检查字符串是否为数字

Question

I am trying to check whether a string is a number. I have tried the following, which works separately but not together.

if (i.matches("\\d{2} | [0-9]"))

I appreciate any help.

Answer 1

I think you're trying to check whether the given string is a one or two digit number or not.

if (i.matches("\\d{1,2}"))

Note that matches method won't need anchors. It would do an exact string match.

Answer 2

You can use Exception mechanism to provided by Java to address this problem.

The constructor BigInteger(String val) of class BigInteger throws NumberFormatException if the provided string is not a valid decimal number.

public static boolean isNumber(String string) {
    if (string != null) {
        try {
            new BigInteger(string);
            return true;
        } catch (NumberFormatException nfe) {
            return false;
        }
    }
    return false;
}

You can also use another constructor of class BigInteger - BigInteger(String val, int radix) to check whether the provided string is a number with base radix .

Eg: 76576ACFED65 is a valid number with base 16.