Having null in a value of a ListResourceBundle implementation

Question

In a ListResourceBundle implementation I define an array with some keys containing null values. It compiles fine the loading process of the bundle containing a null value. However when I call getObject on a key with a non-null value (like in the following example "Pollution" which has value "high"), it gives me a NullPointerException.

Do you have an idea why it happens in that way?

ResourceBundle labels = ResourceBundle.getBundle("bundlething", new Locale("it"));
labels.getObject("Pollution");// here NullPointerException, However Pollution has a \n

value, other keys of the same array do not.

UPDATE: This is the stacktrace I receive:

Exception in thread "main" java.lang.NullPointerException at java.util.ListResourceBundle.loadLookup(ListResourceBundle.java:196) at java.util.ListResourceBundle.handleGetObject(ListResourceBundle.java:124) at java.util.ResourceBundle.getObject(ResourceBundle.java:387) at ResourceBundleThing.main(ResourceBundleThing.java:38)

and this is the bundle I load by passing new Locale("it") as target Locale:

import java.util.ListResourceBundle;
public class bundlething_it extends ListResourceBundle {

    private  Object [][] contents  ={{"Inhabitants",null},{"Pollution",new Double(3.4034)},{"Lollerball",new Integer(132)}};
    public Object[][] getContents()
    {
        return contents;
    }

}

There is null corresponding to "Inhabitans" however I am referring only to "Pollution" which has a non-null value. Still I get a NullPointerException; If I remove that null from "Inhabitants" it works.. so it's there the problem, I know. However I would like to know why since I am not using that particular key-value pair. Does it load all the values as soon as getObject it's called?

Thanks in advance.

Answer 1

The stack trace precisely indicates where the error comes from:

    Object[][] contents = getContents();
    HashMap<String,Object> temp = new HashMap<>(contents.length);
    for (int i = 0; i < contents.length; ++i) {
        // key must be non-null String, value must be non-null
        String key = (String) contents[i][0];
        Object value = contents[i][1];
        if (key == null || value == null) {
            throw new NullPointerException(); // <-- HERE
        }
        temp.put(key, value);
    }

So, you have your answer: although I haven't seen it mentioned in the documentation, ListResourceBundle doesn't allow null values.