java synchronized

The synchronized keyword in Java is used to provide mutual exclusion and ensure that only one thread can access a shared resource at a time. When a method or block is marked as synchronized, it means that only one thread can execute it at a time, and other threads have to wait until the first thread is done executing.

The synchronized keyword can be used with methods, instance variables, and blocks of code. When used with a method or an instance variable, it synchronizes on the object instance that the method or variable belongs to. When used with a block of code, it synchronizes on a specified object.

Synchronization is important in multi-threaded environments to prevent race conditions and ensure data consistency. However, excessive use of synchronization can lead to performance issues, as threads may have to wait for each other to access shared resources. It's important to use synchronization judiciously and only when necessary.