Develop Reference

How do you check if two commits differ only in code formatting

I was trying to add java checkstyle to a hugh project and got arounf 7000 errors, I figured formatting the whole project will get rid of 5000 errors.
The problem is that my team refused to review this commit (on git) since it is a hugh change. Is there a way/script to easily figure out if two commits differ only in code formatting and have no logical difference.

You could start by checking the diff with some options to reduce some differences, like
git diff --ignore-all-space --allow-indentation-change --ignore-blank-lines HEAD^
It won't ignore more complex refactorings, but it's arguable that a good chunk of style changes only affect whitespace and indentation.

Solution 1
Check out one revision into one directory, another revision into another. Apply the same formatting to both directories. Doesn't matter what particular formatting you apply, it should be just the same for both directories.
Then compare directories use a diff tool of your choice like Meld, WinMerge, Diffinity. If they show no difference, then really two revisions have no differences except of formatting.
Solution 2
The easier way would be not to compare the revisions, but just format the code: revert the commit, check out the "base line" revision, format the code, commit. Then you will be sure that there are no changes except of formatting.

One solution would be to compare the build results (i.e. compile your project and build the JAR or WAR or other artifacts). If you only change formatting, then the resulting bytecode will be equal to the previous one. So a simple bit-by-bit comparison will tell you if no functionality was broken by the formatting change.
Another solution is to just use whatever automated tests you have and run them. Although i assume by the reaction of your team, that you don't have an extensive test coverage.

Merging an outdated branch with HEAD in CVS (Eclipse)

Basically, we have a branch (call it B, it contains some branch specific code) which needs to be merged with HEAD. The problem we're having is that the branch was created long time ago. Since then, HEAD has been updated many times with lots of new features and many bugs have been fixed. The B branch still has most of the bugs already fixed in HEAD and it lacks some features. So, what needs doing is to take some features of branch B (there are probably about 50 files that contain new functionality - I don't know exactly what these files are) while leaving the rest of HEAD intact.
Currently, the merge tool in Eclipse reports more than 1700 changes, doing automatic merge overwrites code in HEAD with that from the branch (thus, introducing back bugs that have already been fixed). Is there a better way to tackle this instead of going through all the 1700 changes and manually merging them?

If I understand your problem, you want to find out what's changed on the specific branch, and apply those changes to trunk. I think the simplest way to do this is to create a patchfile.
Start by checking out the base and tip of the branch into separate directories. You said that you have a base tag, which puts you ahead of 99% of the people who use CVS. If that's not the case, then you can do a date-based checkout. Finding the correct date will be a pain; the easiest way will be to look at the log for a file that you know wasn't changed on the branch, and track down where that branch appears in the revision history.
Second step is to create a patch file that describes all the changes made on the branch. The instructions here seem complete (I did a Google search for "create a patchile" and looked at the top results).
What you do next depends on how big the patch is, and how much the trunk has changed since the branch was cut. If you feel lucky, the easiest way is to check out the trunk and apply the patch as described in the linked document. You're likely to get at least a few failures, and you need to check each of the changes anyway to verify that it still makes sense.
The alternative is to have three windows open: Window #1 is the patchfile, which will tell you the files that changed and what changed in them. Window #2 is the file on the (tip of) the branch, so you can see what it's currently doing. Window #3 is the file on your trunk. In this approach, you copy code from #2 to #3 where it makes sense, and #1 is just used as a guide to what gets copied.
For what it's worth, while CVS is particularly painful at branching and merging, no VCS is good at merging highly-diverged branches (no matter what Joel says).

Identical Android apps with different package names

I have two Android apps that are identical except for the package name. This question has been asked before, and the recommendation was to refactor the package name as required, but I do not regard this as satisfactory. To my mind putting all the code in a source library would be preferable, but is there a better solution?

Putting the shared code in a Library Project is the recommended approach. See http://developer.android.com/guide/developing/projects/projects-eclipse.html#SettingUpLibraryProject

I take it the question is "How to I build both apps without duplication?" An easy answer: have your build system perform the duplication and package alteration for you. And one way to accomplish this even if you're used to letting Eclipse or ant handle everything in ways opaque to you:
make a temporary copy of your entire repository, with the original building only one of your apps.
make all the changes to the copy that will cause it to build your second app.
create a single .patch that expresses these changes.
have your build system perform step #1, apply the patch from step #3, and then reinvoke itself in the copy. "have your build system" means, write a script, add a target to a makefile (even if you normally avoid makefiles), add a target to ant, extend Eclipse, whatever.

