Check if a String is Numeric in Java

public class IsNumeric {
    public static void main(String[] args) {
  
        String string = "1786.3873";
        boolean numeric = true;
        try {
            Double num = Double.parseDouble(string);
        } catch (NumberFormatException e) {
            numeric = false;
        }
  
        if(numeric)
            System.out.println(string + " is a numeric value");
        else
            System.out.println(string + " is not a numeric value");
     }
} 

1786.3873 is a numeric value

• This program deals with finding out if the contents of a given string are of numeric value or not.
• Here a string having a value 1786.3873 is stored in a String type variable named string.
• Also a ‘boolean’ type variable ‘numeric’ is initialized having ‘true’ as its value primarily.
• The try and catch segment deals with verifying whether the string possesses a numeric value or not.
• For this purpose, first the string is passed to parseDouble() method to convert the string to its double value equivalent.
• If the string is not a numeric value, then an exception by the name of NumberFormatException is thrown and the value of ‘numeric’ is changes to ‘false’.
• If the value of ‘numeric’ is a number, then an output is displayed on the console.

public class Numeric {
    public static void main(String[] args) {
  
        String string = "9.876ty";
        boolean numeric = true;
        numeric = string.matches("-?\\d+(\\.\\d+)?");
  
        if(numeric)
            System.out.println(string + " is a numeric value");
        else
            System.out.println(string + " is not a numeric value");
    }
} 

9.876ty is not a numeric value

• This program deals with finding out if the contents of a given string are of numeric value or not by employing regular expressions.
•  Unlike the previous example, try-catch method has not been employed in this example.
• The matches() function is called upon the given string having a value of 9.876ty.
• A regular expression is passed within mathes(), that check different parts of the string in order to verify if it is numeric or not.
• The first figment of regular expression i.e. ‘-?’ checks whether there exists a negative sign or not.
• Whereas the second figment ‘\\d+’ whether there exists a number or not. (at-least one number should exist)
• The next segment (‘\\. \\d+’) has two parts further: ‘\\.’ Verifies whether there exists a decimal point.
• If so is the case, then the next part ‘\\d+’ makes sure that there must be one number at least. (More numbers can follow too!).
•  The output depicts that 9.876ty is not a numrical value .