What approaches and methods prevent problems when multiple threads work simultaneously with a shared resource?

The following approaches are used to prevent problems when multiple threads work simultaneously with a shared resource:

• Synchronization using locks: using synchronized in Java, ReentrantLock, or other mechanisms to ensure mutual exclusion.

• Using atomic operations: classes from the java.util.concurrent.atomic package allow performing operations on variables atomically without locks.

• Using thread-safe collections: for example, ConcurrentHashMap, CopyOnWriteArrayList.

• Avoiding shared state: designing so that threads do not share mutable data.

• Using high-level constructs from java.util.concurrent: for example, semaphores, barriers, blocking queues.

Example using synchronized:

public class Counter {
    private int count = 0;

    public synchronized void increment() {
        count++;
    }

    public synchronized int getCount() {
        return count;
    }
}

Here, the methods increment and getCount are protected from concurrent access by multiple threads, preventing race conditions.