Change Java package name in a SVN branch

I currently have a java library in subversion under package:
com.company.product.foo.*
Unfortunately, I have to refactor this into:
com.othercompany.bar.*
That'd be fine as a one-shot. But this has to be performed only on a specific branch. The problem is then to merge changes from trunk to the branch with totally different names.
The only solution I see would be to create a patch file, run some search & replace and then apply it on the branch.
Is there any better option ?

The first most obvious solution is to not use either company name as the package, but rather a trademarked name, or a neutral domain name that would be used going forward.
If that isn't possible (as in the customer doesn't want the two code bases to be seen as connected) the next most obvious solution is to use a source control system that is more friendly to the concept. Git might have better options, or perforce.
If you have to stick with subversion, then I would have it in source control under a neutral package name and then have the build process that checks out the code, moves it, renames the packages, and compiles, once for each company. Or If your IDE can understand it use a Java pre-processor.
Of course, that last one only works if both customers stay on the same base, but if not then the customer would have its own branch, and the build process could copy the code only as appropriate for the correct branch.

I can't see any really good solutions, but would it be an option to just create subclasses under the new package name?
Then the patches could be applied to the super classes, and the sub classes would never actually contain anything.

A good IDE with refactoring capability will be able to handle this in an instant. Once you make the change, commit it to Subversion. One of its strengths is that it treats directories and files the same way, so you can keep the history as you rename packages.
Sounds like you'd want to create a tag for the original; check out and refactor the trunk; commit the changes. Voila - old and new, with the refactored packages on the trunk where they belong.
Perhaps I'm misunderstanding your question, but I don't think you should make the change directly inside Subversion. Change the code and let Subversion do its job.

Things possible in IntelliJ that aren't possible in Eclipse?

Locked. This question and its answers are locked because the question is off-topic but has historical significance. It is not currently accepting new answers or interactions.
I have heard from people who have switched either way and who swear by the one or the other.
Being a huge Eclipse fan but having not had the time to try out IntelliJ, I am interested in hearing from IntelliJ users who are "ex-Eclipsians" some specific things that you can do with IntelliJ that you can not do with Eclipse.
Note: This is not a subjective question nor at all meant to turn into an IDE holy war. Please downvote any flamebait answers.

