Introduction

A synchronized block is not always better than a synchronized method, but it gives you more control. The main advantage is precision: you can lock a smaller section of code, choose a specific lock object, and reduce unnecessary contention when the whole method does not need protection.

The Difference in Scope

A synchronized method locks for the entire method body:

1public synchronized void update() {
2    prepare();
3    criticalWrite();
4    cleanup();
5}

A synchronized block lets you protect only the part that is actually shared-state sensitive:

1public void update() {
2    prepare();
3    synchronized (this) {
4        criticalWrite();
5    }
6    cleanup();
7}

If prepare and cleanup do not touch shared mutable state, locking them adds unnecessary serialization.

Finer-Grained Locking Improves Concurrency

The biggest reason blocks are often preferred is that smaller lock scope usually means better throughput under contention.

If multiple threads can run the non-critical parts at the same time, the application wastes less time waiting for a monitor it does not actually need.

This is especially useful when the synchronized region is tiny compared with the total method body.

You Can Lock on a Different Object

With a synchronized method, the lock is fixed:

• instance method uses this
• static synchronized method uses the Class object

With a synchronized block, you can choose a dedicated lock object:

1public class Counter {
2    private final Object lock = new Object();
3    private int value = 0;
4
5    public void increment() {
6        synchronized (lock) {
7            value++;
8        }
9    }
10}

That is often safer than exposing your object's intrinsic lock to unrelated code paths.

Separate Locks for Separate Resources

Blocks also let you create independent locks for independent state.

1public class Stats {
2    private final Object userLock = new Object();
3    private final Object configLock = new Object();
4
5    private int userCount;
6    private int configVersion;
7
8    public void updateUserCount() {
9        synchronized (userLock) {
10            userCount++;
11        }
12    }
13
14    public void updateConfig() {
15        synchronized (configLock) {
16            configVersion++;
17        }
18    }
19}

If you synchronized both methods on this, unrelated operations would block each other for no good reason.

When a Synchronized Method Is Fine

There are still cases where a synchronized method is the right choice:

• the whole method truly is one critical section
• the class is small and clarity matters more than flexibility
• there is one obvious lock and one shared state boundary

In those cases, the method form is simpler and easier to read.

Prefer the Simplest Correct Locking Strategy

The real engineering rule is not "blocks are always better." It is:

• use the simplest synchronization mechanism that matches the real contention boundary

If the boundary is the full method, use a synchronized method. If only part of the method or part of the state is shared, a block is usually the better fit.

Common Pitfalls

The biggest mistake is synchronizing an entire method when only a few lines need protection. That increases contention and can hurt throughput.

Another issue is locking on this or a publicly reachable object when a private lock object would provide cleaner encapsulation.

A third problem is overcomplicating simple code with many tiny lock blocks when the whole method is genuinely one atomic operation.

Summary

• A synchronized block is often better because it gives finer control over lock scope.
• Blocks can reduce contention by locking only the truly critical section.
• They also let you choose dedicated lock objects instead of always locking on this.
• Synchronized methods are still fine when the entire method is one critical region.
• Prefer the locking strategy that matches the actual shared-state boundary.