Develop Reference

Git: Comparing two files in two branches [duplicate]

Is it possible to open a file in a git branch without checking out that branch? How?
Essentially I want to be able to open a file in my github pages branch without switching branches all the time. I don't want to modify it, just want to view it.

This should work:
git show branch:file
Where branch can be any ref (branch, tag, HEAD, ...) and file is the full path of the file. To export it you could use
git show branch:file > exported_file
You should also look at VonC's answers to some related questions:
How to retrieve a single file from specific revision in Git?
How to get just one file from another branch
UPDATE 2015-01-19:
Nowadays you can use relative paths with git show a1b35:./file.txt.

git show somebranch:path/to/your/file
you can also do multiple files and have them concatenated:
git show branchA~10:fileA branchB^^:fileB
You do not have to provide the full path to the file, relative paths are acceptable e.g.:
git show branchA~10:../src/hello.c
If you want to get the file in the local directory (revert just one file) you can checkout:
git checkout somebranch^^^ -- path/to/file

A simple, newbie friendly way for looking into a file:
git gui browser <branch> which lets you explore the contents of any file.
It's also there in the File menu of git gui. Most other -more advanced- GUI wrappers (Qgit, Egit, etc..) offer browsing/opening files as well.

If you're using Emacs, you can type C-x v ~ or M-x vc-revision-other-window to see a different revision of the file you're currently editing (tags, branches and hashes all work).

Add the following to your ~/.gitconfig file
[alias]
cat = "!git show \"$1:$2\" #"
And then try this
git cat BRANCHNAME FILEPATH
Personally I prefer separate parameters without a colon. Why? This choice mirrors the parameters of the checkout command, which I tend to use rather frequently and I find it thus much easier to remember than the bizarro colon-separated parameter of the show command.

Write a batch file that starts a java program

So I have a java project with multiple java files.
I know that is almost straight forward to start a java application using batch file. But that is for a pretty simple java program with a single class.
However I am wondering if it is possible to do that with in a scale of a project that you usually create using eclipse. A large project with multiple packages, classes and multiple java files.
My try was to write a script and apply on the main class as following
set path = C:\Program Files\Java\jdk1.7.0_25\bin
javac -classpath twitter/twitter4j-stream-3.0.5.jar;twitter4j-core-3.0.5.jar" sourcepath="lib/twitter4j-core-4.0.1.jar;lib/twitter4j-core-4.0.1.jar;lib/twitter4j-stream-4.0.1.jar;svm_light_lib Program.java
java Program
However when I start the .bat file it automatically closes.
Any Ideas ?
Thanks in advance

First, never overwrite the environment variable path, not even
temporarily. Append your folder instead: set "path=%path%;%mypath%" or set "path=%mypath%;%path%".
(There exists a particular path command but I'm not sure about right syntax: path=%path%;%mypath% with = assignment or path %path%;%mypath% without it).
Use full path to a program if you know it, e.g. "%mypath%\javac".
For better readability, values for -classpath and -sourcepath options are stored to the environment variables mycpth and mysrcp, respectively. Note and use proper " quotation and no spacing around = to avoid any leading and trailing spaces in all set commands.
pause to see all the javac output. Displays the message Press any key to continue . . .
Next code should be (syntax) error-free. However, success depends (among others) on classpath and sourcepath entries visibility as well...
set "mypath=C:\Program Files\Java\jdk1.7.0_25\bin"
set "path=%path%;%mypath%"
set "mycpth=twitter/twitter4j-stream-3.0.5.jar;twitter4j-core-3.0.5.jar"
set "mysrcp=lib/twitter4j-core-4.0.1.jar;lib/twitter4j-core-4.0.1.jar;lib/twitter4j-stream-4.0.1.jar;svm_light_lib"
"%mypath%\javac" -classpath "%mycpth%" -sourcepath "%mysrcp%" Program.java
pause
java Program

However I am wondering if it is possible to do that with in a scale of a project that you usually create using eclipse. A large project with multiple packages, classes and multiple java files.
Of course it is possible!
In this case, I suspect the problem is that you java command doesn't have a "-cp" argument. The java command is probably failing because it can't find twitter classes ... at runtime.
Remember to include "." on the classpath ... or else java won't find the file that you just compiled.
#JB Nizet's suggestion is also very important advice for finding out what is actually happening.

