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‎.gitignore

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/target
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/deploy
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/.project
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/.classpath
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/.settings

‎README.md

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Java concurrency 예제
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=========
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## 예제 출처
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- [Effective Java 2nd edition](http://www.yes24.com/24/goods/2416238)
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- package: ej2
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- 원본 : <http://java.sun.com/docs/books/effective/effective2.zip>
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- [Java concurrency in practice](http://www.yes24.com/24/goods/1550580)
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- package : net.jcip
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- 원본 : <http://jcip.net/listings.html>, <http://jcip.net/jcip-examples-src.jar>
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- [Java 언어로 배우는 디자인 패턴 입문 멀티 쓰레드 편](http://www.yes24.com/24/goods/2922297)
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- package : jdm
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- 원본 : <http://ndisk.youngjin.com/bookcd/pds_view.asp?pcd=9788931436921>
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- [유쾌한 자바 퍼즐러](http://www.yes24.com/24/Goods/2600965)
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- 원본 : <http://www.javapuzzlers.com/java-puzzlers.zip>
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- package : jpz
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- [Concurrent Programming Distributed Applications 발표](http://www.infoq.com/presentations/Concurrent-Distributed-Applications-Spring
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)
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- SpringOne 2GX 2010에서 David Syer와 Mark Fisher가 한 발표
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- 원본 : <http://git.springsource.org/s2gx-2010/concurrent-programming-distributed-applications/trees/master/concurrency>
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- package : s2gx
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- [Think in java 4th Edition](http://www.yes24.com/24/Goods/263372)
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- 원본 <http://www.mindviewinc.com/TIJ4/CodeDownload.php>
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- 나머지는 직접 작성한 예제
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## 장별 예제 정리 링크
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### 3. java.lang.Thread 바로 알기
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- 쓰지 말아야할 것: Thread.stop
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- [PrimeGenerator.java](src/main/java/net/jcip/examples/PrimeGenerator.java) : 협력적으로 Thread를 멈추는 방식
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- 잘 알고 쓸 것 : Thread.interrupt
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- [SelfInterruption.java](src/main/java/jpz/puzzle84/SelfInterruption.java) : Thread.interrupted()의 혼란성을 보여줌
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- [BrokenPrimeProducer.java](src/main/java/net/jcip/examples/BrokenPrimeProducer.java) : BlockingQueue가 blocking되어 있으면 중지되지 않는 쓰레드
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- [PrimeProducer.java](src/main/java/net/jcip/examples/PrimeProducer.java) : interrupt로 중지할 수 있는 쓰레드
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### 4. 동기화와 가시성
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- Sychronized
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- [NonreentrantDeadlock.java](src/main/java/net/jcip/examples/NonreentrantDeadlock.java) : synchronized 키워드에 의한 lock은 재진입가능하다는 것을 보여줌
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- [SyncDemo.java](src/main/java/study/javacon/SyncDemo.java) : synchronized로 선언된 Block이 동시에 실행되지 못함을 보여줌.
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- [PingPong.java](src/main/java/jpz/puzzle76/PingPong.java) : static method의 syncronized 키워드의 동작방식을 보여줌.
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- 가시성 확보
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- [StopThread.java(Broken)](src/main/java/ej2/item66/broken/StopThread.java) : static 변수이지만 가시성 확보가 안 되어서 한 스레드에서 write한 값이 다른 thread에서 안 보이는 현상을 보여줌.
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- [StopThread.java(Fix1)](src/main/java/ej2/item66/fix1/StopThread.java) : 가시성 문제를 synchronized 메소드를 이용해서 동기화 시켜서 해결
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- [StopThread.java(Fix2)](src/main/java/ej2/item66/fix2/StopThread.java) : 가시성 문제를 volatile 키워드를 이용해서 해결
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- [Worker.java](src/main/java/jpz/puzzle77/Worker.java) : 가시성 확보, 동기화를 모두 했음에도 Thread.join이 호출되면 예상치 못한 동작이 발생함을 보여줌
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### 5. Java concurrent API
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- Executors
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- [TimingThreadPool.java](src/main/java/net/jcip/examples/TimingThreadPool.java) : ThreadPoolExecutor를 확장해서 시간측정 로깅 기능을 추가한 예제
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- Callable
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- [Preloader.java](src/main/java/net/jcip/examples/Preloader.java) : Callable, FutureTask , Thread 생성, Future.get의 사용예.
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- java.util.concurrent.locks패키지
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- [ReadWriterMap.java](src/main/java/net/jcip/examples/ReadWriterMap.java) : ReadWriteLock을 활용해서 Map을 동기화한 사례
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- CountDownLatch
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- [TestHarness.java](src/main/java/net/jcip/examples/TestHarness.java) : CountDownLatch를 이용해서 여러 쓰레드로 작업을 실행하고, 최종 종료시간을 구함
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- [ConcurrentTimer.java](src/main/java/ej2/item69/ConcurrentTimer.java) : TestHarness와 유사한 역할이나 스레드 생성 후에 실행되는 구간을 측정하기 위해 단계를 하나 더 두었음.
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- Semaphore
