Java Multithreading Basics: Understanding Threads and Synchronization

🧵 Multithreading Today I explored some important concepts of Multithreading in Java. Multithreading allows a program to execute multiple tasks simultaneously, improving performance and efficient CPU utilization. 🔹 Two Ways to Achieve Multitasking • Process-based multitasking – Multiple programs run simultaneously. • Thread-based multitasking – Multiple threads run inside a single program. 🔹 Two Ways to Create Threads 1️⃣ Extending Thread Class – Create a class that extends Thread and override the run() method. 2️⃣ Implementing Runnable Interface – Create a class that implements Runnable and pass it to a Thread object. 🔹 Important Thread Control Methods • Thread.sleep(milliseconds) – Pauses the current thread for a specific time. • Object.wait() – Makes the thread wait until another thread notifies it. • Thread.join() – Makes a thread wait until another thread finishes execution. • Thread.yield() – Temporarily pauses the current thread to allow other threads of the same priority to execute. • Thread.suspend() – Temporarily stops a thread (⚠ Deprecated in Java). 🔹 Synchronization Synchronization is used to control the access of multiple threads to shared resources and prevent data inconsistency. 💡 Understanding multithreading concepts helps build efficient and high-performance Java applications. #Java #Multithreading #JavaProgramming #LearningJava #CodingJourney #SoftwareDevelopment

♻️ Ever wondered how Java manages memory automatically? Java uses Garbage Collection (GC) to clean up unused objects — so developers don’t have to manually manage memory. Here’s the core idea in simple terms 👇 🧠 Java works on reachability It starts from GC Roots: • Variables in use • Static data • Running threads Then checks: ✅ Reachable → stays in memory ❌ Not reachable → gets removed 💡 Even objects referencing each other can be cleaned if nothing is using them. 🔍 Different types of Garbage Collectors in Java: 1️⃣ Serial GC • Single-threaded • Best for small applications 2️⃣ Parallel GC • Uses multiple threads • Focuses on high throughput 3️⃣ CMS (Concurrent Mark Sweep) • Runs alongside application • Reduces pause time (now deprecated) 4️⃣ G1 (Garbage First) • Splits heap into regions • Balanced performance + low pause time 5️⃣ ZGC • Ultra-low latency GC • Designed for large-scale applications ⚠️ One important thing: If an object is still referenced (even accidentally), it won’t be cleaned → which can lead to memory issues. 📌 In short: Java automatically removes unused objects by checking whether they are still reachable — using different GC strategies optimized for performance and latency. #Java #Programming #JVM #GarbageCollection #SoftwareDevelopment #TechConcepts

📘 Abstract Class vs Interface in Java — Key Differences Today I explored one of the most important OOP concepts in Java: the difference between Abstract Classes and Interfaces. Both are used to achieve abstraction, but they serve different design purposes in Java applications. 🔹 Abstract Class • Supports partial abstraction • Can contain both abstract and concrete methods • Allows instance variables and constructors • Supports single inheritance using extends 🔹 Interface • Used for full abstraction (mostly) • Methods are public and abstract by default • Variables are public static final • Supports multiple inheritance using implements 💡 Key takeaway: Abstract classes are used when classes share common behavior, while interfaces define a contract that multiple unrelated classes can implement. Understanding when to use each helps in writing clean, scalable, and maintainable Java code. A special thanks to my mentor kshitij kenganavar sir for clearly explaining the concepts of Abstract Classes and Interfaces in Java. #Java #OOP #JavaProgramming #AbstractClass #Interface #SoftwareDevelopm

