how to check if user input is a double?

Question

In my JSP page, I let users input their dollar balance. Then I catch this in servlet as: String input = req.getParameter("balance");

How do I check if input variable is double? I know how to use ParseDouble, but I don't want to catch the exception. Instead, I want to pass my own error message to JSP so that users can see it when they have typing error.

Can someone help me?

possible duplicate of [Java: how to check that a string is parsable to a double?](http://stackoverflow.com/questions/3543729/java-how-to-check-that-a-string-is-parsable-to-a-double) — Martijn Courteaux, Nov 26 '13 at 18:43
Catch the NumberFormatException, and rethrow your own 'MyJspUserException'. — jn1kk, Nov 26 '13 at 18:45

score 4 · Answer 1 · edited Nov 26 '13 at 19:00

4

You may also create a function like this:

boolean isDouble(String input) {
        try {
            Double.parseDouble(input);
            return true;
        } catch (NumberFormatException e) {
            //You can send the message which you want to show to your users here.
            return false;
        }
    }

edited Nov 26 '13 at 19:00

JamesB

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answered Nov 26 '13 at 18:43

Rahul Tripathi

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how to check if user input is a double?

1 Answers1