Prevent race conditions and ensure thread safety when accessing shared data.
When multiple threads have access to shared, mutable state (like a common object or variable), you can run into concurrency problems. A race condition occurs when the outcome of a computation depends on the unpredictable timing or interleaving of operations from multiple threads. For example, if two threads try to increment a shared counter simultaneously, one of the increments might be lost. To prevent such issues and ensure data consistency, Java provides the `synchronized` keyword. Synchronization works by establishing locks on objects. When a thread enters a `synchronized` method or block, it acquires the intrinsic lock for that object (or the class object for static methods). While the thread holds the lock, no other thread can enter any `synchronized` block or method for the same object. Other threads attempting to acquire the lock will be blocked until the first thread exits the `synchronized` code and releases the lock. You can apply the `synchronized` keyword to an entire method, which locks on the `this` object for instance methods. Alternatively, you can use a `synchronized` block to lock on a specific object and protect only a critical section of code, which can be more efficient as it reduces the scope of the lock. While `synchronized` is a powerful tool for achieving thread safety, it's important to use it judiciously, as overuse can lead to performance bottlenecks and potential deadlocks, a situation where two or more threads are blocked forever, waiting for each other to release locks.