#45 | Synchronized method and Synchronized block | Java Interview

In this video, we explain the difference between a synchronized method and a synchronized block in Java — a very important Core Java & Multithreading interview question that also tests your understanding of performance and locking granularity. Most developers know synchronization, but interviews check whether you know where to synchronize and why. 👨‍💻 What you’ll learn: Synchronized Method • Locks the entire method • Uses the current object’s lock (this) • For static methods, uses the class-level lock • Only one thread can execute any synchronized method on the same object • Even non-critical code becomes single-threaded ⚠️ Downside: • Poor performance if the method has non-critical work • Threads wait unnecessarily Synchronized Block • Locks only a specific section of code • You can choose which object to lock • Better control and flexibility • Improves performance by locking only the critical section Common lock objects: • this • A dedicated lock object • ClassName.class (for static synchronization) Key Differences (Interview Gold) • Lock Scope: Method vs specific code block • Performance: Synchronized block is faster • Flexibility: Block allows custom locks • Granularity: Block = fine-grained locking Real-World Example Explained Scenario: • Two threads download files (independent work) • Both update a shared counter (critical section) Synchronized Method (BAD) • Entire download method is locked • Threads download one after another • Total time ≈ 4 seconds Synchronized Block (GOOD) • Only counter update is synchronized • Downloads run in parallel • Total time ≈ 2 seconds 👉 Same logic, half the time — this is why synchronized blocks are preferred. 🎯 What interviewers expect: • You understand monitor locks • You know performance tradeoffs • You can explain why synchronized block is better • You can give a real-world example 🧠 How you should answer in interviews: A synchronized method locks the entire method, making even non-critical code single-threaded. A synchronized block locks only the critical section and allows better performance by reducing lock scope. That’s why synchronized blocks are preferred in real applications. This video is perfect for Core Java interviews, multithreading fundamentals, backend preparation, and JVM concurrency concepts. 👉 Like, share & subscribe for more Java + backend engineering deep dives! #Java #Synchronization #Multithreading #Concurrency #SynchronizedBlock #CoreJava #JavaInterview #Performance #BackendEngineering #TechExplained