Tech Jargon - Decoded

#Java #StringManipulation #ToggleCase

Toggle Case of String

public class Main {
    public static String toggleCase(String str) {
        StringBuilder result = new StringBuilder();
        for (char c : str.toCharArray()) {
            if (Character.isUpperCase(c)) {
                result.append(Character.toLowerCase(c));
            } else if (Character.isLowerCase(c)) {
                result.append(Character.toUpperCase(c));
            } else {
                result.append(c);
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        String input = "Hello World!";
        String toggled = toggleCase(input);
        System.out.println("Original: " + input);
        System.out.println("Toggled: " + toggled);
    }
}

#Java #StringRotation #StringManipulation

Check if Two Strings are Rotation of Each Other

public class StringRotation {
    public static boolean areRotations(String str1, String str2) {
        if (str1 == null || str2 == null || str1.length() != str2.length()) {
            return false;
        }
        if (str1.length() == 0) {
            return true;
        }
        String temp = str1 + str1;
        return temp.contains(str2);
    }

    public static void main(String[] args) {
        String str1 = "ABCD";
        String str2 = "CDAB";
        if (areRotations(str1, str2))
            System.out.println("Strings are rotations of each other");
        else
            System.out.println("Strings are not rotations of each other");
    }
}

#Java #StringManipulation #HashMap

Find First Non-Repeating Character

import java.util.HashMap;
import java.util.Map;

public class FirstNonRepeatingCharacter {

    public static Character findFirstNonRepeating(String str) {
        Map<Character, Integer> charCounts = new HashMap<>();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            charCounts.put(c, charCounts.getOrDefault(c, 0) + 1);
        }

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (charCounts.get(c) == 1) {
                return c;
            }
        }

        return null;
    }

    public static void main(String[] args) {
        String input = "programming";
        Character result = findFirstNonRepeating(input);
        System.out.println("First non-repeating character: " + result);
    }
}

#Java #StringManipulation #Duplicates

Remove Duplicate Characters

import java.util.LinkedHashSet;
import java.util.Set;

public class RemoveDuplicates {

    public static String removeDuplicates(String str) {
        Set<Character> set = new LinkedHashSet<>();
        for (char c : str.toCharArray()) {
            set.add(c);
        }

        StringBuilder sb = new StringBuilder();
        for (Character c : set) {
            sb.append(c);
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        String input = "programming";
        String result = removeDuplicates(input);
        System.out.println("Original string: " + input);
        System.out.println("String with duplicates removed: " + result);
    }
}

#Java #StringManipulation #CharacterCount

Count Vowels, Consonants, Digits, Whitespaces in a String

public class StringCounter {

    public static void main(String[] args) {
        String str = "Hello World 123! This is a Test String.";
        int vowels = 0;
        int consonants = 0;
        int digits = 0;
        int spaces = 0;

        str = str.toLowerCase();

        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);

            if (ch >= 'a' && ch <= 'z') {
                if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
                    vowels++;
                } else {
                    consonants++;
                }
            } else if (ch >= '0' && ch <= '9') {
                digits++;
            } else if (ch == ' ') {
                spaces++;
            }
        }

        System.out.println("Vowels: " + vowels);
        System.out.println("Consonants: " + consonants);
        System.out.println("Digits: " + digits);
        System.out.println("Whitespaces: " + spaces);
    }
}

#Java #Anagram #Strings

Check Anagram Strings

import java.util.Arrays;

public class AnagramChecker {

    public static boolean areAnagrams(String str1, String str2) {
        if (str1.length() != str2.length()) {
            return false;
        }

        char[] charArray1 = str1.toCharArray();
        char[] charArray2 = str2.toCharArray();

        Arrays.sort(charArray1);
        Arrays.sort(charArray2);

        return Arrays.equals(charArray1, charArray2);
    }

    public static void main(String[] args) {
        String str1 = "listen";
        String str2 = "silent";

        if (areAnagrams(str1, str2)) {
            System.out.println(str1 + " and " + str2 + " are anagrams.");
        } else {
            System.out.println(str1 + " and " + str2 + " are not anagrams.");
        }
    }
}

#Java #Palindrome #String

Check Palindrome String (Ignore Case)

public class Palindrome {
    public static boolean isPalindrome(String str) {
        str = str.replaceAll("[^a-zA-Z0-9]", "").toLowerCase();
        int left = 0;
        int right = str.length() - 1;
        while (left < right) {
            if (str.charAt(left) != str.charAt(right)) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }

    public static void main(String[] args) {
        String testString1 = "Racecar";
        String testString2 = "A man, a plan, a canal: Panama";
        String testString3 = "hello";

        System.out.println("\"" + testString1 + "\" is a palindrome: " + isPalindrome(testString1));
        System.out.println("\"" + testString2 + "\" is a palindrome: " + isPalindrome(testString2));
        System.out.println("\"" + testString3 + "\" is a palindrome: " + isPalindrome(testString3));
    }
}

#Java #StringReverse #Recursion

Reverse a String (Iterative & Recursive)

public class StringReverser {

    public static String reverseIterative(String str) {
        StringBuilder reversed = new StringBuilder();
        for (int i = str.length() - 1; i >= 0; i--) {
            reversed.append(str.charAt(i));
        }
        return reversed.toString();
    }

    public static String reverseRecursive(String str) {
        if (str == null || str.isEmpty()) {
            return str;
        }
        return reverseRecursive(str.substring(1)) + str.charAt(0);
    }

    public static void main(String[] args) {
        String input = "hello";
        String reversedIterative = reverseIterative(input);
        String reversedRecursive = reverseRecursive(input);
        System.out.println("Original string: " + input);
        System.out.println("Reversed (Iterative): " + reversedIterative);
        System.out.println("Reversed (Recursive): " + reversedRecursive);
    }
}

#Java #StringReverse #Iterative #Recursive

Reverse a String (Iterative & Recursive)

public class StringReverser {    public static String reverseIterative(String str) {        StringBuilder reversed = new StringBuilder();        for (int i = str.length() - 1; i >= 0; i--) {            reversed.append(str.charAt(i));        }        return reversed.toString();    }    public static String reverseRecursive(String str) {        if (str.isEmpty()) {            return str;        }        return reverseRecursive(str.substring(1)) + str.charAt(0);    }    public static void main(String[] args) {        String input = "Hello";        System.out.println("Original string: " + input);        System.out.println("Reversed (iterative): " + reverseIterative(input));        System.out.println("Reversed (recursive): " + reverseRecursive(input));    }}

#Java #PrimeNumbers #SieveOfEratosthenes #Algorithm #Interview

Count Primes Less than N

public class PrimeCounter {

    public static int countPrimes(int n) {
        if (n <= 2) {
            return 0;
        }

        boolean[] isPrime = new boolean[n];
        for (int i = 2; i < n; i++) {
            isPrime[i] = true;
        }

        for (int i = 2; i * i < n; i++) {
            if (!isPrime[i]) continue;
            for (int j = i * i; j < n; j += i) {
                isPrime[j] = false;
            }
        }

        int count = 0;
        for (int i = 2; i < n; i++) {
            if (isPrime[i]) count++;
        }

        return count;
    }

    public static void main(String[] args) {
        int n = 10;
        int primeCount = countPrimes(n);
        System.out.println("Number of primes less than " + n + " is: " + primeCount);
    }
}