How to read 'List separator' from OS in Java?

How to read 'List separator' from OS in Java?

I am writing a CSV exporter in Java that should respect the user's custom settings, especially the "List separator" to use as a delimiter.

In Windows, one can set this List separator in

Control Panel -> Regional and Language Options -> Regional Options -> Customize  

I don't know about the other operating systems, but I'm pretty sure that you can change that on other OSes, too.

What is the best way to get this custom setting from the OS into Java? I am in an Eclipse RCP environment, so I might use RCP-related solutions if there is something available.

Answer by darko.topolsek for How to read 'List separator' from OS in Java?

For windows it's stored in the registry at:

"HKEY_CURRENT_USER\\Control Panel\\International"  

so you can use something like this

private void setDelimiterProperties(String delimiter) {      Properties p = new Properties();      String key = "HKEY_CURRENT_USER\\Control Panel\\International\\sList";      p.setProperty(key, delimiter);  }  

Answer by ninesided for How to read 'List separator' from OS in Java?

Without resorting to a platform specific solution I think that the best approach to take is going to be to allow users to specify their preference of list separator within your own application. Either in a preferences panel, a dialog box on export or via an optional command line argument.

Answer by Jonik for How to read 'List separator' from OS in Java?

From comments of this answer:

Reading the OS-specific setting is a need I have to meet.

So what if OSs other than Windows don't have such a setting?

I suggest you read it from registry on Windows (as alluded here): Read/write to Windows Registry using Java. On other platforms just use a good default, and perhaps, at least on Unix, also support configuring it via a custom environment variable (which you document well): How can my java code read OS environment variables?.

My gut feeling that OSs universally do not have a (system-wide or user-specific) "List separator" setting may be wrong, of course, but I doubt that.

Answer by PhiLho for How to read 'List separator' from OS in Java?

Out of curiosity, I searched a bit the topic, and indeed Java seems to have not such notion out of the box.

The Locales Demo gives a fairly complete listing of locale settings and there is no list separator there.

I saw a forum question referring to sun.text.resources package, which is private and deprecated. You won't find much other references to this package, looks like it lives in jre/lib/ext/localedata.jar although my recent copy of this one lists mostly Asian locales.

The above advices are sound, or you might research and use a private list per locale. I would look perhaps at IBM's ICU library (C language I think) which seems to have a fairly big list of locale settings. According to a remark, ICU itself gets its information from a an ISO standard, which should be researched as primary information provider.

Answer by romeok for How to read 'List separator' from OS in Java?

In addition to providing your own option to the user in your application you could try to guess what the list separator is.

I had a look at some locales in Windows and saw that the list separator is either ";" or ",". I've heard there is another character in some obscure locale, but have not seen it myself. So if you can make your code to handle both ";" and "," as list separators then you will probably cover majority of cases.

Also, it looks like when "," is used as a decimal separator, then "," is never used as a list separator. I guess this is otherwise numbers will be impossible to distinguish in a list: 1,2,3,4 could be 1.2, 3.4 or 1, 2.3 In these cases ";" is used as a list separator. Unfortunately the reverse is not true. Arabic has "." as a decimal symbol and ";" as a list separator.

So I think the rule that can be reasonably safely followed is:

if (decimalSeparator == ',') then listSeparator = ';' else if (decimalSeparator == '.') then listSeparator = new char[] {';', ','}

Answer by ahlexander for How to read 'List separator' from OS in Java?

I faced the same problem and also found out that the only proper solution is to provide a way to the user to specify the "delimiter of choice".

However, if that is not possible, as it was in my case, the closest I could get to cross-platfrom, cross-locale support is the following:

• guess the separators you need to use using DecimalFormatSymbols
• add a line at the beginning of the CSV containing, for example "sep=," (without quotes), this should specify the list separator you've just guessed

This will, at least in most cases (the cases I have tested), force Excel to use that delimiter, even if you "guessed wrong" and will provide at least a little bit more compatibility.

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