println it

Software blog about tools, builds and making it all work

An importance of wrapping variables



Long time ago I’ve developed a habit of wrapping every variable logged in [ .. ]:

Java:   log.error( "Class [" + c + "] not found" )
Java:   log.error( String.format( "Class [%s] not found", c ))
Groovy: log.error( "Class [$c] not found" )

The reasons were mostly to spot any trailing whitespaces in variables logged which was very helpful in error messages. As simple as it sounds, lots of messages thrown or logged today still don’t enclose variables in any special characters which can make them quite obscure.

What would you say about this error message ?

..
java.lang.IllegalArgumentException: No enum const class Something.
	at java.lang.Enum.valueOf(Enum.java:196)
..

I was surprised why failing Enum.valueOf() didn’t include the wrong value in the error message. But it did! Here’s the failing code:

..
enum Something{ A, B }
assert Something.A != Something.valueOf( '' )
..

So it was an empty String. Normally, wrong Enum.valueOf() input is printed:

..
enum Something{ A, B }
assert Something.A != Something.valueOf( 'C' )


java.lang.IllegalArgumentException: No enum const class Something.C
	at java.lang.Enum.valueOf(Enum.java:196)
..

But with empty argument "No enum const class Something." simply looked like a period at the end of the sentence! I wish it was "No enum const class [Something.]" instead.

// "java/lang/Enum.java"
public static <T extends Enum<T>> T valueOf(Class<T> enumType,
                                            String name) {
    T result = enumType.enumConstantDirectory().get(name);
    if (result != null)
        return result;
    if (name == null)
        throw new NullPointerException("Name is null");
    throw new IllegalArgumentException(
        "No enum const " + enumType +"." + name);
}

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>