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- [BoundedHashSet.java](src/main/java/net/jcip/examples/BoundedHashSet.java) : counting semaphore를 활용해 제한된 크기의 Set을 구현함.
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- 다양한 동기화 방식
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- [CounterDemo.java](src/main/java/s2gx/counter/CounterDemo.java) : Counter의 동작을 확인하는 클래스
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- [LockingCounter.java](src/main/java/s2gx/counter/LockingCounter.java) : WriteLock을 이용한 Counter
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- [SynchronizedCounter.java](src/main/java/s2gx/counter/SynchronizedCounter.java) : synchronized 키워드를 이용한 클래스
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- [AtomicCounter.java](src/main/java/s2gx/counter/AtomicCounter.java) : AtomicInteger를 이용한 클래스
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### 6. Thread 안전 클래스
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- Iterator
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- [IteratorAccessor.java](src/main/java/study/javacon/IteratorAccessor.java) : java.util.ConcurrentModificationException를 드러내주는 예제
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- [HiddenIterator.java](src/main/java/net/jcip/examples/HiddenIterator.java) : Iterator를 명시적으로 호출하지 않았는데도 문제가 되는 경우
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- [HiddenIteratorAccessor.java](src/main/java/net/jcip/examples/HiddenIteratorAccessor.java) : HiddenIterator의 에러를 드러내주는 클래스
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- BlockingQueue
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- [PlainProsumer.java](src/main/java/study/javacon/queue/PlainProsumer.java) : wait, notify를 이용한 큐
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- [BlockingProsumer.java](src/main/java/study/javacon/queue/BlockingProsumer.java) : BlockingQueue를 이용
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- Atomic class
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- [SimulatedCAS.java](src/main/java/net/jcip/examples/SimulatedCAS.java) : CAS 동작의 로직을 보여줌.
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- [CasCounter.java](src/main/java/net/jcip/examples/CasCounter.java) : CAS 로직을 이용한 Counter
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- 설계 원칙
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- StackDemo.java : 쓰레드에 한정되어야할 객체를 콜스택 안에서 local변수로 생성하여 메소드 파라미터로 넘김.
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- ThreadLocalDemo.java : ThreadLocal을 이용.
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### 7. Documentation
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- JCIP annotation
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- [Memo.java](src/main/java/study/javacon/findbugs/Memo.java) : @Immutable로 선언했을 때 Findbugs를 경고를 보여줌
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- [LoginInfo.java](src/main/java/study/javacon/findbugs/LoginInfo.java) : Thread-safe하지 않은 클래스
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- [UserService.java](src/main/java/study/javacon/findbugs/UserService.java) : Thread-safe하지 않은 클래스를 멤버변수로 사용하는 코드
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### 8. 성능
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- 락좁히기
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- [AttributeStore.java](src/main/java/net/jcip/examples/AttributeStore.java) : 메소드 단위로 넓게 synchronized 구간을 선엄함.
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- [BetterAttriebuteStore.java](src/main/java/net/jcip/examples/BetterAttributeStore.java) : AttributeStore.java에서 꼭 필요한 부분만 synchronized 구간을 잡음
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- 락분할
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- [ServerStatusBeforeSplit.java](src/main/java/net/jcip/examples/ServerStatusBeforeSplit.java) : 메소드 단위로 넓게 synchronized 구간을 선엄함.
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- [ServerStatusAfterSplit.java](src/main/java/net/jcip/examples/ServerStatusAfterSplit.java) : 메소드별로 필요한 객체에만 synchronized를 걸어서 Lock을 분할.
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- 락스트라이핑
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- [StripedMap.java](src/main/java/net/jcip/examples/StripedMap.java) : 락 스트라이핑을 적용한 Map
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- [DefectedStripedMap.java](src/main/java/study/javacon/DefectedStripedMap.java) : StripedMap에서 Hash방식을 바꿈
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- [DefectedStripedMapTest.java](src/main/java/study/javacon/DefectedStripedMapTest.java) : DefectedStripedMap의 오류를 드러내는 테스트
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- 바쁜 대기 없애기
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- [SlowCountDownLatch.java](src/main/java/ej2/item72/SlowCountDownLatch.java) : CountDownLatch를 무식하게 구현.
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- [BaseBoundBuffer.java](src/main/java/net/jcip/examples/BaseBoundedBuffer.java) : 크기가 한정된 Buffer의 기본 구현.
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- [GrumpyBoundBuffer.java](src/main/java/net/jcip/examples/GrumpyBoundBuffer.java) : 바쁜 대기
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- [SleepyBoundBuffer.java](src/main/java/net/jcip/examples/SleepyBoundBuffer.java) : Sleep을 이용해서 바쁜 대기를 약간 없앰
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- [BoundedBuffer.java](src/main/java/net/jcip/examples/BoundedBuffer.java) : wait, notify를 이용
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- [ConditionBoundBuffer.java](src/main/java/net/jcip/examples/ConditionBoundBuffer.java) : Lock클래스를 이용
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- 늦은 초기화
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- [Initialization.java](src/main/java/ej2/item71/Initialization.java) : lazy initialization의 여러 방식을 보여줌
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- [MySystem.java(Single)](src/main/java/jdm/appendixa/single/MySystem.java) : 초기화 메서드 전체에 동기화가 걸림.
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- [MySystem.java(Double Checked)](src/main/java/jdm/appendixa/doublechecked/MySystem.java) : doublechecked lock을 적용
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- [MySystem.java(Holder)](src/main/java/jdm/appendixa/holder/MySystem.java) : Holder패턴을 적용할려는 예정으로 있는 클래스
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- [ColorPoint.java](src/main/java/jpz/puzzle51/ColorPoint.java) : final필드에 값이 할당되기 전에도 읽는 것이 가능하고, 늦은 초기화가 필요한 경우를 보여줌.

