What happens if an increment operation is performed on a variable in a multithreaded environment without synchronization mechanisms?

Performing an increment operation (for example, counter++ or counter += 1) on a variable in a multithreaded environment without synchronization can lead to a race condition. This is because the increment operation is not atomic — it consists of multiple steps (reading the value, increasing it, writing it back).

As a result:

• Multiple threads may read the same value simultaneously,
• Each will increment it locally,
• Write it back, overwriting each other's changes.

This can cause the final value of the variable to be less than expected, as some increments are "lost".

To prevent such errors in Java, synchronization mechanisms are used, such as:

• synchronized blocks or methods,
• Classes from java.util.concurrent.atomic (e.g., AtomicInteger),
• Other locking primitives (Lock).

Example with AtomicInteger:

import java.util.concurrent.atomic.AtomicInteger;

public class Counter {
    private AtomicInteger count = new AtomicInteger(0);

    public void increment() {
        count.incrementAndGet();
    }

    public int getCount() {
        return count.get();
    }
}