Regex to allow only a single dot in a textbox

Question

I have one text input.

I wrote a regex for masking all special characters except . and -. Now if by mistake the user enters two .

Answer 1

You can probably avoid regex altogether with this case.

For instance

String[] input = { "225.36", "225..36","-225.36", "-225..36" };
for (String s : input) {
    try {
        Double d = Double.parseDouble(s);
        System.out.printf("\"%s\" is a number.%n", s);
    }
    catch (NumberFormatException nfe) {
        System.out.printf("\"%s\" is not a valid number.%n", s);
    }
}

Output

"225.36" is a number.
"225..36" is not a valid number.
"-225.36" is a number.
"-225..36" is not a valid number.