On what fundamental principle is the non-blocking implementation of the AtomicInteger class based?

The non-blocking implementation of the AtomicInteger class in Java is based on the CAS (Compare-And-Swap) principle — an atomic operation of comparing and replacing a value. This operation allows updating the variable's value only if it has not changed since the last check, ensuring thread safety without using locks.

An example of using CAS in a simplified form:

import java.util.concurrent.atomic.AtomicInteger;

AtomicInteger atomicInt = new AtomicInteger(0);

// Attempt to increment the value by 1
int oldValue, newValue;
do {
    oldValue = atomicInt.get();
    newValue = oldValue + 1;
} while (!atomicInt.compareAndSet(oldValue, newValue));

Thus, AtomicInteger provides efficient synchronization between threads without the overhead of locking.