Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java program is designed to teach fundamental input/output and conditional logic. It prompts the user to enter a single character. The program then checks if the input is indeed a single alphabet character. If it's not, it displays an error message. If it is a single alphabet character, it determines whether that character is a vowel or a consonant and prints the result.

Here's a step-by-step breakdown of the logic:

1. Import Scanner: The program starts by importing the Scanner class from the java.util package. The Scanner class is essential for reading user input from the console.
2. Create Scanner Object: Inside the main method, a Scanner object named input is created. This object is linked to the standard input stream (System.in), which typically represents the keyboard.
3. Prompt User: The program displays a message asking the user to "Enter a single character: ".
4. Read User Input: The input.next() method reads the next token (word or sequence of characters separated by whitespace) entered by the user and stores it as a String in the variable s.
5. Input Validation:
   • The if statement checks for invalid input.
   • s.length() != 1: This condition checks if the length of the entered string s is not equal to 1. If the user enters more than one character or nothing at all, this part of the condition will be true.
   • !Character.isLetter(s.charAt(0)): This condition checks if the first character of the input string s is not a letter. s.charAt(0) gets the first character, and Character.isLetter() returns true if it's an alphabet character. The ! negates this, so it's true if the character is not a letter (e.g., a number, symbol, or space).
   • The || (OR) operator means that if either of these conditions is true, the entire if condition is true, and the error message is printed.
6. Error Message: If the input is invalid (not a single character or not a letter), the program prints "Error: Please enter only a single alphabet character".
7. Vowel/Consonant Check (if input is valid):
   • If the input passes the validation (meaning it's a single alphabet character), the else block is executed.
   • char c = Character.toLowerCase(s.charAt(0));: The first character of the input string (s.charAt(0)) is converted to lowercase using Character.toLowerCase() and stored in a char variable named c. This makes the vowel check case-insensitive (so 'A' is treated the same as 'a').
   • The inner if statement checks if the lowercase character c is equal to 'a', 'e', 'i', 'o', or 'u'.
   • Vowel Output: If c matches any of these vowels, "Vowel" is printed.
   • Consonant Output: If c does not match any of the vowels, it must be a consonant (since we've already confirmed it's a letter), so "Consonant" is printed.
8. Close Scanner: Finally, input.close() is called to release the system resources used by the Scanner object. This is good practice.

Algorithm

• Start the program.
• Initialize a Scanner object to read user input.
• Prompt the user to enter a single character.
• Read the user's input as a string.
• Validate Input:
  • Check if the length of the input string is exactly 1.
  • Check if the first character of the input string is an alphabet letter.
  • If the input is not a single alphabet character (either length is not 1 OR the character is not a letter), print an error message.
• Process Valid Input:
  • If the input is a single alphabet character:
    • Convert the character to lowercase.
    • Check if the lowercase character is one of 'a', 'e', 'i', 'o', 'u'.
    • If it is a vowel, print "Vowel".
    • Otherwise (if it's not a vowel and is a letter), print "Consonant".
• Close the Scanner object.
• End the program.