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

Program/Source Code:

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

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

import java.util.Scanner;

public class Main {
  static boolean isUppercase(char ch) {
    if (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 (isUppercase(ch))
      System.out.printf("Given character is an uppercase character\n");
    else
      System.out.printf("Given character is not an uppercase character\n");
  }
}

Output:

RUN 1:
Enter character: x
Given character is not an uppercase character

RUN 2:
Enter character: Y
Given character is an uppercase character

Explanation:

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

The isUppercase() method returns a Boolean value based on input character, it returns true if a given character is an uppercase character 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 an uppercase character or not and printed the appropriate message.