CTRL-click works anywhere
CTRL-click that brings you to where clicked object is defined works everywhere - not only in Java classes and variables in Java code, but in Spring configuration (you can click on class name, or property, or bean name), in Hibernate (you can click on property name or class, or included resource), you can navigate within one click from Java class to where it is used as Spring or Hibernate bean; clicking on included JSP or JSTL tag also works, ctrl-click on JavaScript variable or function brings you to the place it is defined or shows a menu if there are more than one place, including other .js files and JS code in HTML or JSP files.
Autocomplete for many languagues
Hibernate
Autocomplete in HSQL expressions, in Hibernate configuration (including class, property and DB column names), in Spring configuration
<property name="propName" ref="<hit CTRL-SPACE>"
and it will show you list of those beans which you can inject into that property.
Java
Very smart autocomplete in Java code:
interface Person {
String getName();
String getAddress();
int getAge();
}
//---
Person p;
String name = p.<CTRL-SHIFT-SPACE>
and it shows you ONLY getName(), getAddress() and toString() (only they are compatible by type) and getName() is first in the list because it has more relevant name. Latest version 8 which is still in EAP has even more smart autocomplete.
interface Country{
}
interface Address {
String getStreetAddress();
String getZipCode();
Country getCountry();
}
interface Person {
String getName();
Address getAddress();
int getAge();
}
//---
Person p;
Country c = p.<CTRL-SHIFT-SPACE>
and it will silently autocomplete it to
Country c = p.getAddress().getCountry();
Javascript
Smart autocomplete in JavaScript.
function Person(name,address) {
this.getName = function() { return name };
this.getAddress = function() { return address };
}
Person.prototype.hello = function() {
return "I'm " + this.getName() + " from " + this.get<CTRL-SPACE>;
}
and it shows ONLY getName() and getAddress(), no matter how may get* methods you have in other JS objects in your project, and ctrl-click on this.getName() brings you to where this one is defined, even if there are some other getName() functions in your project.
HTML
Did I mention autocomplete and ctrl-clicking in paths to files, like <script src="", <img src="", etc?
Autocomplete in HTML tag attributes. Autocomplete in style attribute of HTML tags, both attribute names and values. Autocomplete in class attributes as well.
Type <div class="<CTRL-SPACE> and it will show you list of CSS classes defined in your project. Pick one, ctrl-click on it and you will be redirected to where it is defined.
Easy own language higlighting
Latest version has language injection, so you can declare that you custom JSTL tag usually contains JavaScript and it will highlight JavaScript inside it.
<ui:obfuscateJavaScript>function something(){...}</ui:obfuscateJavaScript>
Indexed search across all project.
You can use Find Usages of any Java class or method and it will find where it is used including not only Java classes but Hibernate, Spring, JSP and other places. Rename Method refactoring renames method not only in Java classes but anywhere including comments (it can not be sure if string in comments is really method name so it will ask). And it will find only your method even if there are methods of another class with same name.
Good source control integration (does SVN support changelists? IDEA support them for every source control), ability to create a patch with your changes so you can send your changes to other team member without committing them.
Improved debugger
When I look at HashMap in debugger's watch window, I see logical view - keys and values, last time I did it in Eclipse it was showing entries with hash and next fields - I'm not really debugging HashMap, I just want to look at it contents.
Spring & Hibernate configuration validation
It validates Spring and Hibernate configuration right when you edit it, so I do not need to restart server to know that I misspelled class name, or added constructor parameter so my Spring cfg is invalid.
Last time I tried, I could not run Eclipse on Windows XP x64.
and it will suggest you person.name or person.address.
Ctrl-click on person.name and it will navigate you to getName() method of Person class.
Type Pattern.compile(""); put \\ there, hit CTRL-SPACE and see helpful hint about what you can put into your regular expression. You can also use language injection here - define your own method that takes string parameter, declare in IntelliLang options dialog that your parameter is regular expression - and it will give you autocomplete there as well. Needless to say it highlights incorrect regular expressions.
Other features
There are few features which I'm not sure are present in Eclipse or not. But at least each member of our team who uses Eclipse, also uses some merging tool to merge local changes with changes from source control, usually WinMerge. I never need it - merging in IDEA is enough for me. By 3 clicks I can see list of file versions in source control, by 3 more clicks I can compare previous versions, or previous and current one and possibly merge.
It allows to to specify that I need all .jars inside WEB-INF\lib folder, without picking each file separately, so when someone commits new .jar into that folder it picks it up automatically.
Mentioned above is probably 10% of what it does. I do not use Maven, Flex, Swing, EJB and a lot of other stuff, so I can not tell how it helps with them. But it does.

There is only one reason I use intellij and not eclipse: Usability
Whether it is debugging, refactoring, auto-completion.. Intellij is much easier to use with consistent key bindings, options available where you look for them etc. Feature-wise, it will be tough for intellij to catch up with Eclipse, as the latter has much more plugins available that intellij, and is easily extensible.

Probably is not a matter of what can/can't be done, but how.
For instance both have editor surrounded with dock panels for project, classpath, output, structure etc. But in Idea when I start to type all these collapse automatically let me focus on the code it self; In eclipse all these panels keep open leaving my editor area very reduced, about 1/5 of the total viewable area. So I have to grab the mouse and click to minimize in those panels. Doing this all day long is a very frustrating experience in eclipse.
The exact opposite thing happens with the view output window. In Idea running a program brings the output window/panel to see the output of the program even if it was perviously minimized. In eclipse I have to grab my mouse again and look for the output tab and click it to view my program output, because the output window/panel is just another one, like all the rest of the windows, but in Idea it is treated in a special way: "If the user want to run his program, is very likely he wants to see the output of that program!" It seems so natural when I write it, but eclipse fails in this basic user interface concept.
Probably there's a shortcut for this in eclipse ( autohide output window while editing and autoshow it when running the program ) , but as some other tens of features the shortcut must be hunted in forums, online help etc while in Idea is a little bit more "natural".
This can be repeated for almost all the features both have, autocomplete, word wrap, quick documentation view, everything. I think the user experience is far more pleasant in Idea than in eclipse. Then the motto comes true "Develop with pleasure"
Eclipse handles faster larger projects ( +300 jars and +4000 classes ) and I think IntelliJ Idea 8 is working on this.
All this of course is subjective. How can we measure user experience?

