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Java program to check a given character is alphanumeric or not without using a built-in method

Given/input a character, we have to check a given character is alphanumeric or not without using a built-in method.
Submitted by Nidhi, on February 24, 2022

Problem statement

In this program, we will read a character from the user and check the input character is alphanumeric or not without using any built-in library method.

Java program to check a given character is alphanumeric or not

The source code to check a given character is alphanumeric or not without using the built-in method is given below. The given program is compiled and executed successfully.

// Java program to check a given character is 
// alphanumeric or not without using 
// the built-in method

import java.util.Scanner;

public class Main {
  static boolean isAlphaNumeric(char ch) {
    if ((ch >= '0' & ch <= '9') || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
      return true;
    return false;
  }

  public static void main(String[] args) {
    Scanner X = new Scanner(System.in);

    char ch = 0;

    System.out.printf("Enter character: ");
    ch = X.next().charAt(0);

    if (isAlphaNumeric(ch))
      System.out.printf("Given character is an alphanumeric character\n");
    else
      System.out.printf("Given character is not an alphanumeric character\n");
  }
}

Output

RUN 1:
Enter character: K
Given character is an alphanumeric character

RUN 2:
Enter character: 8
Given character is an alphanumeric character

RUN 3:
Enter character: %
Given character is not an alphanumeric character

Explanation

In the above program, we imported "java.util.Scanner" package to read input from the user. And, created a public class Main. It contains two static methods main() and isAlphaNumeric().

The isAlphaNumeric() method returns a Boolean value based on input character, it returns true if the given character is alphanumeric otherwise it returns false.

The main() method is an entry point for the program. Here, we read a character from the user and checked input character is alphanumeric or not and printed the appropriate message.

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