Java Collections Framework: Overview and Benefits

Immutable class in Java: What is immutable class? Its a class whose instances cannot be changed after creation. How to create an immutable class? 1️⃣declare class as `final` - Prevents other classes from extend it 2️⃣ declare fields as `private` and `final` - `private` prevents the fields cannot be accessed outside of the class; `final` assures the value will be set only once 3️⃣ no setter methods - Prevents overriding the values 4️⃣ constructor initialisation - Initialises all the fields in the all arguments consructor Here are some of the ways to create an immutable class(refer the image). 1️⃣ Using plain Java 2️⃣ Using lombok library - lombok provides `Value` annotation to create immutable class with minimal code 3️⃣ Using records - `public record User(int id, String name){}` Reference: https://lnkd.in/ghDmd4Ww Note: Lombok doesn't convert a collections like List, Set or Map to immutable internally. Make sure you're passing an immutable collections to the constructor. `Arrays.asList`, Factories like `List.of`, `Set.of`, and `Map.of` return immutable collection. `java.util.Collections` provides utility methods to convert the mutable connections to immutable. #java #lombok #immutable #LearnJava #programming

🚀 Variables & Constants in Java | Core Java Basics 💡 Variables and Constants are the building blocks of any Java program. Understanding them clearly helps you write clean, efficient, and bug-free code. 🔹 Variables in Java A variable is a container used to store data that can change during program execution. ✅ Types of Variables in Java: Local Variable – Declared inside a method Instance Variable – Declared inside a class (non-static) Static Variable – Shared across all objects of a class 📌 Example: int count = 10; 🔹 Constants in Java A constant is a variable whose value cannot be changed once assigned. ✅ Created using the final keyword 📌 Example: final double PI = 3.14159; 🔒 Constants improve: Code readability Safety Maintainability 🔍 Key Difference Variables Constants Value can change Value cannot change Flexible Fixed No final keyword Uses final keyword 🎯 Why This Matters? ✔ Strong foundation for OOP ✔ Avoids logical errors ✔ Frequently asked in Java interviews 📘 Learning Java step by step makes you a better developer. 🚀 Follow MD AZMAT RAZA for beginner-to-advanced Java & coding resources. #Java #CoreJava #JavaBasics #Programming #Coding #SoftwareEngineering #LearnJava

🔥 DAY 24 – JAVA LEARNING SERIES After collections, it’s time to understand how Java bridges primitive data types with objects. This concept is widely used in collections, frameworks, and interview questions. 💡💻 📘 Today’s Focus: Wrapper Classes in Java 🔹 Why wrapper classes are needed 🔹 List of wrapper classes in Java 🔹 Primitive data types vs Wrapper classes 🔹 Autoboxing and Unboxing 🔹 Wrapper classes usage in Collections 🔹 Common interview questions on wrapper classes 📝 Practice Questions for Day 24 1️⃣ Convert primitive data to wrapper object and vice versa 2️⃣ Demonstrate autoboxing and unboxing with example 3️⃣ Store primitive values in an ArrayList using wrapper classes 4️⃣ Compare == and .equals() with wrapper objects 5️⃣ Explain why collections cannot store primitive data Are wrapper classes clear now? Comment CLEAR or CONFUSED 👇 #Java #JavaLearning #CoreJava #WrapperClasses #JavaDeveloper #ProgrammingJourney #100DaysOfCode #InterviewPreparation #Collections #BackendDeveloper

📘 Java Basics Series | Topic: Methods in Java Today, I learned one of the most important concepts in Java — Methods 🚀 🔹 What is a Method? A method is a block of code that performs a specific task. It helps us reuse code, reduce repetition, and write clean programs. 🔹 Why Methods are Important? ✔ Code reusability ✔ Better readability ✔ Easy maintenance ✔ Structured programming 🔹 Types of Methods in Java 1️⃣ Method without parameters & without return value void greet() { System.out.println("Hello Java"); } 2️⃣ Method with parameters & without return value void add(int a, int b) { System.out.println(a + b); } 3️⃣ Method without parameters & with return value int getNumber() { return 10; } 4️⃣ Method with parameters & with return value int multiply(int a, int b) { return a * b; } 🔹 Static vs Non-Static Methods Static Method → Called using class name Non-Static Method → Called using object 💡 Key Takeaway: Methods make Java programs modular, reusable, and easy to understand. 📈 Learning Java step by step and enjoying the journey! #Java #JavaProgramming #MethodsInJava #CoreJava #LearningJava #ProgrammingBasics #DeveloperJourney

📘 Core Java Day 13 | Synthetic Classes in Java Today learned about synthetic classes a concept that exists in Java even though we never write it in our code. - Synthetic classes are not written by developers - They are generated automatically by the compiler / JVM - Their bytecode is added behind the scenes - They are not visible in Java source code - We cannot directly create or modify them Where are synthetic classes used? Arrays in Java - When we create an array, Java does not expose any constructor Still, an object is created on the heap - This is possible because arrays are instances of JVM-generated synthetic classes Inner class access - Synthetic classes and methods are used to allow inner classes to access private members of outer classes Why are synthetic classes needed? - To simplify Java syntax for developers - To hide low-level implementation details - To maintain performance and safety - To support language features without exposing complexity