‎pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>net.benelog</groupId>
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<artifactId>java-concurrency</artifactId>
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<name>java-concurrency</name>
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<packaging>jar</packaging>
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<version>1.0.0-BUILD-SNAPSHOT</version>
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<properties>
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<java-version>1.6</java-version>
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<org.slf4j-version>1.5.10</org.slf4j-version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>javax.servlet</groupId>
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<artifactId>javax.servlet-api</artifactId>
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<version>3.0.1</version>
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<scope>provided</scope>
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</dependency>
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<dependency>
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<groupId>net.jcip</groupId>
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<artifactId>jcip-annotations</artifactId>
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<version>1.0</version>
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</dependency>
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<!-- Test -->
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.8.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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<build>
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<finalName>${artifactId}</finalName>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>${java-version}</source>
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<target>${java-version}</target>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-dependency-plugin</artifactId>
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<executions>
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<execution>
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<id>install</id>
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<phase>install</phase>
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<goals>
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<goal>sources</goal>
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</goals>
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</execution>
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</executions>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<configuration>
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<junitArtifactName>junit:junit</junitArtifactName>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</project>

‎src/main/java/ej2/item66/broken/StopThread.java

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/*
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* @(#)StopThread.java $version 2011. 11. 16.
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*
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* Copyright 2007 NHN Corp. All rights Reserved.
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* NHN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*/
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package ej2.item66.broken;
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import java.util.concurrent.TimeUnit;
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/**
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* @author benelog
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*/
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public class StopThread {
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private static Boolean stopRequested = Boolean.FALSE;
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public static void main(String[] args)
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throws InterruptedException {
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Thread backgroundThread = new Thread(new Runnable() {
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public void run() {
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int i = 0;
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while (stopRequested.equals(Boolean.FALSE))
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i++;
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}
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});
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backgroundThread.start();
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TimeUnit.SECONDS.sleep(1);
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stopRequested = Boolean.TRUE;
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}
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}