IntelliJ does not show 'Class' when we right click and select 'New'

We're creating a new project in IntelliJ and must have something wrong because when we right click on a directory, select New and then get the context menu, Java based options are not shown. Currently get things like File, some HTML options, XML options.
We have assumed so far it's something we haven't configured correctly in the Project/Module configuration. The new module we are talking about is part of a multi module project. We created it using a Maven web archetype.
Any help configuring the project nature?
Edit: The answer is basic: 'That moment when you realise somethings not working because you haven't been clicking 'Apply'... :) We had a good laugh at ourselves when we discovered this'

The directory or one of the parent directories must be marked as Source Root (In this case, it appears in blue).
If this is not the case, right click your root source directory -> Mark As -> Source Root.

This can also happen if your package name is invalid.
For example, if your "package" is com.my-company (which is not a valid Java package name due to the dash), IntelliJ will prevent you from creating a Java Class in that package.

you need to mark your directory as source root (right click on the parent directory)
and then compile the plugin (it is important )
as result you will be able to add classes and more

If you open your module settings (F4) you can nominate which paths contain 'source'. Intellij will then mark these directories in blue and allow you to add classes etc.
In a similar fashion you can highlight test directories for unit tests.

Project Structure->Modules->{Your Module}->Sources->{Click the folder named java in src/main}->click the blue button which img is a blue folder,then you should see the right box contains new item(Source Folders).All be done;

I will share another interesting point. If you try to create a package with the reserved keyword then it will be treated as a normal directory and not a package. I was having this issue where I was creating a package named import and it was converting that to a directory.

Another possible solution is that the project name is not acceptable. For example, creating a project with spaces in the name does not block the project creation but the proper sources are not marked and when those are marked manually, I still was unable to create classes. Recreating the project with hyphens (-) instead of spaces corrected the problem for me.

Make sure you are not creating a package name which is same as predefined keywords in java like enum, int, long etc.
In my case I was trying to create a class under "enum" package. As soon as I changed package name to "enums" I was able to create class in it.

Had this issue too. Invalidating Caches/Restart did the trick for me. Please upvote so the the IntelliJ folks take this more seriously. This gives the IDE a terrible UI/UX experience.
https://youtrack.jetbrains.com/issue/IDEA-203100

There is another case where 'Java Class' don't show, maybe some reserved words exist in the package name, for example:
com.liuyong.package.case
com.liuyong.import.package
It's the same reason as #kuporific 's answer: the package name is invalid.

If you just created your project, let IntelliJ finish indexing your project.

You need to mark your java directory as Source Root ,
Right Click on Java directory
Select Mark Directory as option and click on the sub menu option Source Root

Most of the people already gave the answer but this one is just for making someone's life easier.
TL;DR
You must add the test folder as source.
Right click on java directory under test
Mark it as Tests
Add src/test/java in Test Source Folders
Thats it, IntelliJ will consider them as test source.

Eclipse - How to "Change package declaration to ...." across an entire project

I've just imported a large amount of source code into Eclipse and basically the package name is no longer valid (the code has been moved folders). Is there a way to select all the source code in the Package Explorer and hit a hotkey so that all package declarations are correctly resolved for me? I know you can do this with imports by selecting the source and hitting ctl-shift-o, but is also possible for the package declaration?
Update: Refactoring the packages doesn't work as I don't want to change the name or location of the packages, I just need to adjust the package declaration in the Java source code.

