Lecture 55:-  Sample Problem - Pangram Checking iN Java

A pangram is a sentence or a phrase that contains every letter of the alphabet at least once. To check if a given string is a pangram in Java, you can use the following approach:

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public class PangramChecker {    public static boolean isPangram(String str) {        // Convert the input string to lowercase to handle both uppercase and lowercase letters        str = str.toLowerCase();        // Create a boolean array to mark the presence of letters        boolean[] lettersPresent = new boolean[26];        // Iterate through the string and mark the presence of letters in the array        for (int i = 0; i < str.length(); i++) {            char ch = str.charAt(i);            if (Character.isLetter(ch)) {                int index = ch - 'a';                lettersPresent[index] = true;            }        }        // Check if all letters are present in the array        for (boolean isPresent : lettersPresent) {            if (!isPresent) {                return false;            }        }        return true;    }    public static void main(String[] args) {        String sentence1 = "The quick brown fox jumps over the lazy dog";        String sentence2 = "Hello, World!";                System.out.println(isPangram(sentence1)); // Output: true        System.out.println(isPangram(sentence2)); // Output: false    } }

In this example, we have a method isPangram that takes a string str as input and returns true if it is a pangram and false otherwise. We convert the input string to lowercase using toLowerCase() to handle both uppercase and lowercase letters.

We then create a boolean array lettersPresent of size 26, representing the 26 letters of the English alphabet. We iterate through the string and mark the presence of letters in the array. If the character is a letter, we calculate the index of the letter in the array (0 to 25) by subtracting the ASCII value of 'a' from the character's ASCII value. We set the corresponding element in the lettersPresent array to true.

After processing the entire string, we check if all elements in the lettersPresent array are true. If any letter is missing, we return false, indicating that the string is not a pangram. Otherwise, we return true, indicating that the string is a pangram.

In the main method, we test the isPangram method with two sample sentences, and the output shows whether each sentence is a pangram or not.