 4 groups.

At each iteration of the algorithm, the node calculates a direction and a distance to move. The direction can be calculated independently for each node, but the distance depends on the locations of all other nodes in the same group.

After each node has been evaluated, some number of nodes get thrown out of each group and replaced with nodes from the other groups.
-------

So I'm thinking of creating it in a master worker style, where 4 threads calculate the distance and direction, then the master does the switching of the nodes between each group. Would this be a good idea?

Helg56 posted:

stuff

Hanpan posted:

Does Java have any kind of event handling / dispatching ala Actionscript 3? I know it doesn't have delegates so the C# system I was hoping to port over won't work. The only thing I can find on Google is the ActionListener interface, but that seems to be specifically for Swing?

For reference, what I am trying to do is listen for events on a particular object. If I was coding a game, for example, I might want to listen for events for when the player jumps, takes damage or dies so the rest of my game can react accordingly.

Devvo posted:

What's a good book / set of online tutorials for learning Java if you already know how to program?

I'm a college student who knows C, C++ and Python, how to write object oriented programming for the last two, and I've taken a Data Structures class in C++. My curriculum was more mathematics based, so I've never touched Java. I'm not particularly interested in taking a Java class in the other computer science track at my university, mainly because they'll be focusing on beginner stuff, but that could be a possibility.

I'd like to learn Java (or C#, I guess) because it's the dominant language in the Real World, Android app development seems interesting, and I feel weird not knowing it when every other CS grad is fed with it.

pigdog posted:

IDEA is even smarter than Eclipse when it comes to autocompleting and programming aides
http://blog.codeborne.com/2012/03/why-idea-is-better-than-eclipse.html

Honest Thief posted:

I recently received a Java project from a colleague that implemented a class diagram's relations with sets. By that I mean something like A -> B -> C means A will have a Set<B> and B a Set<C>.
I'm wondering if there's a better implementation of it, because when I need to, say, get C from A I need to do 2 chained foreach, and I wonder if that's a good thing to do, since it could grow out of hand.

Honest Thief posted:

etc

for(Participation p : this.participation)
for(Team t : p.team)
for(Player p:t.players)
p.age .....yadda yadda....

etc

fletcher posted:

I was using Eclipse for about 4 years and recently switched to IDEA. I don't think I can go back to eclipse now, everything in IDEA is just way more intuitive.

fletcher posted:

Yeah it has search & replace, tons of refactoring tools, debugging tools, etc. I can't think of anything I used in Eclipse that IDEA (free edition) doesn't have.

Aleksei Vasiliev posted:

How do I adjust a date-time to a future time?

Say I have this date-time object:
May 31 2012 10:54AM UTC

How do I adjust its time portion to something like 10AM but have it go forwards, so I end up with June 1 2012 10:00AM UTC instead of May 31 2012 10:00AM UTC?
I'm really bad at calendar stuff so I have no idea what the hell.

I'm using the ThreeTen alpha builds but I can presumably adapt a JodaTime solution/similar to work with it.

MEAT TREAT posted:

I'd say that Java UI applications are a dead end to begin with.

Mindisgone posted:

Is anyone familiar with google maps api using javascript? I am specifically trying to use the geocoder api and my code is as follows:

fletcher posted:

Finally got a core dump for that JNI issue I was having, some sort of bug in one of the libraries that the native code uses.

Had to do the following on Ubuntu 10.04 to get the core dump: http://chrisjakeway.wordpress.com/2011/12/09/ubuntu-10-04-enable-core-dumps/


On to a new issue! How can I store a java object in memcached that does not implement Serializable?

fletcher posted:

Thanks for the suggestions.

We use protobuf for some other stuff. There are tons of different objects from a 3rd party library that I want to cache so I was hoping to avoid writing/maintaining tons of message definitions, need to investigate this though. It's mostly metadata information from a SOAP API, maybe there is something I can do to cache the underlying XML? I wonder if it's expensive to be parsing all the XML over and over though.

Ranma posted:

Understanding poo poo like that is worth roughly $0. Understanding all that stuff and knowing how to properly structure programs, lead product development, and in general get poo poo done would net you a lot of money as a senior lead.

Thermopyle posted:

I don't work in anything programming related, but out of curiosity, how much could someone make as a Java dev who understands as much as me?

trex eaterofcadrs posted:

In Chicago there's a ton of high profile Java firms and talent is thin, you could get near 100k here if you didn't suck and hung around for 4-5 years.

lamentable dustman posted:

50-60k in Atlanta. 85-110k after 5 years.

Tres Burritos posted:

Easiest way to parse xml? I'm this close to just using regexes.

Lord Of Texas posted:

Yeah, I've considered some variation of Null/Missing Object, i.e. returning this guy when Thing isn't found:

code:

MissingThingBean extends ThingBean{

	@Override
	public ThingCode getThingCode(){
		return new ThingCode("The requested Thing was not found");
	}
}

But that means
1) The client is not forced to check for what instance he has
2) if the client doesn't check for the instance, the MissingThingBean gets propagated up to some other layer that may or may not handle it gracefully.

Optional looks like a solid choice though - thanks for the recommendation!

Lord Of Texas posted:

Maybe I'm misunderstanding, but in that case wouldn't you just not use Optional? An Optional return value means the contract is "This can be empty and you should account for that", but if null is not a valid response, that contract says "This cannot be empty, don't worry about accounting for that".

rhag posted:

I personally believe that the contract should be something like this:
1. If the method returns a collection, then it should never return null. Return an empty collection if there are no things there.
2. If the method returns a single object, it returns null if there are no objects that satisfy the condition (find(id) for example).

The best solution is the one provided by Scala with the Optional support, but in Java an implementation of that would only lead to more verbose code for what otherwise should be a simple check.
The worst solution is throwing a runtime exception (like JPA for createQuery(...).getSingleResult()).

Of course, to any solution there are exception cases, and there could indeed be times where returning new Thing("i don't have any") may be valid and preferred, but i personally think this should not be the normal way of doing things.

Win8 Hetro Experie posted:

Instead of Optional, using one of the NotNull annotations and an IDE with an well-integrated static analysis for them would be better if you can make it work in your organization.

I don't like tweaking the return type or wrapping the value. A variable holding the return value of a method has several properties: formal coming from its type, some that are promised by the name of the variable, informal that are inferred from the method's name. Adding more properties by adding annotations scales easily; changing types much less so.

ManlyWeevil posted:

Sedro posted:

Guava's immutable collections are also very nice for creating defensive copies of collections and especially when working with constant data.

Win8 Hetro Experie posted:

Making things actually immutable is a lot more work than deciding not to mutate things that should be immutable.