public static void main(String[] args) throws InterruptedException {
    LongAccumulator accumulator = new LongAccumulator(Long::max, Long.MIN_VALUE);
    Thread[] ts = new Thread[1000];

    for(int i=0;i<1000;i++){
        ts[i] = new Thread(()->{
            Random random = new Random();
            long value = random.nextLong();
            accumulator.accumulate(value);
        });
        ts[i].start();
    }
    for(int i=0;i<1000;i++){
        ts[i].join();
    }
    System.out.println(accumulator.longValue());
}
 

public static void main(String[] args) throws Exception{
    LongAccumulator accumulator=new LongAccumulator(Long::max,Long.MIN_VALUE);
    Thread[] ts=new Thread[100];

    for(int i=0;i<100;i++){
        ts[i]=new Thread(()->{
            Random random=new Random();
            long value=random.nextLong();
            accumulator.accumulate(value);
        });
        ts[i].start();
    }

    for(int i=0;i<100;i++){
        ts[i].join();
    }
    System.out.println(accumulator.longValue());
}
 

/**
 * accumulates by multiple threads produce correct result
 */
public void testAccumulateAndGetMT() {
    final int incs = 1000000;
    final int nthreads = 4;
    final ExecutorService pool = Executors.newCachedThreadPool();
    LongAccumulator a = new LongAccumulator(Long::max, 0L);
    Phaser phaser = new Phaser(nthreads + 1);
    for (int i = 0; i < nthreads; ++i)
        pool.execute(new AccTask(a, phaser, incs));
    phaser.arriveAndAwaitAdvance();
    phaser.arriveAndAwaitAdvance();
    long expected = incs - 1;
    long result = a.get();
    assertEquals(expected, result);
    pool.shutdown();
}
 

public static void main(String[] args) throws Exception{
    LongAccumulator accumulator=new LongAccumulator(Long::max,Long.MIN_VALUE);
    Thread[] ts=new Thread[100];

    for(int i=0;i<100;i++){
        ts[i]=new Thread(()->{
            Random random=new Random();
            long value=random.nextLong();
            accumulator.accumulate(value);
        });
        ts[i].start();
    }

    for(int i=0;i<100;i++){
        ts[i].join();
    }
    System.out.println(accumulator.longValue());
}
 

/**
 * accumulates by multiple threads produce correct result
 */
public void testAccumulateAndGetMT() {
    final int incs = 1000000;
    final int nthreads = 4;
    final ExecutorService pool = Executors.newCachedThreadPool();
    LongAccumulator a = new LongAccumulator(Long::max, 0L);
    Phaser phaser = new Phaser(nthreads + 1);
    for (int i = 0; i < nthreads; ++i)
        pool.execute(new AccTask(a, phaser, incs));
    phaser.arriveAndAwaitAdvance();
    phaser.arriveAndAwaitAdvance();
    long expected = incs - 1;
    long result = a.get();
    assertEquals(expected, result);
    pool.shutdown();
}
 

/**
 * Constructor to initialize QueryScheduler
 * @param queryExecutor QueryExecutor engine to use
 * @param resourceManager for managing server thread resources
 * @param serverMetrics server metrics collector
 */
public QueryScheduler(@Nonnull Configuration config, @Nonnull QueryExecutor queryExecutor,
    @Nonnull ResourceManager resourceManager, @Nonnull ServerMetrics serverMetrics,
    @Nonnull LongAccumulator latestQueryTime) {
  Preconditions.checkNotNull(config);
  Preconditions.checkNotNull(queryExecutor);
  Preconditions.checkNotNull(resourceManager);
  Preconditions.checkNotNull(serverMetrics);

  this.serverMetrics = serverMetrics;
  this.resourceManager = resourceManager;
  this.queryExecutor = queryExecutor;
  this.latestQueryTime = latestQueryTime;
  this.queryLogRateLimiter = RateLimiter.create(config.getDouble(QUERY_LOG_MAX_RATE_KEY, DEFAULT_QUERY_LOG_MAX_RATE));
  this.numDroppedLogRateLimiter = RateLimiter.create(1.0d);
  this.numDroppedLogCounter = new AtomicInteger(0);

  LOGGER.info("Query log max rate: {}", queryLogRateLimiter.getRate());
}
 

@Test
public void givenLongAccumulator_whenApplyActionOnItFromMultipleThrads_thenShouldProduceProperResult() throws InterruptedException {
    // given
    ExecutorService executorService = Executors.newFixedThreadPool(8);
    LongBinaryOperator sum = Long::sum;
    LongAccumulator accumulator = new LongAccumulator(sum, 0L);
    int numberOfThreads = 4;
    int numberOfIncrements = 100;

