Miks tekiliste võistlused tekivad ja kuidas sellega…

Race conditions occur when multiple threads simultaneously access shared mutable data, and the final result depends on the order of execution. The problem is that the thread scheduler can switch threads at any moment, and an operation on data that appears atomic in code can be interrupted and executed in parts by other threads.

Combating race conditions involves ensuring correct access to shared resources. Main methods:

Synchronization: Restricts concurrent access to critical sections of code where shared data is used. Popular mechanisms:

synchronized keyword: provides locking at the object or class level.

// Object-level lock
synchronized (this) {
    // Critical section
    sharedData++;
}

// Class-level lock
synchronized (MyClass.class) {
    // Critical section
    sharedStaticData++;
}

Explicit locks (Lock interface, ReentrantLock): offer more flexibility, such as trying to acquire a lock or acquiring it with a timeout.

Lock lock = new ReentrantLock();
// ...
lock.lock(); // Acquire lock
try {
    // Critical section
    sharedData++;
} finally {
    lock.unlock(); // Release lock (must be in finally)
}

Atomic operations: Using classes from the java.util.concurrent.atomic package, which provide atomic operations (e.g., increment, compare-and-swap) without explicit thread locking.
```
import java.util.concurrent.atomic.AtomicInteger;

AtomicInteger atomicCounter = new AtomicInteger(0);
// ...
atomicCounter.incrementAndGet(); // Atomic increment
```
Thread-safe collections: Using collections from the java.util.concurrent package (e.g., ConcurrentHashMap, CopyOnWriteArrayList) designed for concurrent environments.
Immutable data: If data cannot be changed after creation, multiple access to it will not cause race conditions.
Thread-local storage: Each thread has its own copy of variables, eliminating shared access issues.

The choice depends on the specific situation and the required level of synchronization. Excessive synchronization can lead to significant overhead and even deadlocks.

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