Numbers only regex (digits only) Java
Numbers only (or digits only) regular expressions can be used to validate if a string contains only numbers.
Basic numbers only regex
Below is a simple regular expression that allows validating if a given string contains only numbers:
Pattern.compile("^\\d+$")
Enter a text in the input above to see the result
Example code in Java:
import java.util.regex.Pattern;
import java.util.regex.MatchResult;
import java.util.Arrays;
public class Main {
public static void main(String []args) {
// Validate number
boolean isMatch = Pattern.compile("^\\d+$")
.matcher("42")
.find();
System.out.println(isMatch); // prints true
// Extract number from a string
String[] matches = Pattern.compile("\\d+")
.matcher("Your message was viewed 203 times.")
.results()
.map(MatchResult::group)
.toArray(String[]::new);
System.out.println(Arrays.toString(matches)); // prints [203]
}
}
Real number regex
Real number regex can be used to validate or exact real numbers from a string.
Pattern.compile("^(?:-(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))|(?:0|(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))))(?:.\\d+|)$")
Enter a text in the input above to see the result
Example code in Java:
import java.util.regex.Pattern;
import java.util.regex.MatchResult;
import java.util.Arrays;
public class Main {
public static void main(String []args) {
// Validate real number
boolean isMatch = Pattern.compile("^(?:-(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))|(?:0|(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))))(?:.\\d+|)$")
.matcher("121220.22")
.find();
System.out.println(isMatch); // prints true
// Extract real number from a string
String[] matches = Pattern.compile("(?:-(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))|(?:0|(?:[1-9](?:\\d{0,2}(?:,\\d{3})+|\\d*))))(?:.\\d+|)")
.matcher("Pi equals to 3.14")
.results()
.map(MatchResult::group)
.toArray(String[]::new);
System.out.println(Arrays.toString(matches)); // prints [3.14]
}
}
Notes on number only regex validation
In Java you can also validate number by trying to parse it:
try {
double d = Double.parseDouble("1.12");
} catch (NumberFormatException nfe) {
return false;
}
