Question

I am running a non-english Windows 7 system, and apparently Oracle SQL Developer (version 3.0.04.34, 64-bit) tries to auto-guess my preferred language based on the OS. Is there any way to change the language to english?

I’ve tried the tip found at http://misteratmisis.com/infotech/how-change-oracle-sql-developer-interface-japanese-english, namely adding the VM options

AddVMOption -Duser.language=en
AddVMOption -Duser.country=US

to file ide.conf in directory

/ide/bin

within the SQL Developer installation directory, as suggested, but that didn’t help.

Solution (edited on 13.09.2012):

I decided to try again the solution proposed by Alex K. and this time it worked, namely adding

AddVMOption  -Duser.language=en

to the file sqldeveloper.conf file located in sqldeveloper\bin\ folder. I presume that it did work now but not before, because meanwhile I have changed my UAC (user access control) settings in Windows 7 so that I am administrator by default. What happened before was probably that even though the changes appeared to be there, the configuration file read by the program was another one (shadow copy).

Solution for Mac OS X (added on 26.02.2016):

Edit file at

/Applications/SQLDeveloper.app/Contents/Resources/sqldeveloper/sqldeveloper/bin/sqldeveloper.conf

and add the line

AddVMOption  -Duser.language=en

(Tested with SQL Developer 4.1.3.20)

Answer 1

Try to set user.language and user.country properties in sqldeveloper.conf file located in sqldeveloper\bin folder (%APPDATA%\sqldeveloper\<version>\product.conf for more recent versions) .
Sample for set french language:

IncludeConfFile ../../ide/bin/ide.conf

SetJavaHome D:\jdk1.6.0_25

AddVMOption  -Doracle.ide.util.AddinPolicyUtils.OVERRIDE_FLAG=true

AddVMOption -Dsun.java2d.ddoffscreen=false

AddVMOption -Dwindows.shell.font.languages=
AddVMOption -Duser.language=fr
AddVMOption -Duser.country=FR
AddVMOption  -XX:MaxPermSize=128M

AddVMOption -Doracle.jdbc.mapDateToTimestamp=false  
IncludeConfFile  sqldeveloper-nondebug.conf

To switch off language try to remove its support by editing oracle.translated.locales option in ide.boot file (located in ide\bin folder).
For example, if I want to ‘break’ french language support this option will be:

oracle.translated.locales = de,es,it,ja,ko,pt_BR,zh_CN,zh_TW

The original value was:

oracle.translated.locales = de,fr,es,it,ja,ko,pt_BR,zh_CN,zh_TW

The configuration above (sqldeveloper.conf file) will be wrong after remove french support and the french language does not appear as GUI localization.