I want to check whether the String contains only numeric characters or it contains alpha-numeric characters too.
I have to implement this check in database transaction where about a hundred-thousand records are going to be fetched and passed through this check, so I need optimized performance answer.
Currently, I have implemented this through a try-catch block: I parsed the string in Integer in try block and checked for the NumberFormatException in the catch block. Please suggest if I'm wrong.
You can check this with a regex.
Suppose that (numeric values only):
String a = "493284835";
a.matches("^[0-9]+$"); // returns true
Suppose that (alphanumeric values only):
String a = "dfdf4932fef84835fea";
a.matches("^([A-Za-z]|[0-9])+$"); // returns true
As Pangea said in the comments area :
If the performance are critical, it's preferrable to compile the regex. See below for an example :
String a = "dfdf4932fef84835fea";
Pattern pattern = Pattern.compile("^([A-Za-z]|[0-9])+$");
Matcher matcher = pattern.matcher(a);
if (matcher.find()) {
// it's ok
}
Just Googling, I found out this link
public boolean containsOnlyNumbers(String str) {
//It can't contain only numbers if it's null or empty...
if (str == null || str.length() == 0)
return false;
for (int i = 0; i < str.length(); i++) {
//If we find a non-digit character we return false.
if (!Character.isDigit(str.charAt(i)))
return false;
}
return true;
}
Edit: A RegExp to check numeric should be :
return yourNumber.matches("-?\\d+(.\\d+)?");
isDigit() is not just 0-9!