Java: ExceptionInInitializerError caused by NullPointerException when constructing a Locale object

Question

I'm working on localization for a program I've written with a couple other guys. Most of the strings now load in the appropriate language from an ini file. I'm trying to do the same with the format of currency in the program. However, I'm getting a runtime exception as soon as I attempt to launch the application.

I'm using the Locale object as a parameter to a few NumberFormat.getCurrencyInstance()'s, like so:

private static final NumberFormat decf;
static 
{
    decf = NumberFormat.getCurrencyInstance(Lang.cLocale);
    decf.setRoundingMode(RoundingMode.HALF_UP);
}

Lang is the class which contains all the localization stuff. The code the IDE complains about at attempted runtime is public static Locale cLocale = new Locale(GUI.DB_info[19],GUI.DB_info[20]);

GUI is the class the GUI is contained in, and where we decided to construct the DB_info array (which itself just contains information loaded from a remote database in another class). DB_info[19] is the language code (es right now) and DB_info[20] is the country code (US). The array elements are being properly filled-- or were, I can't get far enough into the program to tell right now; but nothing has changed with the code for filling DB_info.

The full exception is as follows:

Exception in thread "main" java.lang.ExceptionInInitializerError
at greetingCard.GUI.<clinit>(GUI.java:118)
Caused by: java.lang.NullPointerException
at java.util.Locale.<init>(Unknown Source)
at java.util.Locale.<init>(Unknown Source)
at greetingCard.Lang.<clinit>(Lang.java:13)
... 1 more

The line in GUI referenced is: static String welcome = Lang.L_WELCOME + ", " + empName;, and Lang.java basically looks like this:

// Set locale for currency display
public static Locale cLocale = new Locale(GUI.DB_info[19],GUI.DB_info[20]); // language, country

// Employee specific strings
public static String L_AMT_REMAIN = "";
public static String L_AMT_TEND = "";
public static String L_APPROVED = "";
public static String L_ARE_YOU_SURE = "";
[...]

public static void Main(String emp_lang)
{
    String header = "";

    if (emp_lang.equals("ENG"))
    {
        header = "ENG";
    }
    else if (emp_lang.equals("SPA"))
    {
        header = "SPA";
    }
    else if (emp_lang.equals("FRE"))
    {
        header = "FRE";
    }
    else if (emp_lang.equals("GER"))
    {
        header = "GER";
    }
    else
    {
        header = "ENG";
    }

    try 
    {
        Ini ini = new Ini(new File("C:/lang.ini"));

        L_AMT_REMAIN = ini.get(header, "L_AMT_REMAIN");
        L_AMT_TEND = ini.get(header, "L_AMT_TEND");
        L_APPROVED = ini.get(header, "L_APPROVED");
        L_ARE_YOU_SURE = ini.get(header, "L_ARE_YOU_SURE");
                    [...]
                                L_WELCOME = ini.get(header, "L_WELCOME");
        L_WELCOME2 = ini.get(header, "L_WELCOME2");
        L_XACT_CHNG = ini.get(header, "L_XACT_CHNG");  
        L_YES = ini.get(header, "L_YES");

        System.err.println("Employee Language: " + header);
    } 
    catch (InvalidFileFormatException e) 
    {
        e.printStackTrace();
    } 
    catch (IOException e) 
    {
        e.printStackTrace();
    }
} // end public static void main

That's for the majority of the strings to be displayed in different languages. There is another method inside Lang that loads some other strings, independent of the first set. I don't believe it factors into this problem but I can post it if needed.

The order in which these classes/methods get launched is as follows: GUI.Main calls the Login class, which calls a CreateLogin method. That method calls Clients.main, which gets the DB_info array from GUI passed to it. Clients fills the DB_info array. Lang.other is then called (to get language-specific strings for the login page), and the Login buttons and labels are created. Once a login is successful, the perferred language of the employee logging in (from a DB) is passed to Lang.main to load the other strings (hence the emp_lang being passed in the code above).

Up until I added the code for the Locale object, all of this worked fine. Now I get the ExceptionInInitializerError exception. Anyone know what's going on?

BTW, for loading from the ini file I'm using ini4j. Some forum posts I found while googling suggest this is a problem with that, but I don't see how it relates to the problem with Locale objects. The ini stuff works (worked) fine.

Answer 1

Sounds like you have a cycle in your static initializers, so something is not initialized yet.

GUI calls Lang's static initializer before getting Lang.L_WELCOME. Lang calls GUIs static initializer in line 2. Your exception trace makes it look like GUI calls Langs static initializer for some reason.

In all, cycles like this mean that someone is going to reference a statically initialized object and get null instead of what they expected to get. In this case, I suspect Lang.java, line 2, is passing two null pointers to the Locale constructor.

Answer 2

As Keith notes, you have a static initializer cycle. To help future readers...

To minimize these bugs, initialize (simple) constants (with no or minimal constructors) before (complex) variables, so here String before Locale – less room for cycles to cause problems.

Debugging-wise, NullPointerException on a static field and 2 <clinit> in stack trace, with the earlier class appearing in the failing line, are the clues that this is an uninitialized field caused by a static initializer cycle.