JavaWith.NextlevelCoders

Q. Difference between @Controller and @RestController annotation ? @Controller and @RestController are both annotations in Spring Boot, but they serve slightly different purposes: **@Controller:** ============================== - Indicates a class is a web request handler (e.g., a servlet). - Typically used for handling web requests and returning views (e.g., HTML pages). - Methods can return various types, including strings, views, and objects. - Does not automatically convert return values to JSON or other formats. **@RestController:** ============================== - A specialized version of @Controller for building RESTful web services. - Automatically converts return values to JSON or other formats (using HTTP message converters). - Methods can return objects, which are automatically serialized to JSON or other formats. - Implicitly assumes the handling of HTTP requests and respIn summary:mmary:** - **@Controller** is for handling web requests and returning views or other types of responses. - **@RestController** is specifically designed for building RESTful APIs and automatically converts return values to JSON or other formats. - When building a RESTful API, use @RestController to simplify the process and leverage automatic conversion features. - For handling web requests and returning views, use @Controller.

Full stack web development https://drive.google.com/drive/folders/1n_bVmiHFZVGBKP-6bI3hvuqytxoykh_Q 𝗖𝗼𝘃𝗲𝗿 𝗧𝗼𝗽𝗶𝗰𝘀 𝗶𝗻 𝘁𝗵𝗶𝘀 𝗗𝗿𝗶𝘃𝗲 ⬇️ ⏺ HTML ⏺ CSS ⏺ javascript ⏺ Bootstrap ⏺ JQuery ⏺ ReactJs ⏺ API (RESTFul api) Must open this drive and start learning (Jada idhar udhar mat bhagiye ikk chiz ko pakad kr usko complete kriye Phele) https://youtube.com/@codingdrawrun?si=PHs6nEU-AfOM6aIv

👨‍💻 Java Coding Challenge A. true B. false C. null ⬇️ Guess the code output in the comments!

🧑‍💻 Java Quiz What is the purpose of the toString() method in Java? A. To convert an object to a primitive data type. B. To compare two objects for equality. C. To return a string representation of an object. D. To throw an exception if an object is null. ⬇️ Guess the correct option in the comments!

============================== 𝐈𝐍𝐓𝐄𝐑𝐕𝐈𝐄𝐖 𝐐𝐔𝐄𝐒𝐓𝐈𝐎𝐍 ============================== Q. What is difference between Break and Continue in Java ? "Break" and "Continue" are both keywords in Java, used in loops and conditional statements. "Break" is used to: - Exit a loop or switch statement immediately - Stop executing the current block of code - Transfer control to the next statement after the loop or switch "Continue" is used to: - Skip the current iteration of a loop - Move to the next iteration of the loop - Only execute the next statement if the condition is true In other words: - "Break" says "Stop here and get out!" - "Continue" says "Skip this iteration and move to the next one!" ≠============================= LEARN 2MIN ONLY ==============================

👨‍💻 Java Quiz Which collection class in Java does not allow duplicates? A. ArrayList B. HashSet C. LinkedList ⬇️ Guess the correct option in the comments!

👨‍💻 Java Coding Challenge A. NPE B. 0 C. no output ⬇️ Guess the code output in the comments!

