Why Does `Thread.wait()` Throw `IllegalMonitorStateException`, and How Can I Fix It?

Thread Synchronization with wait() and IllegalMonitorStateException

When implementing multi-threading in Java, you may encounter the java.lang.IllegalMonitorStateException exception when using Thread.wait(). This issue arises when a thread attempts to call wait() without first acquiring the lock on the object it intends to wait on.

To rectify this situation and ensure proper thread synchronization, you must enclose the wait() call within a synchronized block of code for the object you wish to wait on:

synchronized (object) {
    object.wait();
}

In this block, the current thread acquires the lock on the specified object (object), allowing it to wait until notified without throwing the IllegalMonitorStateException.

An alternative solution is to leverage Java's concurrency packages, which provide a safer and more user-friendly approach to thread management. Consider utilizing the ConcurrentHashMap class or the Lock interface for improved synchronization and performance.

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