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 OJC {

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 OJC {

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 OJC {

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

Source: geeksforgeeks.org