Next time, please explain what the error message is that you get instead of just posting the code without any comments at all.
You're probably getting an error message that says the variable doubleVal may not have been initialized.
Look at your code. What happens when Double.parseDouble(Str) throws an exception? Execution goes to the catch block, but the variable doubleVal remains uninitialized. In Java, you must initialize local variables before you refer to them (as you do in the System.out.println(...) statement at the bottom.
I bet you've written a class named "Double" at some point, and your file "Double.class" is still hanging around somewhere. Delete it, and try not to name your own classes the same as common Java API class names!