How to handle a static final field initializer tha

问题:

I am facing a use case where I would like to declare a static finalfield with an initializer statement that is declared to throw a checked exception. Typically, it'd look like this:

public static final ObjectName OBJECT_NAME = new ObjectName("foo:type=bar");

The issue I have here is that the ObjectName constructor may throw various checked exceptions, which I don't care about (because I'd know my name is valid, and it's allright if it miserably crashes in case it's not). The java compiler won't let me just ignore this (as it's a checked exception), and I would prefer not to resort to:

public static final ObjectName OBJECT_NAME;
static{
    try{
        OBJECT_NAME = new ObjectName("foo:type=bar");
    }catch(final Exception ex){
        throw new RuntimeException("Failed to create ObjectName instance in static block.",ex);
    }  
}

Because static blocks are really, really difficult to read. Does anyone have a suggestion on how to handle this case in a nice, clean way?

回答1:

If you don't like static blocks (some people don't) then an alternative is to use a static method. IIRC, Josh Bloch recommended this (apparently not in Effective Java on quick inspection).

public static final ObjectName OBJECT_NAME = createObjectName("foo:type=bar");

private static ObjectName createObjectName(final String name) {
    try {
        return new ObjectName(name);
    } catch (final SomeException exc) {
        throw new Error(exc);
    }  
}

Or:

public static final ObjectName OBJECT_NAME = createObjectName();

private static ObjectName createObjectName() {
    try {
        return new ObjectName("foo:type=bar");
    } catch (final SomeException exc) {
        throw new Error(exc);
    }  
}

(Edited: Corrected second example to return from method instead of assign the static.)

回答2:

Your code is perfectly valid. I don't find it difficult to read. Other ways would only make it more worse. They're only difficult to read for starters, because most of them are not familiar with that. Just follow the standard conventions with regard to ordering of the elements in the code. E.g. do not put static initializers halfway or at the whole bottom of the code and also do not have multiple of them spreading over the class. Just put one at top, after static declarations.

回答3:

static blocks aren't difficult to read. So I'd recommend that solution. However, you can wrap your object in another object, for example ObjectNameWrapper which shares an interface with your ObjectName, and whose constructor calls your ObjectName constructor, hiding all checked exceptions that occur. But again, I'd go for the static option.