Idea 8.0 has the lovely ctrl+shift+space x 2 that does the following autocomplete:
City city = customer.<ctrl-shift-space twice>
resolves to
City city = customer.getAddress().getCity();
through any number of levels of getters/setters.

Don't forget "compare with clipboard".
Something that I use all the time in IntelliJ and which has no equivalent in Eclipse.

My favorite shortcut in IntelliJ that has no equivalent in Eclipse (that I've found) is called 'Go to symbol'. CTRL-ALT-SHIFT-N lets you start typing and glob up classes, method names, variable names, etc, from the entire project.

I tried to switch to IntelliJ because of the new Android Studio. But I'm very disappointed now. I'm using Eclipse with the Code Recommanders Plugin. Here is a simple example why Eclipse is so awesome:
I want to create a new SimpleTimeZone. SimpleTimeZone has no Constructor with zero arguments.
Ctrl + Space in Eclipse
Ctrl + Space in IntelliJ
In IntelliJ I get no informations what kind of constructors SimpleTimeZone has.
After Enter in Eclipse
I get the previously selected constructor filled with predefined variable names. And I can see the type of every argument. With Code Recommanders Eclipse guesses the right constructor by the previously defined variable types in the current scope and fills the constructor with these vars.
After Enter in IntelliJ nothing happens. I get an empty constructor. I have to press Ctrl + P to see the expected arguments.

If you have the cursor on a method then CTRL+SHIFT+I will popup the method implementation. If the method is an interface method, then you can use up- and down- arrows to cycle through the implementations:
Map<String, Integer> m = ...
m.contains|Key("Wibble");
Where | is (for example) where your cursor is.

IntelliJ has some pretty advanced code inspections (comparable but different to FindBugs).
Although I seriously miss a FindBugs plugin when using IntelliJ (The Eclipse/FindBugs integration is pretty cool).
Here is an official list of CodeInspections supported by IntelliJ
EDIT: Finally, there is a findbugs-plugin for IntelliJ. It is still a bit beta but the combination of Code Inspections and FindBugs is just awesome!

Far, far, far more refactorings.

One thing I use regularly is setting a breakpoint, but then controlling what it does. (At my last job, most everyone else used Eclipse... I remember being surprised that no one could find how to do this in Eclipse.)
For example, can have the breakpoint not actually stop, but just log a message to the console. Which means, I don't have to litter my code with "System.out.println(...)" and then recompile.

There are many things that idea solves in a much simpler way, or there's no equivalent:
Autocomplete actions: Doing ctrl+shift+a you can call any idea action from the keyboard without remembering its key combination... Think about gnome-do or launchy in windows, and you've got the idea! Also, this feature supports CamelCasing abbreviations ;)
Shelf: Lets you keep easily some pieces of code apart, and then review them through the diff viewer.
Local history: It's far better managed, and simpler.
SVN annotations and history: simpler to inspect, and also you can easily see the history only for such a part of a whole source file.
Autocomplete everywhere, such as the evaluate expression and breakpoint condition windows.
Maven integration... much, much simpler, and well integrated.
Refactors much closer to the hand, such as loops insertion, wrapping/casting, renaming, and add variables.
Find much powerful and well organized. Even in big projects
Much stable to work with several branches of a big project at the same time (as a former bugfixer of 1.5Gb by branch sources, and the need to working in them simultaneously, idea shown its rock-solid capabilities)
Cleaner and simpler interface...
And, simpler to use only with the keyboard, letting apart the need of using the mouse for lots of simple taks, saving you time and giving you more focus on the code... where it matters!
And now, being opensource... the Idea user base will grow exponentially.

