The implementation part was fine, wrapping the methods with synchronized wasn't hard.
Start by writing a simple synchronized counter class with increment, decrement, and get methods, then explain how synchronized provides mutual exclusion and memory visibility. Next, compare it to AtomicInteger, highlighting that synchronized uses blocking locks while AtomicInteger uses lock-free CAS, and discuss performance trade-offs under different contention levels.
Pro tip: Mention that under low contention, synchronized can be faster due to JVM optimizations like biased locking, but under high contention, AtomicInteger's CAS avoids context switching and scales better. Also note that AtomicInteger's get() is not synchronized and may return stale values, which is acceptable for many use cases.
Write a class with a private int value and synchronized methods for increment, decrement, and get. Explain that synchronized ensures atomicity and visibility.
Describe how synchronized uses monitor locks, causing thread blocking and context switching under contention, and how it guarantees happens-before relationships.
Explain that AtomicInteger uses CAS (compare-and-swap) operations, which are lock-free and non-blocking, allowing threads to retry without being suspended.
Analyze lock contention vs CAS: synchronized may be faster under low contention due to JVM optimizations, but under high contention, CAS avoids context switching and scales better, though it can suffer from ABA problem and high retry overhead.
Conclude that for simple counters, AtomicInteger is generally preferred for scalability, but synchronized is simpler and may be sufficient for low-contention scenarios.
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