🚀 Day 3/100 – Java Practice Challenge Continuing my #100DaysOfCode journey with another important core Java concept. 🔹 Topics Covered: Generics in Java Understanding type safety, reusability, and avoiding runtime errors. 💻 Practice Code: 🔸 Generic Class Example class Box { private T value; public void set(T value) { this.value = value; } public T get() { return value; } } 🔸 Usage Box intBox = new Box<>(); intBox.set(10); Box strBox = new Box<>(); strBox.set("Hello"); System.out.println(intBox.get()); // 10 System.out.println(strBox.get()); // Hello 📌 Key Learning: ✔ Generics provide compile-time type safety ✔ Avoid ClassCastException ✔ Help write reusable and clean code ⚠️ Important: • Use <?> for unknown types (wildcards) • Use for bounded types • Generics work only with objects, not primitives 🔥 Interview Insight: Generics use type erasure — type information is removed at runtime Widely used in collections like List, Map<K, V> 👉 Without Generics: List list = new ArrayList(); list.add("Java"); list.add(10); // No compile-time error ❌ #100DaysOfCode #Java #JavaDeveloper #Generics #CodingJourney #LearningInPublic #Programming

🧠Stack vs Heap Memory in Java - Every Developer Should Know This When learning java, understanding Stack and Heap memory makes debugging and writing efficient code much easier. 💠 Stack Memory Stack memory is used for temporary, method-specific data like local variables and method calls, and is managed automatically in a fast, Last-In, First-Out (LIFO) manner. ->Stores methods calls and local variables ->Memory is allocated and deallocated automatically ->Very fast access ->Each thread has its own stack 🧪 Example: int x = 10; 💠 Heap Memory Heap memory is used for storing all objects and instance variables, has a longer lifespan, and is managed by the Garbage Collector. -> Stores objects and instance variables ->Shared across threads ->Managed by the Garbage Collector ->Slightly slower than the stack memory 🧪 Example: User user = new User(); ⚡ Simple way to remember Stack ->Execution & temporary data Heap ->Objects & long-lived data Understanding this concept helps us to reason about memory management, performance and Garbage collection. #Java #JavaDeveloper #Programming #SoftwareEngineering #BackendDevelopment #LearningInPublic

In Java versions below 24 virtual threads can pin their carrier platform threads during synchronized blocks or native calls. This prevents the carrier from executing other tasks leading to thread starvation and sub-optimal resource usage. Interesting article on differences between Java 21 and Java 24 in terms how they handle virtual thread pinning. https://lnkd.in/dPpsDYHH

I recently explored a subtle but important concept in Java constructor execution order. Many developers assume constructors simply initialize values, but the actual lifecycle is more complex. In this article, I explain: • The real order of object creation • Why overridden methods can behave unexpectedly • A common bug caused by partial initialization This concept is especially useful for interviews and writing safer object-oriented code. Medium Link: https://lnkd.in/gtRhpdfP #Java #OOP #SoftwareDevelopment #Programming

Method Overloading in Java -> more than just same method names Method overloading allows a class to have multiple methods with the same name but different parameter lists. Java decides which method to call based on the method signature, which includes: • Number of parameters • Type of parameters • Order of parameters One important detail many people miss: Changing only the return type does not create method overloading. Why does this concept matter? Because it improves code readability and flexibility. Instead of creating different method names for similar operations, we can keep the same method name and let Java decide the correct one during compile time. That’s why method overloading is also called compile-time polymorphism. Small concepts like this form the foundation of how Java’s Object-Oriented Programming model really works. #Java #JavaProgramming #OOP #BackendDevelopment #CSFundamentals

The Diamond Problem in Java occurs in languages that allow multiple inheritance, where a class inherits from two classes that share a common superclass. This situation leads to ambiguity when both parent classes define the same method, raising the question of which method should be used. Java circumvents this issue by not supporting multiple inheritance with classes. However, a similar problem can arise with interfaces and default methods. Consider the following example: interface A { default void show() { System.out.println("A"); } } interface B { default void show() { System.out.println("B"); } } class Test implements A, B { public static void main(String[] args) { Test t = new Test(); t.show(); // This results in a compilation error } } In this case, since both interfaces provide the same method, Java requires the class to override it explicitly. Here’s how to resolve it with specific interface calls: class Test implements A, B { public void show() { A.super.show(); // Calls method from interface A B.super.show(); // Calls method from interface B } } This approach allows for explicit selection or combination of behavior from both interfaces. #Java #OOP #InterviewQuestions #BackendDevelopment #Programming

Blog: Some Benefits of Enabling Compact Object Headers in Java 25 for Streams There are signs. You just have to learn how to look for and read them. https://lnkd.in/e4ARCGbQ