Structural search and replace.
For example, search for something like:
System.out.println($string$ + $expr$);
Where $string$ is a literal, and $expr$ is an expression of type my.package.and.Class, and then replace with:
$expr$.inspect($string$);

My timing may be a little off in terms of this thread, but I just had to respond.
I am a huge eclipse fan -- using it since it's first appearance. A friend told me then (10+ years ago) that it would be a player. He was right.
However! I have just started using IntelliJ and if you haven't seen or used changelists -- you are missing out on programming heaven.
The ability to track my changed files (on my development branch ala clearcase) was something I was looking for in a plugin for eclipse. Intellij tracks all of your changes for a single commit, extremely easy. You can isolate changed files with custom lists. I use that for configuration files that must be unique locally, but are constantly flagged when I sync or compare against the repository -- listing them under a changelist, I can monitor them, but neatly tuck them away so I can focus on the real additions I am making.
Also, there's a Commit Log plugin that outputs a text of all changes for those SCCS that aren't integrated with your bug tracking software. Pasting the log into a ticket's work history captures the files, their version, date/time, and the branch/tags. It's cool as hell.
All of this could be supported via plugins (or future enhancements) in eclipse, I wager; yet, Intellij makes this a breeze.
Finally, I am really excited about the mainstream love for this product -- the keystrokes, so it's painful, but fun.

The IntelliJ debugger has a very handy feature called "Evaluate Expression", that is by far better than eclipses pendant. It has full code-completion and i concider it to be generally "more useful".

Well, for me it's a thousand tiny things. Some of the macros, the GUI layout in general in Eclipse I find awful. I can't open multiple projects in different windows in Eclipse. I can open multiple projects, but then it's view based system swaps a bunch of things around on me when I switch files. IntelliJ's code inspections seem better. Its popup helpers to fix common issues is nice. Lots of simple usability things like the side bar where I can hover over a hot spot and it'll tell me every implementing subclass of a method or the method I'm implementing and from where.
Whenever I've had to use, or watch someone use, Eclipse it seems like they can do most of the things I can do in IntelliJ, but it takes them longer and it's clunkier.

Introduce variable. (Ctrl+Alt+V on Windows, Cmd+Alt+V on OSX)
Lets say you call a method, service.listAllPersons()
Hit Ctrl+Alt+V and Enter, and variable for return value from method call is inserted:
List<Person> list = service.listAllPersons();
Saves you typing, and you don't have to check the return type of the method you are calling. Especially useful when using generics, e.g.
new ArrayList<String>()
[introduce variable]
ArrayList<String> stringArrayList = new ArrayList<String>();
(of course you can easily change the name of the variable before hitting Enter)

IntelliJ has intellisense and refactoring support from code into jspx documents.

For me, it's IDEA's maven support, especially in version 9 is second to none. The on-the-fly synchronizing of the project to the maven model is just fantastic and makes development pleasant.

Intellij has a far superior SVN plug-in than either Subversive or Subclipse and it works! The amount of time we've wasted merging source files using Eclipse doesn't bear thinking about. This isn't an issue with IntelliJ because the plugin helps you much more.
Also the Subclipse plugin is unreliable - we regularly have instances where the plugin doesn't think there has been any code checked in to SVN by other developers, but there has - the CI server has processed them!

VIM Emulator. This plugin provides nearly complete vi/vim/gvim emulation while editing files in IDEA.
The following functionality is supported:
Motion keys
Deletion/Changing
Insert mode commands
Marks
Registers
VIM undo/redo
Visual mode commands
Some Ex commands
Some :set options
Full VIM regular expressions for search and search/replace
Macros
Diagraphs
Command line history
Search history
Jumplists
VIM help
some comments about this plugin from http://plugins.jetbrains.net/plugin/?id=164
I can't see ever going back to any other ide because of this plugin..
Best of both worlds... Awesome!.
that's what i was lacking in all IDEs.

