Need help to understand how Objects are rendered in an ftl template

[Jacopo Cappellato]

Let's say that, in the context of an ftl template, I have a double variable:
context.put("doubleVariable", new Double(0.123456));

The following code inside an ftl template:

Double: ${doubleVariable}
Double.toString(): ${doubleVariable.toString()}

is rendered in this way:

Double: 0.123 (WRONG!!!)
Double.toString(): 0.123456 (CORRECT)

Why is this happening?
I think that this is a pretty serious thing since all the numeric fields 
(e.g. in widgets) are affected by this and the numbers displayed on 
screen can be incorrect.

Thanks!

Jacopo