🌱 Day 3 of Core Java Revision 🚀 📘 Java Collections Framework – Map & HashMap (Final Day) Wrapping up my Java Collections revision journey today by focusing on Map & HashMap, one of the most important and frequently used collections in backend development. Over these 3 days, I revised only the core, interview-relevant, and real-world collections that are used most often in Java applications. 🔍 Today’s focus: Map & HashMap • Stores data in key–value pairs • No duplicate keys allowed • Allows one null key and multiple null values • Unordered collection (no insertion order guarantee) • Not thread-safe by default 🛠 Hands-on practice with HashMap: • Creating HashMap using upcasting • Adding entries with put() • Checking map state (isEmpty(), size()) • Searching using containsKey() & containsValue() • Accessing values using get(key) • Removing entries using remove(key) • Retrieving: • Keys with keySet() • Values with values() • Iterating using entrySet() and for-each loop 💡 Key Reflection: Rather than covering every collection, I focused on most-used and interview-critical ones — List, Set, and Map. Strong fundamentals matter more than knowing everything. #Corejava #Map #HashMap #Coding

🔥 DAY 25 – JAVA LEARNING SERIES After wrapper classes, it’s time to work with the most frequently used class in Java applications. This topic is asked in almost every Java interview and used daily in real world projects. 💡💻 📘 Today’s Focus: String Handling in Java 🔹 What is String and why it is immutable 🔹 String pool and memory concept 🔹 Creating String using literal vs new keyword 🔹 String vs StringBuilder vs StringBuffer 🔹 Commonly used String methods 🔹 String related interview questions 📝 Practice Questions for Day 25 1️⃣ Check whether two Strings are equal using == and .equals() 2️⃣ Reverse a String using StringBuilder 3️⃣ Count vowels and consonants in a String 4️⃣ Check if a String is palindrome 5️⃣ Demonstrate immutability of String with an example Are Strings making sense now? Comment CLEAR or NEED PRACTICE 👇 #Java #JavaLearning #CoreJava #StringHandling #JavaDeveloper #ProgrammingJourney #100DaysOfCode #InterviewPreparation #CodingPractice #BackendDeveloper

🚀 Day 83 | Java Collections – TreeMap Today, I explored TreeMap, one of the most powerful implementations of the Map interface in Java. 🔹 What is TreeMap? TreeMap stores key–value pairs in a sorted order of keys. By default, it follows natural ordering, or you can define a custom Comparator. 🔹 Key Features ✅ Sorted Map (Ascending order by default) ✅ No duplicate keys ✅ Allows null values, but not null keys ✅ Based on Red-Black Tree (Self-balancing BST) ✅ Provides efficient range-based operations 🔹 Commonly Used Methods put() – Insert key-value pairs get() – Retrieve value by key firstKey() / lastKey() – Access boundary keys higherKey() / lowerKey() – Navigation methods subMap() / headMap() / tailMap() – Range views 🔹 When to Use TreeMap? When sorted data is required When range queries are important When ordered traversal matters more than speed 📌 Note: TreeMap is slightly slower than HashMap due to sorting, but extremely useful when order matters. 💡 Learning Outcome Understanding TreeMap helps in writing cleaner, more efficient code when working with sorted key-value data. 📚 Consistent learning + practice = mastery #Day83 #Java #TreeMap #CollectionsFramework #DSA #LearningInPublic #LinkedInDaily #SoftwareDeveloper

Why do some Java fields remain accessible across packages, while others fail even inside subclasses? And how does Java actually enforce access rules at compile time? In this blog, we will explore Java access modifiers by placing the same code in different contexts and observing how Java responds. Instead of explaining rules upfront, the article walks through scenarios such as access within the same class, from another class in the same package, from subclasses, and across different packages. Each access modifier—public, private, protected, and default—is demonstrated using focused code examples that clearly show what compiles and what doesn’t. The goal is to make access control something you can reason about by reading and running code, rather than something you memorize from a table. #Java #AccessModifiers #JavaProgramming #OOP #Programming #SoftwareEngineering https://lnkd.in/gJE58itQ

Post 1: Multithreading and Concurrency in Java Concept: Multithreading allows multiple threads to run simultaneously within a single process, while concurrency manages multiple tasks making progress at the same time. Why it matters: Multithreading improves performance, responsiveness, and resource utilization, especially in real-time systems, servers, and applications handling multiple users. Example / Snippet: class MyThread extends Thread { public void run() { System.out.println("Thread running"); } } Takeaway: Multithreading enables faster and more efficient program execution. Post 2: Thread Class and Runnable Interface Concept: Java provides two main ways to create threads: Thread class → extend the Thread class Runnable interface → implement Runnable and pass it to a Thread Why it matters: Using Runnable supports better design and allows class inheritance, making code more flexible and reusable. Example / Snippet: class Task implements Runnable { public void run() { System.out.println("Runnable thread"); } } new Thread(new Task()).start(); Takeaway: Prefer Runnable for better object-oriented design. Post 3: Thread Lifecycle Concept: A thread passes through multiple states: New → Runnable → Running → Waiting/Blocked → Terminated Why it matters: Understanding thread states helps in debugging and performance tuning of concurrent applications. Example / Snippet: Thread t = new Thread(); System.out.println(t.getState()); Takeaway: Thread lifecycle explains how threads behave during execution. Post 4: Thread Methods (sleep, join, interrupt) Concept: sleep() → pauses thread for a given time join() → waits for another thread to finish interrupt() → interrupts a sleeping or waiting thread Why it matters: These methods help in controlling thread execution and coordination. Example / Snippet: Thread.sleep(1000); t.join(); t.interrupt(); Takeaway: Thread methods manage execution timing and flow. #Java #CoreJava #Multithreading #Concurrency #Thread #Synchronization #ExecutorService #JavaDeveloper #LearnJava #CodingInJava #SoftwareDevelopment #TechLearning