Java Character IsDigit Method

Introduction

In this lab, we will learn about Java isDigit(char ch) method, which is a part of Character class. This method checks whether the specified character is a digit or not.

Create a Java file.

Firstly, we need to create a Java file in the ~/project directory. You can use any text editor such as nano, vi editor, or simply use an IDE such as Eclipse, NetBeans, IntelliJ, etc.

Name the file IsDigitExample.java. You can use the following command to create a file using the terminal:

touch ~/project/IsDigitExample.java

Define the class.

Define the class IsDigitExample.

public class IsDigitExample {

Define the main method.

Define the main method inside the IsDigitExample class. This method executes the code and creates objects.

public static void main(String[] args) {

Check whether the specified character is a digit or not.

Use the isDigit(char ch) method of the Character class to check whether the specified character is a digit or not. If the passed character is a digit, then this method returns true, otherwise, it returns false.

 char ch1 = 'A';
 char ch2 = 'u';
 char ch3 = '8';

 boolean b1 = Character.isDigit(ch1);
 boolean b2 = Character.isDigit(ch2);
 boolean b3 = Character.isDigit(ch3);
 System.out.println(ch1 + " is a digit??:  " + b1);
 System.out.println(ch2 + " is a digit??:  " + b2);
 System.out.println(ch3 + " is a digit??:  " + b3);

Compile the Java file.

After writing the Java code, compile the code with the following command:

javac IsDigitExample.java

Run the Java program.

After compiling the Java code, run the program with the following command:

java IsDigitExample

Test the output with user input.

Create a new method named userDefinedExample() inside the IsDigitExample class.

public static void userDefinedExample() {
  try {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Enter the character: ");
    char ch = scanner.next().charAt(0);
    boolean result = Character.isDigit(ch);
    System.out.println(ch + " is a digit?? : " + result);
  } catch (Exception e) {
    System.out.println("Invalid Input!!");
  }
}

Invoke the userDefinedExample() method.

Invoke the userDefinedExample() method in the main() method.

System.out.println("Execution character digit check example:");
characterDigitCheck();
System.out.println("\nUser Defined Example:");
userDefinedExample();

Compile and run the program.

Compile and run the program again with the same commands as in steps 5 and 6.

javac IsDigitExample.java
java IsDigitExample

Summary

In this lab, we learned how to check whether a specified character is a digit or not using the Java isDigit(char ch) method. We also learned how to create a user-defined example, take input from the user and verify the output. This method is helpful when we need to validate certain types of user input.