‎src/main/java/ej2/item66/fix1/StopThread.java

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package ej2.item66.fix1;
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// Properly synchronized cooperative thread termination - Page 261
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import java.util.concurrent.*;
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public class StopThread {
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private static boolean stopRequested;
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private static synchronized void requestStop() {
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stopRequested = true;
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}
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private static synchronized boolean stopRequested() {
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return stopRequested;
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}
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public static void main(String[] args)
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throws InterruptedException {
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Thread backgroundThread = new Thread(new Runnable() {
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public void run() {
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int i = 0;
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while (!stopRequested())
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i++;
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}
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});
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backgroundThread.start();
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TimeUnit.SECONDS.sleep(1);
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requestStop();
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}
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}

‎src/main/java/ej2/item66/fix2/StopThread.java

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package ej2.item66.fix2;
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// Cooperative thread termination with a volatile field
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import java.util.concurrent.*;
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public class StopThread {
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private static volatile boolean stopRequested;
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public static void main(String[] args)
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throws InterruptedException {
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Thread backgroundThread = new Thread(new Runnable() {
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public void run() {
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int i = 0;
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while (!stopRequested)
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i++;
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}
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});
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backgroundThread.start();
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TimeUnit.SECONDS.sleep(1);
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stopRequested = true;
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}
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}

‎src/main/java/ej2/item69/ConcurrentTimer.java

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package ej2.item69;
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import java.util.concurrent.*;
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public class ConcurrentTimer {
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private ConcurrentTimer() { } // Noninstantiable
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public static long time(Executor executor, int concurrency,
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final Runnable action) throws InterruptedException {
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final CountDownLatch ready = new CountDownLatch(concurrency);
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final CountDownLatch start = new CountDownLatch(1);
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final CountDownLatch done = new CountDownLatch(concurrency);
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for (int i = 0; i < concurrency; i++) {
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executor.execute(new Runnable() {
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public void run() {
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ready.countDown(); // Tell timer we're ready
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try {
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start.await(); // Wait till peers are ready
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action.run();
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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} finally {
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done.countDown(); // Tell timer we're done
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}
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}
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});
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}
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ready.await(); // Wait for all workers to be ready
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long startNanos = System.nanoTime();
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start.countDown(); // And they're off!
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done.await(); // Wait for all workers to finish
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return System.nanoTime() - startNanos;
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}
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}

‎src/main/java/ej2/item71/Initialization.java

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package ej2.item71;
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// Initialization styles - Pages 282-284
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public class Initialization {
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// Normal initialization of an instance field - Page 282
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private final FieldType field1 = computeFieldValue();
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// Lazy initialization of instance field - synchronized accessor - Page 282
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private FieldType field2;
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synchronized FieldType getField2() {
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if (field2 == null)
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field2 = computeFieldValue();
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return field2;
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}
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// Lazy initialization holder class idiom for static fields - Page 283
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private static class FieldHolder {
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static final FieldType field = computeFieldValue();
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}
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static FieldType getField3() { return FieldHolder.field; }
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// Double-check idiom for lazy initialization of instance fields - Page 283
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private volatile FieldType field4;
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FieldType getField4() {
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FieldType result = field4;
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if (result == null) { // First check (no locking)
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synchronized(this) {
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result = field4;
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if (result == null) // Second check (with locking)
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field4 = result = computeFieldValue();
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}
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}
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return result;
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}
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// Single-check idiom - can cause repeated initialization! - Page 284
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private volatile FieldType field5;
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private FieldType getField5() {
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FieldType result = field5;
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if (result == null)
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field5 = result = computeFieldValue();
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return result;
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}
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private static FieldType computeFieldValue() {
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return new FieldType();
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}
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}
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class FieldType { }

‎src/main/java/ej2/item72/SlowCountDownLatch.java

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package ej2.item72;
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// Awful CountDownLatch implementation - busy-waits incessantly!
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public class SlowCountDownLatch {
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private int count;
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public SlowCountDownLatch(int count) {
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if (count < 0)
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throw new IllegalArgumentException(count + " < 0");
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this.count = count;
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}
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public void await() {
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while (true) {
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synchronized(this) {
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if (count == 0) return;
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}
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}
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}
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public synchronized void countDown() {
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if (count != 0)
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count--;
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}
23+
}

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