One of the good points in my opinion is the Dependency Structure Matrix:
http://www.jetbrains.com/idea/features/dependency_analysis.html#link0
There's a good introduction to DSM usage and benefits in Lattix' website (a standalone product):
http://www.lattix.com/files/dl/slides/s.php?directory=4tour

A few other things:
propagate parameters/exceptions when
changing method signature, very
handy for updating methods deep
inside the call stack
SQL code validation in the strings passed as arguments to jdbc calls
(and the whole newly bundled
language injection stuff)
implemented in/overwritten in icons for interfaces & classes (and their methods) and
the smart implementation navigation
(Ctrl+Alt+Click or Ctrl+Alt+B)
linking between the EJB 2.1 interfaces and bean classes
(including refactoring support); old
one, but still immensely valuable
when working on older projects

Two things that IntelliJ does that Eclipse doesn't that are very valuable to me:
Method separators: those faint gray lines between methods make code much more readable
Text anti-aliasing: makes code look so nice in the IDE

One very useful feature is the ability to partially build a Maven reactor project so that only the parts you need are included.
To make this a little clearer, consider the case of a collection of WAR files with a lot of common resources (e.g. JavaScript, Spring config files etc) being shared between them using the overlay technique. If you are working on some web page (running in Jetty) and want to change some of the overlay code that is held in a separate module then you'd normally expect to have to stop Jetty, run the Maven build, start Jetty again and continue. This is the case with Eclipse and just about every other IDE I've worked with. Not so in IntelliJ. Using the project settings you can define which facet of which module you would like to be included in a background build. Consequently you end up with a process that appears seamless. You make a change to pretty much any code in the project and instantly it is available after you refresh the browser.
Very neat, and very fast.
I couldn't imagine coding a front end in something like YUI backing onto DWR/SpringMVC without it.

Preamble to my answer: My use of Eclipse is limited. We needed a Java IDE to work on both Windows and Mac and the Mac port slowed down day by day. This was years ago and I'm sure it's OK now. But that is what got us to switch to IntelliJ and we've been happy with it.
Now for my answer: One big difference I haven't seen mentioned yet is that tech support is better with IntelliJ/Jet Brains. We send an e-mail to JetBrains and get a definitive answer back in less than an hour. Looking for answers to Eclipse problems results in the usual, "You stupid idiot" answers (usually a small number of the replies) along with the much larger number of insightful, helpful replies. But it takes some sorting through to get the real answer.

Something which I use in IntelliJ all the time is refactoring as I type. I have re-written classes from a printout (originally written in eclipse) using both IDEs and I used about 40% less key strokes/mouse clicks to write the same classes in IntelliJ than eclipse.
I wouldn't want to use Eclipse until they support as much refactoring with incomplete pieces of code.
Here is a longer list of features in IntelliJ 8.0/8.1 [http://www.jetbrains.com/idea/features/index.html]

There is one thing that IntelliJ does much much better than Eclipse and that is empty your pockets!
I do however prefer using it and one big advantage it has over Eclipce is the way it synchronises with the file system, for big projects and slow computers (yes in work environments the PC's are a lot slower than our ones at home) Eclipse seems to struggle where IntelliJ seems to be quicker albeit with a slower initial indexing time.
IntelliJ Community edition obviously makes using it free but you soon want those extra refactoring and nice little goodies not included in the CC edition.
In my opinion, its generally a better user experience but whether its worth the cost is a question for each developer to answer themselves.
But lets be grateful we have up to three great IDEs for Java right now with NetBeans getting better all the time.

Data flow analysis : inter-procedural backward flow analysis and forward flow analysis, as described here. My experiences are based on Community Edition, which does data flow analysis fairly well. It has failed (refused to do anything) in few cases when code is very complex.

First of all I love intellij. There are at least a hundred features it has that eclipse lack. I'm talking magnitudes better in reliability and intelligence that no hyperbole can describe when it comes to refactoring, renaming, moving and others which have already been mentioned.
BUT, there is one thing that intellij does not allow which eclipse does. It does not allow running multiple projects at once under the same vm.
When you have separate projects for the front, middle, core, agents..etc, where they all have to interact with each other, you can not quickly modify and debug at the same time, afaik. The only way I current cope with this is to use ant scripts to deploy and update jars in dependent projects, or use maven.
Eclipse allows multiple projects to be debugged under one ide vm instance.