In Java, synchronization is a crucial concept used to control access to shared resources by multiple threads, ensuring thread safety and preventing issues such as data corruption and inconsistent states. The difference between a synchronized method and a synchronized block primarily lies in the scope and granularity of the lock that is applied.
Synchronized Method
A synchronized method automatically acquires a lock for the entire method upon entry by any thread, and releases it upon exit. This lock is either on the object (for instance methods) or on the class (for static methods). When a thread enters a synchronized method, no other thread can enter any other synchronized method on the same object (or class, in the case of static methods) until the first thread exits the method.
Scope of Lock: The lock is on the entire method, so no other synchronized method on the same object or class can be executed by another thread at the same time.
Ease of Use: Synchronized methods are easier to implement as the synchronization is handled automatically by the JVM when the method is declared with the synchronized keyword.
Performance: Since the entire method is locked, it can lead to reduced performance, especially if the method contains operations that do not require synchronization.
Synchronized Block
A synchronized block, on the other hand, allows more granular control over the synchronization process. It only locks a specific block of code within a method, rather than the entire method. The block is synchronized on a specific object, which can be any Java object, including this or any class object for static methods.
Scope of Lock: The lock is limited to the block of code specified within the synchronized block. Other parts of the method, or other methods on the same object, can be accessed by other threads while the block is locked.
