Character isDigit() method in Java with examples

1. The java.lang.Character.isDigit(char ch) is an inbuilt method in java which determines whether a specified character is a digit or not. There are few conditions that a character must accomplish to be accepted as a digit. That is if the general category type of a character, provided by Character.getType(ch), is DECIMAL_DIGIT_NUMBER, then the character is a digit.
   Some Unicode character ranges that contain digits:

   From ‘\u0030’ to ‘\u0039’ : ISO-LATIN-1 digits (‘0’ through ‘9’)
   From ‘\u0660’ to ‘\u0669’ : Arabic-Indic digits
   From ‘\u06F0’ to ‘\u06F9’ : Extended Arabic-Indic digits
   From ‘\u0966’ to ‘\u096F’ : Devanagari digits
   From ‘\uFF10’ to ‘\uFF19’ : Fullwidth digits

   Apart from the above mentioned ranges, many other character ranges contain digits as well.

   Syntax:

   public static boolean isDigit(char ch)
   

   Parameter: This method accepts character parameter ch as an argument, which is to be tested.

   Return value:This method returns a boolean value. It returns True if ch is digit, else False.

   Note: This method cannot handle supplementary characters. To support all Unicode characters, including supplementary characters, use the isDigit(int) method.

   Below programs illustrate the above method:
   Program 1:

   // Java program to illustrate the
   // Character.isDigit() method
   
   import java.util.*;
   import java.lang.*;
   
   public class GFG {
   
       public static void main(String[] args)
       {
   
           // two characters
           char c1 = 'A', c2 = '4';
   
           // Function to check if the character
           // is digit or not
           System.out.println(
               c1 + " is a digit -> "
               + Character.isDigit(c1));
           System.out.println(
               c2 + " is a digit -> "
               + Character.isDigit(c2));
       }
   }
   Output:

   A is a digit -> false
   4 is a digit -> true
   

   Program 2:

   // Java program to illustrate the
   // Character.isDigit() method
   
   import java.util.*;
   import java.lang.*;
   
   public class GFG {
   
       public static int search_digit(String s)
       {
   
           // Function to check if is digit
           // is found or not
           for (int i = 0; i < s.length(); i++) {
               if (Character.isDigit(
                       s.charAt(i))
                   == true) {
                   // return position of digit
                   return i + 1;
               }
           }
           // return 0 if digit not present
           return 0;
       }
   
       public static void main(String[] args)
       {
   
           // Array of strings
           String[] arr = { "ABC4DEF", "QWERTY" };
   
           // To store the position of digit
           int index = 0;
   
           // Traverse the array arr[] to find digit
           // within it's elements
           for (String x : arr) {
               index = search_digit(x);
               if (index != 0) {
                   System.out.println(
                       "Digit found at : "
                       + (index)
                       + "th position.");
               }
               else {
                   System.out.println(
                       "Digit not present.");
               }
           }
       }
   }
   Output:

   Digit found at : 4th position.
   Digit not present.
   

2. The java.lang.Character.isDigit(int codePoint) is an inbuilt method in java which determines whether the specified Unicode code point character of integer type is a digit or not.
   There are few conditions that a character must accomplish to be accepted as a digit. That is if the general category type of a character, provided by getType(codepoint), is a DECIMAL_DIGIT_NUMBER, then the character is a digit. Some Unicode character ranges that contain digits:

   From ‘\u0030’ to ‘\u0039’ : ISO-LATIN-1 digits (‘0’ through ‘9’)
   From ‘\u0660’ to ‘\u0669’ : Arabic-Indic digits
   From ‘\u06F0’ to ‘\u06F9’ : Extended Arabic-Indic digits
   From ‘\u0966’ to ‘\u096F’ : Devanagari digits
   From ‘\uFF10’ to ‘\uFF19’ : Fullwidth digits

   Apart from the above mentioned ranges, many other character ranges contain digits as well.

   Syntax:

   public static boolean isDigit(int codePoint)
   

   Parameter: This method accepts unicode character parameter codePoint of integer type as an argument, which is to be tested.

   Return value: This method returns a boolean value. It returns True if the specified character is digit, else it returns False.

   Below programs illustrate the above method:
   Program 1:

   // This program demonstrates the use of
   // isDigit(int codePoint) method of Character class.
   import java.util.*;
   
   public class GFG {
       public static void main(String[] args)
       {
           // create codePoints
           int cp1 = 57;
           int cp2 = 84;
   
           // Check whether the codePoints
           // are digit or not.
           System.out.println(
               "The codePoint cp1 is a digit -> "
               + Character.isDigit(cp1));
           System.out.println(
               "The codePoint cp2 is a digit -> "
               + Character.isDigit(cp2));
       }
   }
   Output:

   The codePoint cp1 is a digit -> true
   The codePoint cp2 is a digit -> false
   

   Program 2:

   // This program demonstrates the use of
   // isDigit(int codePoint) method of
   // Character class.
   import java.util.*;
   
   public class Main {
       public static void main(String[] args)
       {
           // create codePoints
           int cp1 = 0x50;
           int cp2 = 0x06f8;
   
           // Check whether the codePoints
           // are digit or not.
           System.out.println(
               "The codePoint cp1 is a digit -> "
               + Character.isDigit(cp1));
           System.out.println(
               "The codePoint cp2 is a digit -> "
               + Character.isDigit(cp2));
       }
   }
   Output:

   The codePoint cp1 is a digit -> false
   The codePoint cp2 is a digit -> true
   

   Reference: https://docs.oracle.com/javase/8/docs/api/java/lang/Character.html#isDigit-char-