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

if you just want to handle number ,you can try this:

valueTest.match(/^-?\d+(\.\d+)?$/)

Answer 2

I think you mean this,

^-?\d+(?:\.\d+)?$

DEMO

It allows positive and negative numbers with or without decimal points.

EXplanation:

• ^ Asserts that we are at the start.
• -? Optional - symbol.
• \d+ Matches one or more numbers.
• (?: start of non-capturing group.
• \. Matches a literal dot.
• \d+ Matches one or more numbers.
• ? Makes the whole non-capturing group as optional.
• $ Asserts that we are at the end.

Answer 3

Use below reg ex it will meet your requirements.

/^\d+(.\d+)?$/

Answer 4

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.