Java.Multithreading.Why do we need Synchronized (this) and Synchronized method if they give us the same result ?

Let’s unpack it carefully — the short answer is: ✅ they behave the same, but 🚀 give you flexibility in different contexts.

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🧠 The Core Truth

synchronized void foo()	Locks on this monitor
synchronized (this) { ... }	Also locks on this monitor

✅ So yes, they are functionally equivalent, but here’s why both exist and are useful:

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🔍 Difference in Control and Flexibility

🔹 synchronized(this)

public void foo() {
    synchronized (this) {
        // critical section
    }
}

✅ Gives you partial synchronization — only part of the method is locked

✅ You can synchronize on other objects too:

synchronized (someOtherObject) { ... }

✅ Can mix synchronized and unsynchronized logic:

public void update() {
    validateInputs();
    synchronized (this) {
        doCriticalUpdate();
    }
}

🔸 synchronized method

public synchronized void foo() {
    // critical section
}

✅ Cleaner and simpler syntax

✅ You can use it when the entire method is critical

❌ But you cannot control which object it synchronizes on — always this

✨ Summary: When to Use What?

Use Case	Prefer
Entire method is critical	✅ synchronized method
Only part of the method is critical	✅ synchronized(this) block
Want to lock on a different object	✅ synchronized(obj)
Need more advanced locking behavior	❗ Use ReentrantLock, not synchronized

🧪 Want an Example?

🔄 Mixed access method:

public class Counter {
    private int count = 0;

    public void increment() {
        // unsynchronized logic
        System.out.println("Pre-check done by " + Thread.currentThread().getName());

        // only this part is critical
        synchronized (this) {
            count++;
        }
    }
}

This would not be possible with a synchronized method.

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🚀 TL;DR

Concept	synchronized method	synchronized(this)
Lock target	this	this or any object
Control scope	Entire method	Any code block
Flexibility	❌ Less	✅ More
Readability	✅ Simpler	🟡 Slightly more verbose