What is the essence of using ReadWriteLock?

ReadWriteLock allows multiple threads to read a shared resource simultaneously, but only one thread to write to it at a time. This improves performance in scenarios where reads are more frequent than writes.

Main components:

• Read Lock: Can be held by multiple threads simultaneously.
• Write Lock: Can only be held by one thread. It blocks both other writers and readers.

A similar behavior without ReadWriteLock would require using synchronized or ReentrantLock, which would block all operations (reading and writing) while any thread holds the lock.

Example usage:

import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

class SharedResource {
    private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
    private String data = "Initial Data";

    public String readData() {
        rwLock.readLock().lock(); // Acquire read lock
        try {
            // Read data
            return data;
        } finally {
            rwLock.readLock().unlock(); // Release read lock
        }
    }

    public void writeData(String newData) {
        rwLock.writeLock().lock(); // Acquire write lock
        try {
            // Write data
            this.data = newData;
        } finally {
            rwLock.writeLock().unlock(); // Release write lock
        }
    }
}