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	/*
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	* This file is available under and governed by the GNU General Public
	* License version 2 only, as published by the Free Software Foundation.
	* However, the following notice accompanied the original version of this
	* file:
	*
	* Written by Doug Lea with assistance from members of JCP JSR-166
	* Expert Group and released to the public domain, as explained at
	* http://creativecommons.org/publicdomain/zero/1.0/
	*/

	package java.util.concurrent.atomic;
	import java.util.function.LongUnaryOperator;
	import java.util.function.LongBinaryOperator;
	import sun.misc.Unsafe;

	/**
	* A {@code long} value that may be updated atomically. See the
	* {@link java.util.concurrent.atomic} package specification for
	* description of the properties of atomic variables. An
	* {@code AtomicLong} is used in applications such as atomically
	* incremented sequence numbers, and cannot be used as a replacement
	* for a {@link java.lang.Long}. However, this class does extend
	* {@code Number} to allow uniform access by tools and utilities that
	* deal with numerically-based classes.
	*
	* @since 1.5
	* @author Doug Lea
	*/
	public class AtomicLong extends Number implements java.io.Serializable {
	private static final long serialVersionUID = 1927816293512124184L;

	// setup to use Unsafe.compareAndSwapLong for updates
	private static final Unsafe unsafe = Unsafe.getUnsafe();
	private static final long valueOffset;

	/**
	* Records whether the underlying JVM supports lockless
	* compareAndSwap for longs. While the Unsafe.compareAndSwapLong
	* method works in either case, some constructions should be
	* handled at Java level to avoid locking user-visible locks.
	*/
	static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();

	/**
	* Returns whether underlying JVM supports lockless CompareAndSet
	* for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.
	*/
	private static native boolean VMSupportsCS8();

	static {
	try {
	valueOffset = unsafe.objectFieldOffset
	(AtomicLong.class.getDeclaredField("value"));
	} catch (Exception ex) { throw new Error(ex); }
	}

	private volatile long value;

	/**
	* Creates a new AtomicLong with the given initial value.
	*
	* @param initialValue the initial value
	*/
	public AtomicLong(long initialValue) {
	value = initialValue;
	}

	/**
	* Creates a new AtomicLong with initial value {@code 0}.
	*/
	public AtomicLong() {
	}

	/**
	* Gets the current value.
	*
	* @return the current value
	*/
	public final long get() {
	return value;
	}

	/**
	* Sets to the given value.
	*
	* @param newValue the new value
	*/
	public final void set(long newValue) {
	value = newValue;
	}

	/**
	* Eventually sets to the given value.
	*
	* @param newValue the new value
	* @since 1.6
	*/
	public final void lazySet(long newValue) {
	unsafe.putOrderedLong(this, valueOffset, newValue);
	}

	/**
	* Atomically sets to the given value and returns the old value.
	*
	* @param newValue the new value
	* @return the previous value
	*/
	public final long getAndSet(long newValue) {
	return unsafe.getAndSetLong(this, valueOffset, newValue);
	}

	/**
	* Atomically sets the value to the given updated value
	* if the current value {@code ==} the expected value.
	*
	* @param expect the expected value
	* @param update the new value
	* @return {@code true} if successful. False return indicates that
	* the actual value was not equal to the expected value.
	*/
	public final boolean compareAndSet(long expect, long update) {
	return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
	}

	/**
	* Atomically sets the value to the given updated value
	* if the current value {@code ==} the expected value.
	*
	* <p><a href="package-summary.html#weakCompareAndSet">May fail
	* spuriously and does not provide ordering guarantees</a>, so is
	* only rarely an appropriate alternative to {@code compareAndSet}.
	*
	* @param expect the expected value
	* @param update the new value
	* @return {@code true} if successful
	*/
	public final boolean weakCompareAndSet(long expect, long update) {
	return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
	}

	/**
	* Atomically increments by one the current value.
	*
	* @return the previous value
	*/
	public final long getAndIncrement() {
	return unsafe.getAndAddLong(this, valueOffset, 1L);
	}

	/**
	* Atomically decrements by one the current value.
	*
	* @return the previous value
	*/
	public final long getAndDecrement() {
	return unsafe.getAndAddLong(this, valueOffset, -1L);
	}

