Initializing a static Class variable known at compile time in Java

Question

I want to initialize a static Class variable in Java:

public class NumberExpression {
    private static Class numberClass = Class.forName("java.lang.Number");
};

The above code segment doesn't work because Class.forName throws a ClassNotFoundException. Something like new Integer().getClass() won't work because Number is an abstract class.

I suppose I could wrap Class.forName around a static method that handles the ClassNotFoundException, but is there a more elegant/standard way of getting what I want?

Edit:

(class "Number" changed to "java.lang.Number")

Francisco Spaeth · Accepted Answer · 2012-06-23 23:41:30Z

5

It doesn't work because the class Number doesn't exist. What you meant was java.lang.Number.

You could try something like:

public class NumberExpression {
    private static Class numberClass;
    static {
        try {
            numberClass = Class.forName("java.lang.Number");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
};

But this just makes sense when the class that you are trying to load is dynamic, otherwise you could use the class it self (i.e. Number.class)

edited Jun 23, 2012 at 23:41

answered Jun 23, 2012 at 23:33

Francisco Spaeth

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6 Comments

math4tots Over a year ago

Yes, you're right. But even after I change it, the compiler still complains that the exception needs to be caught.

Oliver Charlesworth Over a year ago

@math4tots: Then catch the exception!

math4tots Over a year ago

@OliCharlesworth How? it's a static variable, so I don't know where I should set it. From what I understand, I don't think I can catch exceptions in a class body...

Francisco Spaeth Over a year ago

@math4tots: please take a look into my update ;) What I'm doing there is creating a static block, and within this static block the numberClass is set.

math4tots Over a year ago

That is really cool that you can do that. However I think Dalkitsis had exactly the solution I needed.

|

Savvas Dalkitsis · Accepted Answer · 2012-06-23 23:40:01Z

4

Why don't you do :

private Class numberClass = Number.class;

answered Jun 23, 2012 at 23:40

Savvas Dalkitsis

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