𝗤. 𝗪𝗵𝗮𝘁 𝗮𝗿𝗲 𝘁𝗵𝗲 𝗠𝗲𝗺𝗼𝗿𝘆 𝗔𝗹𝗹𝗼𝗰𝗮𝘁𝗶𝗼𝗻𝘀 𝗮𝘃𝗮𝗶𝗹𝗮𝗯𝗹𝗲 𝗶𝗻 𝗝𝗮𝘃𝗮𝗝𝗮𝘃𝗮? Java has five significant types of memory allocations. · Class Memory · Heap Memory · Stack Memory · Program Counter-Memory · Native Method Stack Memory 𝟭. 𝗖𝗹𝗮𝘀𝘀 𝗠𝗲𝗺𝗼𝗿𝘆 𝐖𝐡𝐚𝐭: Stores class-related data like methods and static variables. 𝐖𝐡𝐞𝐫𝐞: In Metaspace (Java 8+) or PermGen (pre-Java 8). 𝟮. 𝗛𝗲𝗮𝗽 𝗠𝗲𝗺𝗼𝗿𝘆 𝐖𝐡𝐚𝐭: Stores objects and instance variables. 𝐖𝐡𝐞𝐫𝐞: In the heap, divided into Young Generation and Old Generation. 𝟯. 𝗦𝘁𝗮𝗰𝗸 𝗠𝗲𝗺𝗼𝗿𝘆 𝐖𝐡𝐚𝐭: Stores local variables and method call information. 𝐖𝐡𝐞𝐫𝐞: Each thread has its own stack. 𝟰. 𝗣𝗿𝗼𝗴𝗿𝗮𝗺 𝗖𝗼𝘂𝗻𝘁𝗲𝗿 (𝗣𝗖) 𝗥𝗲𝗴𝗶𝘀𝘁𝗲𝗿 𝐖𝐡𝐚𝐭: Holds the address of the current JVM instruction. 𝐖𝐡𝐞𝐫𝐞: Each thread has its own PC register. 𝟱. 𝗡𝗮𝘁𝗶𝘃𝗲 𝗠𝗲𝘁𝗵𝗼𝗱 𝗦𝘁𝗮𝗰𝗸 𝐖𝐡𝐚𝐭: Used for executing native methods via JNI (Java Native Interface). 𝐖𝐡𝐞𝐫𝐞: Each thread has its own native method stack.

👨‍💻 Java Quiz Which method is used to start a thread execution in Java? A. run() B. start() C. execute() ⬇️ Guess the correct option in the comments!

👨‍💻 SQL Quiz Which SQL function is used to return the largest value from a set of values? A. MAX() B. BIGGEST() C. HIGHEST() ⬇️ Guess the correct option in the comments!

Part 1

𝐐. 𝐖𝐡𝐚𝐭 𝐢𝐬 𝐒𝐢𝐧𝐠𝐥𝐞𝐭𝐨𝐧 𝐜𝐥𝐚𝐬𝐬 𝐢𝐧 𝐉𝐚𝐯𝐚? A Singleton class in Java is a class that allows only one instance/Object of itself to be created and provides a way to access that instance/Object globally. (i.e only one time object created) 𝐲𝐨𝐮 𝐜𝐚𝐧 𝐜𝐫𝐞𝐚𝐭𝐞 𝐚 𝐒𝐢𝐧𝐠𝐥𝐞𝐭𝐨𝐧 𝐜𝐥𝐚𝐬𝐬 𝐛𝐲 𝐟𝐨𝐥𝐥𝐨𝐰𝐢𝐧𝐠 𝐭𝐡𝐞𝐬𝐞 𝐬𝐭𝐞𝐩𝐬: ⏺ Make the 𝐜𝐨𝐧𝐬𝐭𝐫𝐮𝐜𝐭𝐨𝐫 of the class private to prevent outside instantiation. ⏺ Create a private static instance/Object of the class within the class itself. ⏺ Provide a public static method that returns the instance of the class. If the instance is null, create a new instance; otherwise, return the existing one.

What is the difference between Java collection and Java collections? 𝗝𝗮𝘃𝗮 𝗖𝗼𝗹𝗹𝗲𝗰𝘁𝗶𝗼𝗻 ============================== 𝗗𝗲𝗳𝗶𝗻𝗶𝘁𝗶𝗼𝗻: Collection is an interface. 𝗜𝗻𝘁𝗿𝗼𝗱𝘂𝗰𝘁𝗶𝗼𝗻: Introduced in Java 1.2. 𝗣𝘂𝗿𝗽𝗼𝘀𝗲: Provides the framework for representing and manipulating groups of objects (like List, Set, Queue). Advantage (Collection): Standardizes the way groups of objects are handled. Java Collections Definition: Collections is a utility class. Introduction: Introduced in Java 1.2. Purpose: Provides static methods for sorting, searching, and modifying collections. Advantage (Collections): Offers utility methods to simplify common tasks on collections.