If the package declarations are no longer valid, then all such invalid declarations would appear in the Problems view in Eclipse. If you do not see this view, you can open it from Window-> Show View -> Other... -> Problems (under the General tab).
You can filter on problems in the Problems view and correct easily correctable ones, by choosing the Quick fix option in the context menu (available on a right-click). In your case you should see something similar to the screenshot posted below:
Applying the quick fix options is trivial, as long as you know which one is correct - you would either have to change the package declaration in the class, or the location of the class itself. Unfortunately there is no option to fix the issue across multiple units at one go; you will have to apply the quick fix for every problem.
If you want to filter on problems of only this variety, consider configuring the Problems view to show all errors that have the text content "does not match the expected package" in the error text, as demonstrated in the following screenshots:

For this particular problem (which usually comes with auto generated artifact files), I found a neat solution.
So if the issue is that your package declarations is "package abc;" in 200 files, and you want it to be "package com.aa.bb.cc.abc;"
Then in eclipse, Search->File for "package abc;" in required folder or pkg or whole workspace. Don't select Search option but select "Replace" and then put "package com.aa.bb.cc.abc;" when it asks for the replacement after search.
Should do the trick.

Right click on the package, select Refactor > Rename. This will update all source files with the new package name.

I just had the same problem so I wrote a bash script to do it.
function java-package-update {
for path in $(find $1 -type f -name "*.java"); do
D=$(dirname $path);
F=$(basename $path);
P=$(echo $D|tr '/' '.');
if egrep -q '^\s*package\s*' $path; then
sed -i '' '/^\s*package\s*/s/^\(\s*package\s*\)[^;]*\(;.*\)/\1 '$P'\2/' $path;
else
echo >&2 "no package in $path";
fi;
done;
}
The sed command used is the one on OSX. If you're using gnu sed, then you don't need the '' paramater after the -i.
Just paste it in and run it on the directory containing your source. Backup your source first unless you're very brave.
Example:
$ cd /home/me/proj/fred/src
$ ls
com
$ cp -a com com.backup
$ java-package-update com
$ # fingers crossed
$ diff -ru com.backup com
I really should start doing this stuff in a more modern language like perl :)

This should do the trick for you.
Import all your files into the default package first and then drag them into
the new package, JDT will do the refactoring and change the package declarations across the project.

It is an old question, but I ran into the same problem and wrote a very simple bash script. Hope it will help someone.
for i in *.java; do
sed -i 's/.*package com.example.something;.*/package com.example.something_else;/' $i
done
Basically, the script traverses all java files inside a directory, and each occurrence of package com.example.something; replaces with package com.example.something_else;.

ALT+SHIFT+R add underscore at end of package name, hit ENTER twice
ALT+SHIFT+R delete the underscore, ENTER twice
Done if there are few packages.

Java Subclass $

I am new to Java and might be asking a basic question which might sound silly to some.
After I compile my Main Java class most of the subclasses are displayed as $ in the folder. I copy the complied classes and put it on another location to execute. Everytime I make make a change to the main class or one of the sub classes do I need to copy all the associated subclasses? or just copying the changed ones will do?
Thanks.
Nick

Copying the changes will do.
Normally, you would let your IDE (e.g., Netbeans) / build system (e.g., Ant / Maven) do this for you. Alternatively you could create an executable jar-file, leaving you with only one file to copy.

Classnames containing $ are for nested/anonymous classes.
And see this Stackoverflow question.
But that's not the whole point. Quoting OP I copy the complied classes and put it on another location to execute. -- looks like you should automate this task and employ one of traditional Java build tools such as Ant or Maven.

Nick,
Are you referring to nested classes? If so, they will contain "$" in the compiled class file names. Assuming your code changes were only to the parent class, the nested class bytecode should not have changed during the recompilation. It should work to only copy the main .class file. However, it's obviously more of a guarantee to copy the everything.

Is this about subclassing (class Y extends X {}), or nested classes (class Y { class X {} })?
The $ that you mention seems to indicate the latter, in which case you should probably copy everything, but if you are only subclassing then just copying the compiled versions of the files you have changed is probably just fine.