Why aren't format() and parseDouble() or parseInt() compatible??

Question

Hello, I display numbers to the user in their default locale format with:
NumberFormat.getInstance().format(number)
For example, here in the United States, I get a string with commas separating every 3 digits.
However, when the user naturally wants to use the same format in the input, then
Double.parseDouble(string), or Integer.parseInt(string)
throw exceptions, because they don't like the commas.
This is strange - shouldn't parseDouble and parseInt, accept any locale formatted strings, or, if that would be ambiguous, shouldn't there be a way to tell them what locale we are using?
I can't just delete the commas myself, because in a different locale, God-knows-what will be there.
So how do I parse a number string, in a default locale, to a double?? Thank you for any hints.
Mark

Answer 1

No, does not work. This only formats from the beginning of the string, leaving the end if there is junk there. So if the user input a "O" for example, instead of zero at the end, they will wonder why the number did not increase. Worse yet, if they input a legitimate string, such as 2.0e6 (which is a good way to input big numbers in a text field), that will not be formatted, but Double.formatDouble() does format it (it just does not like commas).
To the others answering, thank you for your opinions, but I want the user to be able to input the numbers the same way they are outputted. This is natural way for them to react and it would be unreasonable for me to prevent them.
As to why I don't want to strip commas myself , I already explained.