What mechanisms ensure safe variable updates when working with multiple threads: volatile, atomics, or synchronized blocks?

In a multithreaded environment in Android (Java/Kotlin), different mechanisms are used for safe variable updates:

• volatile guarantees visibility of variable changes between threads but does not ensure atomicity of operations. That is, if the operation is complex (e.g., increment), volatile will not protect against race conditions.

• Atomic classes (AtomicInteger, AtomicBoolean, etc.) provide atomic operations on variables, allowing safe modifications without locks.

• Synchronized blocks ensure mutual exclusion, allowing only one thread to execute the critical section of code at a time. This is the most reliable way to protect complex operations but may impact performance.

The choice depends on the task:

• For simple read/write, volatile is suitable.
• For atomic operations, it's better to use atomic classes.
• For complex sequences of actions — synchronized.

Example with AtomicInteger:

import java.util.concurrent.atomic.AtomicInteger;

AtomicInteger counter = new AtomicInteger(0);
counter.incrementAndGet(); // atomic increment