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A Progressive Web App (PWA) is a type of web application that uses modern web technologies to deliver an experience similar to native mobile or desktop apps. PWAs are built with standard web technologies (HTML, CSS, JavaScript) but have enhanced capabilities like offline access, push notifications, installability, and fast performance. They’re called progressive because…

System Design Principles are the fundamental guidelines and best practices used to build scalable, maintainable, and reliable software systems. They help backend developers and architects make decisions about architecture, data flow, and infrastructure to handle real-world requirements like performance, reliability, and growth. Here’s a detailed breakdown: 1. Scalability Ability of a system to handle…

1. Array → Collection (List/Set) Java provides multiple ways to convert an array into a collection (usually a List or Set). ✅ Using Arrays.asList() import java.util.*; public class Main { public static void main(String[] args) { String[] array = {"Java", "Python", "C++"}; // Convert to List List<String> list = Arrays.asList(array); System.out.println(list); // [Java, Python,…

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…