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run java jar file on HP-UX as UNIX as "os.name"

I need to execute a jar file on HP-UX that I am not supposed to modify.
I unpacked it using jd-gui and found out that I am failing cause in java there is a condition to check the os, leading to different directions for win, macos, freebds, openbds, gnu and so on.
I am quite sure everything would work if I would be able to make my unix command line reply freebds or openbds to the java call
System.getProperty("os.name")
once executed from a jar file like:
java -jar myjar.jar
is there a way to achieve this? some kind of compatibility mode or a way to preset that parameter.

You can use the -D switch to specify system properties. In my experiment this (unexpectedly) even worked with pre-defined ones like os.name. Therefore this should work:
java -Dos.name=linux -jar myjar.jar

UTF-8 characters in a path to a jarfile

I have a folder with Unicode(UTF-8) symbols in its name, for example, Я_Папка, and the folder contains foo.jar.
Now I need to execute the foo.jar:
chcp 65001
Active code page: 65001
C:\>java -Dsun.jnu.encode=UTF-8 -jar C:\Я_Папка\foo.jar
Error: Unable to access jarfile C:\Я_Папка\foo.jar
-Dsun.jnu.encode=UTF-8 switch tells java to use UTF-8 encoding for the platform string.
-Dfile.encode=UTF-8 switch can't help - it works only with the contents of files rather than the command line
My question here - how to make -jar switch understand UTF-8 encoding?

Java doesn't support Unicode (UTF-8) for platform string on Windows by design. You can only use code page set in the System locale.

If you're not on Russian locale you should probably change "system locale" setting. I've had same problem, see the detailed answer.

ant: warning: unmappable character for encoding UTF8

I have seen numerous of questions like mine but they don't answer my question because I'm using ant and I'm not using eclipse. I run this code: ant clean dist and it tells me numerous times that warning: unmappable character for encoding UTF8.
I see on the Java command that there is a -encoding option, but that doesn't help me cuz I'm using the ant.
I'm on Linux and I'm trying to run the developer version of Sentrick; I haven't made no modifications to anything, I just downloaded it and followed all their instructions and it ain't makes no difference. I emailed the developper and they told me it was this problem but I suspect that it is actually something that gotta do with this error at the end:
BUILD FAILED
/home/daniel/sentricksrc/sentrick/build.xml:22: The following error occurred while executing this line:
/home/daniel/sentricksrc/sentrick/ant/common-targets.xml:83: Test de.denkselbst.sentrick.tokeniser.components.DetectedAbbreviationAnnotatorTest failed
I'm not sure what I'm gonna do now because I really need for it to work

Try to change file encoding of your source files and set the Default Java File Encoding to UTF-8 also.
For Ant:
add -Dfile.encoding=UTF8 to your ANT_OPTS environment variable
Setting the Default Java File Encoding to UTF-8:
export JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF8
Or you can start up java with an argument -Dfile.encoding=UTF8

The problem is not eclipse or ant. The problem is that you have a build file with special characters in it. Like smart quotes or m-dashes from MS Word. Anyway, you have characters in your XML file that are not part of the UTF-8 character set. So you should fix your XML to remove those invalid characters and replace them with similar looking but valid UTF-8 versions. Look for special characters like &#64 © — ® etc. and replace them with the (c) or whatever is useful to you.
BTW, the bad character is in common-targets.xml at line 83

Changing encoding to Cp 1252 worked for my project with same error. I tried changing eclipse properties several times but it did not help me in any way. I added encoding property to my pom.xml file and the error gone. http://ctrlaltsolve.blogspot.in/2015/11/encoding-properties-in-maven.html

Java source file encoding with Chinese character

I import a Java project from Windows platform to Ubuntu.
My Ubuntu is 10.10, Gnome environment: My LANGUAGE is set to en_US:en
My terminal's character encoding is: Unicode (UTF-8)
My IDE is eclipse and text file encoding is: GBK.
In source file, there are some Chinese constant character.
The project build successful on Windows with ant,
but on Ubuntu, I get compile error:
illegal character: \65533
I don't want to use \uxxxx format as the file is already there,
And I've tried the -encoding option for javac, but still can't compile.

I think the problem lies not with Ubuntu, Ubuntu's console, Javac or Eclipse but with the way you transfer the file from windows to Ubuntu. You have to store it as utf-8 before you copy it to Ubuntu otherwise the codepoint-information that is set in your Windows your locale is already lost.

Did you specify the encoding option of the <javac> task in your build.xml?
It should look like this:
<javac encoding="GBK" ...>
If you haven't specified it, then on Windows it will use the platform default encoding (which is GBK in your setup) and on Linux it will use the platform default encoding (which is UTF-8 in your setup).
Since you want the build to work on both platforms (preferably without changing the configuration of either platform), you need to specify the encoding when you compile.

You need to convert you source codes from you windows codepage to UTF-8. Use iconv for this.

How to force a jar to use(or the jvm that jar runs in) utf-8 instead of the system's default encoding

My Windows's default encoding is GBK, and my Eclipse is totally utf-8 encoded.
So an application which runs well in my Eclipse, crashes because the words become unreadable when exported as a jar file;
I have to write the following line in a .bat file to run the application
start java -Dfile.encoding=utf-8 -jar xxx.jar
Now my question is that can I write something in the source code to set the application uses(or the jvm runs in) utf-8 instead of the system's default encoding.

When you open a file for reading, you need to explicitly specify the encoding you want to use for reading the file:
Reader r = new InputStreamReader(new FileInputStream("myfile"), StandardCharsets.UTF_8);
Then the value of the default platform encoding (which you can change using -Dfile.encoding) no longer matters.
Note:
I would normally recommend to always specify the encoding explicitly for any operation that depends on the standard locale, such as character I/O. Many Java API methods default to the platform encoding, which I consider a bad design, because often the platform encoding is not the right one, plus it may suddenly change (if the user e.g. switches OS locale), breaking your app.
So just always say which encoding you want.
There are some cases where the platform encoding is the right one (such as when opening a file the user just created for you), but they are fairly rare.
Note 2:
java.nio.charset.StandardCharsets was introduced in Java 1.7. For older Java versions, you need to specify the input encoding as a String (ugh). The list of possible encodings depends on the JVM, but every JVM is guaranteed to at least have:
US-ASCII, ISO-8859-1,UTF-8,UTF-16BE,UTF-16LE,UTF-16.

There's another way.
If you are sure how you like to encode the input and output, you can save the settings before you compile your jar file.
Here is a example for NetBeans.
Go To Project >> Properties >> Run >> VM Options and type -Dfile. encoding=UTF-8
After that, everything is encoded in UTF-8 every time the Java VM is started.
(I think Eclipse offers the same possibility. If not, just google to VM Options.)