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This article explains the principles, advantages, and drawbacks of CAS, LongAdder, and AtomicLong in Java, illustrating why Alibaba recommends LongAdder for high‑concurrency counter scenarios, how the ABA problem arises, and how AtomicStampedReference can mitigate it.
This article explains the principles, advantages, and drawbacks of Java's AtomicLong and LongAdder counters, describes the CAS operation and its ABA problem, and analyzes why Alibaba recommends LongAdder for high‑concurrency, high‑availability scenarios in distributed systems.
In high‑concurrency Java applications, LongAdder—introduced in JDK 8 and using partitioned cells to reduce contention—generally outperforms the single‑value AtomicLong, which relies on CAS and can cause CPU waste under heavy load, so Alibaba advises LongAdder for scalable distributed counters, though memory usage and workload specifics must be considered.
This article introduces Java's java.util.concurrent.atomic package, detailing the core atomic classes—AtomicBoolean, AtomicInteger, AtomicLong, and LongAdder—including their constructors, key methods, typical use cases, and performance considerations in high‑concurrency scenarios for developers seeking efficient thread‑safe operations.
This article explains why LongAdder was introduced to overcome AtomicLong's CAS contention bottleneck, explores the design of Striped64 and its cells, and walks through key source code snippets of LongAdder, DoubleAdder, and the longAccumulate method, highlighting concurrency mechanisms and performance considerations.
This article explains how to write a concurrent unit test for the AssetService.update method using thread pools, CountDownLatch, AtomicInteger, and then suggests optimizations such as replacing AtomicInteger with LongAdder and employing CyclicBarrier to increase contention, providing full code examples and detailed explanations.
This article examines the thread‑safety of the volatile keyword under multi‑write scenarios, demonstrates its failure with a concurrent counter test, and benchmarks LongAdder against AtomicInteger using JMH, revealing LongAdder’s superior performance under high contention and AtomicInteger’s advantage in low‑contention environments.
This article explains the evolution and implementation of Java's JVM‑level locks—including synchronized, ReentrantLock, ReentrantReadWriteLock, and LongAdder—detailing their lock‑upgrade process, internal object layout, AQS‑based algorithms, and how they improve concurrency and performance in multithreaded applications.