Concurrency

Learn

Existing chapters for this concept.

• Concurrency

  Concurrency

  Millions of cheap threads for blocking I/O . Don't pool them like platform threads.

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See it in code

Existing Java examples.

• advconcurrency 1 Count Down Latch

  Advanced concurrency · pkg16advconcurrency/advconcurrency1CountDownLatch.java · pkg16advconcurrency · advconcurrency1CountDownLatch.java

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• advconcurrency 2 Cyclic Barrier

  Advanced concurrency · pkg16advconcurrency/advconcurrency2CyclicBarrier.java · pkg16advconcurrency · advconcurrency2CyclicBarrier.java

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• advconcurrency 3 Semaphore

  Advanced concurrency · pkg16advconcurrency/advconcurrency3Semaphore.java · pkg16advconcurrency · advconcurrency3Semaphore.java

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• advconcurrency 4 Phaser

  Advanced concurrency · pkg16advconcurrency/advconcurrency4Phaser.java · pkg16advconcurrency · advconcurrency4Phaser.java

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• advconcurrency 5 Exchanger

  Advanced concurrency · pkg16advconcurrency/advconcurrency5Exchanger.java · pkg16advconcurrency · advconcurrency5Exchanger.java

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• advconcurrency 6 Java Memory Model

  Advanced concurrency · pkg16advconcurrency/advconcurrency6JavaMemoryModel.java · pkg16advconcurrency · advconcurrency6JavaMemoryModel.java

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• advconcurrency 7 Structured Concurrency

  Advanced concurrency · pkg16advconcurrency/advconcurrency7StructuredConcurrency.java · pkg16advconcurrency · advconcurrency7StructuredConcurrency.java

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• concurrency 1 Thread Basics

  Concurrency · pkg7concurrency/concurrency1ThreadBasics.java · pkg7concurrency · concurrency1ThreadBasics.java

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• concurrency 2 Synchronization Demo

  Concurrency · pkg7concurrency/concurrency2SynchronizationDemo.java · pkg7concurrency · concurrency2SynchronizationDemo.java

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• concurrency 3 Executors Demo

  Concurrency · pkg7concurrency/concurrency3ExecutorsDemo.java · pkg7concurrency · concurrency3ExecutorsDemo.java

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• concurrency 4 Completable Future Demo

  Concurrency · pkg7concurrency/concurrency4CompletableFutureDemo.java · pkg7concurrency · concurrency4CompletableFutureDemo.java

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• concurrency 5 Fork Join Demo

  Concurrency · pkg7concurrency/concurrency5ForkJoinDemo.java · pkg7concurrency · concurrency5ForkJoinDemo.java

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• concurrency 6 Virtual Threads Demo

  Concurrency · pkg7concurrency/concurrency6VirtualThreadsDemo.java · pkg7concurrency · concurrency6VirtualThreadsDemo.java

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• concurrency 7 Producer Consumer

  Concurrency · pkg7concurrency/concurrency7ProducerConsumer.java · pkg7concurrency · concurrency7ProducerConsumer.java

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• concurrency 8 Locks And Coordination

  Concurrency · pkg7concurrency/concurrency8LocksAndCoordination.java · pkg7concurrency · concurrency8LocksAndCoordination.java

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Reference

• Java Memory Model (pkg16advconcurrency)

  Reference

  Deep concurrency beyond threads — synchronizers, visibility, structured concurrency.

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Prepare

Existing interview questions.

• How does ConcurrentHashMap achieve concurrency?

  Collections Framework — Interview Questions (120+)

  Bucket-level CAS + synchronized bins; no global lock.

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• Concurrency & Multithreading — Interview Questions (150+)

  Concurrency & Multithreading — Interview Questions (150+)

  Prefer immutability and high-level concurrency utilities over low-level locks.

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• structured concurrency preview?

  Java 9–21 Features — Interview Questions (95+)

  infers raw-ish; specify generic.

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• Optimistic concurrency?

  System Design Fundamentals — Interview Questions (80+)

  Start simple; scale the proven bottleneck; justify trade-offs.

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Java versions

• More Concurrency Updates

  JEP 266 · Final

  More Concurrency Updates. java.util.concurrent.Flow publishes the reactive-streams interfaces. CompletableFuture also gains more composition methods.

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• Structured Concurrency (Incubator)

  JEP 428 · Incubator

  Structured Concurrency (Incubator). An incubator API treats related tasks as one unit of work. It is not a preview feature and not a standard API.

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• Structured Concurrency (Second Incubator)

  JEP 437 · Incubator

  Structured Concurrency (Second Incubator). Structured concurrency incubates a second time. It is still not a preview.

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• Java 21

  JSR 396 · long-term support

  JDK 21, JSR 396, reached general availability on 19 September 2023. Virtual threads, record patterns, switch patterns, and sequenced collections are final.…

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• Structured Concurrency (Preview)

  JEP 453 · Preview

  Structured Concurrency (Preview). Structured concurrency is a preview API. Related tasks form one unit of work that can cancel and report errors together.

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• Structured Concurrency (Second Preview)

  JEP 462 · Preview

  Structured Concurrency (Second Preview). Structured concurrency is previewed a second time.

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• Structured Concurrency (Third Preview)

  JEP 480 · Preview

  Structured Concurrency (Third Preview). Structured concurrency is previewed a third time.

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• Structured Concurrency (Fourth Preview)

  JEP 499 · Preview

  Structured Concurrency (Fourth Preview). Structured concurrency is previewed a fourth time.

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• Java 25

  JSR 400 · long-term support

  JDK 25, JSR 400, reached general availability on 16 September 2025. Final, preview, incubator, and experimental JEPs stay in those statuses, including JEP 509…

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• Structured Concurrency (Fifth Preview)

  JEP 505 · Preview

  Structured Concurrency (Fifth Preview). A preview API treats related tasks in different threads as one unit of work, so cancellation and errors stay with that…

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