    // when
    Runnable accumulateAction = () -> IntStream.rangeClosed(0, numberOfIncrements).forEach(accumulator::accumulate);

    for (int i = 0; i < numberOfThreads; i++) {
        executorService.execute(accumulateAction);
    }

    // then
    executorService.awaitTermination(500, TimeUnit.MILLISECONDS);
    executorService.shutdown();
    assertEquals(accumulator.get(), 20200);

}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

/**
 * Copy the mappings stored in a {@link LocatableResolver} to the specified replica.
 *
 * @param replica The {@link LocatableResolver} to copy to.
 * @return A future that will complete when the copy is finished.
 */
public CompletableFuture<Void> copyToAsync(@Nonnull final LocatableResolver replica) {
    if (!replica.getDatabase().equals(runner.getDatabase())) {
        throw new IllegalArgumentException("copy must be within same database");
    }

    final LongAccumulator maxAccumulator = new LongAccumulator(Long::max, 0L);
    final AtomicInteger counter = new AtomicInteger();
    return copyInternal(replica, maxAccumulator, counter)
            .thenCompose(ignore -> replica.setWindow(maxAccumulator.get()));
}
 

/**
 * LongAccumulator以类型为LongBinaryOperatorlambda表达式构建
 * 而不是仅仅执行加法操作
 */
public void longAccumulatorDemo() {
    ExecutorService executor = Executors.newFixedThreadPool(2);

    LongBinaryOperator op = (x, y) -> 2 * x + y;
    LongAccumulator accumulator = new LongAccumulator(op, 1L);
    IntStream.range(0, 10).forEach(i -> executor.submit(() -> accumulator.accumulate(i)));

    SynchronizationLocks.stopExecutor(executor);
    // => 2539
    System.out.println(accumulator.getThenReset());
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

/**
 * accumulate accumulates given value to current, and get returns current value
 */
public void testAccumulateAndGet() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    ai.accumulate(2);
    assertEquals(2, ai.get());
    ai.accumulate(-4);
    assertEquals(2, ai.get());
    ai.accumulate(4);
    assertEquals(4, ai.get());
}
 

/**
 * reset() causes subsequent get() to return zero
 */
public void testReset() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    ai.accumulate(2);
    assertEquals(2, ai.get());
    ai.reset();
    assertEquals(0, ai.get());
}
 

/**
 * getThenReset() returns current value; subsequent get() returns zero
 */
public void testGetThenReset() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    ai.accumulate(2);
    assertEquals(2, ai.get());
    assertEquals(2, ai.getThenReset());
    assertEquals(0, ai.get());
}
 

/**
 * toString returns current value.
 */
public void testToString() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    assertEquals("0", ai.toString());
    ai.accumulate(1);
    assertEquals(Long.toString(1), ai.toString());
}
 

/**
 * intValue returns current value.
 */
public void testIntValue() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    assertEquals(0, ai.intValue());
    ai.accumulate(1);
    assertEquals(1, ai.intValue());
}
 

/**
 * longValue returns current value.
 */
public void testLongValue() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    assertEquals(0, ai.longValue());
    ai.accumulate(1);
    assertEquals(1, ai.longValue());
}
 

/**
 * floatValue returns current value.
 */
public void testFloatValue() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    assertEquals(0.0f, ai.floatValue());
    ai.accumulate(1);
    assertEquals(1.0f, ai.floatValue());
}
 

/**
 * doubleValue returns current value.
 */
public void testDoubleValue() {
    LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    assertEquals(0.0, ai.doubleValue());
    ai.accumulate(1);
    assertEquals(1.0, ai.doubleValue());
}
 

public void run() {
    phaser.arriveAndAwaitAdvance();
    LongAccumulator a = acc;
    for (int i = 0; i < incs; ++i)
        a.accumulate(i);
    result = a.get();
    phaser.arrive();
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}
 

static void testLongAccumulator() {
    LongBinaryOperator plus = (LongBinaryOperator & Serializable) (x, y) -> x + y;
    LongAccumulator a = new LongAccumulator(plus, -2);
    a.accumulate(34);
    LongAccumulator result = echo(a);
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value");
    a.reset();
    result.reset();
    if (result.get() != a.get())
        throw new RuntimeException("Unexpected value after reset");

    checkSerialClassName(a, "java.util.concurrent.atomic.LongAccumulator$SerializationProxy");
}