	/**
	* Atomically adds the given value to the current value.
	*
	* @param delta the value to add
	* @return the previous value
	*/
	public final long getAndAdd(long delta) {
	return unsafe.getAndAddLong(this, valueOffset, delta);
	}

	/**
	* Atomically increments by one the current value.
	*
	* @return the updated value
	*/
	public final long incrementAndGet() {
	return unsafe.getAndAddLong(this, valueOffset, 1L) + 1L;
	}

	/**
	* Atomically decrements by one the current value.
	*
	* @return the updated value
	*/
	public final long decrementAndGet() {
	return unsafe.getAndAddLong(this, valueOffset, -1L) - 1L;
	}

	/**
	* Atomically adds the given value to the current value.
	*
	* @param delta the value to add
	* @return the updated value
	*/
	public final long addAndGet(long delta) {
	return unsafe.getAndAddLong(this, valueOffset, delta) + delta;
	}

	/**
	* Atomically updates the current value with the results of
	* applying the given function, returning the previous value. The
	* function should be side-effect-free, since it may be re-applied
	* when attempted updates fail due to contention among threads.
	*
	* @param updateFunction a side-effect-free function
	* @return the previous value
	* @since 1.8
	*/
	public final long getAndUpdate(LongUnaryOperator updateFunction) {
	long prev, next;
	do {
	prev = get();
	next = updateFunction.applyAsLong(prev);
	} while (!compareAndSet(prev, next));
	return prev;
	}

	/**
	* Atomically updates the current value with the results of
	* applying the given function, returning the updated value. The
	* function should be side-effect-free, since it may be re-applied
	* when attempted updates fail due to contention among threads.
	*
	* @param updateFunction a side-effect-free function
	* @return the updated value
	* @since 1.8
	*/
	public final long updateAndGet(LongUnaryOperator updateFunction) {
	long prev, next;
	do {
	prev = get();
	next = updateFunction.applyAsLong(prev);
	} while (!compareAndSet(prev, next));
	return next;
	}

	/**
	* Atomically updates the current value with the results of
	* applying the given function to the current and given values,
	* returning the previous value. The function should be
	* side-effect-free, since it may be re-applied when attempted
	* updates fail due to contention among threads. The function
	* is applied with the current value as its first argument,
	* and the given update as the second argument.
	*
	* @param x the update value
	* @param accumulatorFunction a side-effect-free function of two arguments
	* @return the previous value
	* @since 1.8
	*/
	public final long getAndAccumulate(long x,
	LongBinaryOperator accumulatorFunction) {
	long prev, next;
	do {
	prev = get();
	next = accumulatorFunction.applyAsLong(prev, x);
	} while (!compareAndSet(prev, next));
	return prev;
	}

	/**
	* Atomically updates the current value with the results of
	* applying the given function to the current and given values,
	* returning the updated value. The function should be
	* side-effect-free, since it may be re-applied when attempted
	* updates fail due to contention among threads. The function
	* is applied with the current value as its first argument,
	* and the given update as the second argument.
	*
	* @param x the update value
	* @param accumulatorFunction a side-effect-free function of two arguments
	* @return the updated value
	* @since 1.8
	*/
	public final long accumulateAndGet(long x,
	LongBinaryOperator accumulatorFunction) {
	long prev, next;
	do {
	prev = get();
	next = accumulatorFunction.applyAsLong(prev, x);
	} while (!compareAndSet(prev, next));
	return next;
	}

	/**
	* Returns the String representation of the current value.
	* @return the String representation of the current value
	*/
	public String toString() {
	return Long.toString(get());
	}

	/**
	* Returns the value of this {@code AtomicLong} as an {@code int}
	* after a narrowing primitive conversion.
	* @jls 5.1.3 Narrowing Primitive Conversions
	*/
	public int intValue() {
	return (int)get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code long}.
	*/
	public long longValue() {
	return get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code float}
	* after a widening primitive conversion.
	* @jls 5.1.2 Widening Primitive Conversions
	*/
	public float floatValue() {
	return (float)get();
	}

	/**
	* Returns the value of this {@code AtomicLong} as a {@code double}
	* after a widening primitive conversion.
	* @jls 5.1.2 Widening Primitive Conversions
	*/
	public double doubleValue() {
	return (double)get();
	}

	}

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