Java provides java.util.regex package with two main classes: Pattern → Compiles the regex. Matcher → Used to match patterns against text. Basic Example import java.util.regex.*; public class RegexExample { public static void main(String[] args) { String text = "My email is test@example.com"; String regex = "\\w+@\\w+\\.\\w+"; // Simple email regex Pattern pattern = Pattern.compile(regex);…
1. What is Reflection in Java? Reflection is a feature in Java that allows a program to inspect and manipulate classes, methods, fields, and constructors at runtime, even if you don’t know their names at compile time. It’s like having a “mirror” into the internals of a class. Key uses: Inspect class information at…
Let’s go over Palindrome checking in Java. A palindrome is a string, number, or sequence that reads the same forward and backward, e.g., "madam" or "12321". There are multiple ways to check for a palindrome. I’ll cover the common approaches. 1️⃣ Using StringBuilder Reverse Method public class PalindromeCheck { public static boolean isPalindrome(String str)…
Let's go over Anagram checking in Java. An anagram is when two strings have the same characters in a different order, e.g., "listen" and "silent". There are multiple ways to check for anagrams. I’ll cover the most common and efficient methods. Using Sorting Idea: Convert strings to char arrays. Sort both arrays. If they…
Let's go over string reversal in Java. There are several ways to reverse a string, from simple to more advanced. I’ll cover the most common methods. 1️⃣ Using a for loop public class StringReversal { public static String reverseString(String str) { String reversed = ""; for (int i = str.length() - 1; i >=…
Linear Search Algorithm Linear Search checks each element one by one until it finds the target. Works on unsorted or sorted arrays. Time Complexity: O(n) Space Complexity: O(1) Iterative Linear Search public class LinearSearch { public static int linearSearch(int[] arr, int target) { for (int i = 0; i < arr.length; i++) { if…
Binary Search Algorithm Binary Search works on sorted arrays and uses divide-and-conquer: Find the middle element. If it matches the target, return the index. If target < middle, search the left half. If target > middle, search the right half. Repeat until found or range is empty. Time complexity: O(log n)Space complexity: O(1) for…
Problem We want to compute: ab=a×a×a… (b times)a^b = a \times a \times a \dots \; (b \text{ times}) For example: 25=322^5 = 32 34=813^4 = 81 Recursive Idea Base case: If b=0b = 0, return 1 (since a0=1a^0 = 1). Recursive case: ab=a×a(b−1)a^b = a \times a^{(b-1)}. Simple Recursive Code public class PowerRecursion { //…
What is GCD? The Greatest Common Divisor (GCD) of two numbers is the largest positive integer that divides both numbers without leaving a remainder. Examples: GCD(48, 18) = 6 GCD(56, 98) = 14 Recursive Idea (Euclidean Algorithm) The Euclidean algorithm is the most efficient recursive method for GCD: gcd(a,b)={aif b=0gcd(b,a%b)if b≠0\text{gcd}(a, b) = \begin{cases} a &…
What is Fibonacci? The Fibonacci sequence is defined as: F(0)=0,F(1)=1F(0) = 0, \quad F(1) = 1 F(n)=F(n−1)+F(n−2)for n≥2F(n) = F(n-1) + F(n-2) \quad \text{for } n \geq 2 So, the sequence looks like:0, 1, 1, 2, 3, 5, 8, 13, 21 … Recursive Idea Base cases: If n == 0, return 0. If n ==…