feat(jdk8): move files to new folder to avoid resources compiled.

jdkSrc/jdk8/java/util/concurrent/atomic/DoubleAccumulator.java

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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.io.Serializable;
+import java.util.function.DoubleBinaryOperator;
+
+/**
+ * One or more variables that together maintain a running {@code double}
+ * value updated using a supplied function.  When updates (method
+ * {@link #accumulate}) are contended across threads, the set of variables
+ * may grow dynamically to reduce contention.  Method {@link #get}
+ * (or, equivalently, {@link #doubleValue}) returns the current value
+ * across the variables maintaining updates.
+ *
+ * <p>This class is usually preferable to alternatives when multiple
+ * threads update a common value that is used for purposes such as
+ * summary statistics that are frequently updated but less frequently
+ * read.
+ *
+ * <p>The supplied accumulator 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.  For example, to maintain a running maximum value, you
+ * could supply {@code Double::max} along with {@code
+ * Double.NEGATIVE_INFINITY} as the identity. The order of
+ * accumulation within or across threads is not guaranteed. Thus, this
+ * class may not be applicable if numerical stability is required,
+ * especially when combining values of substantially different orders
+ * of magnitude.
+ *
+ * <p>Class {@link DoubleAdder} provides analogs of the functionality
+ * of this class for the common special case of maintaining sums.  The
+ * call {@code new DoubleAdder()} is equivalent to {@code new
+ * DoubleAccumulator((x, y) -> x + y, 0.0)}.
+ *
+ * <p>This class extends {@link Number}, but does <em>not</em> define
+ * methods such as {@code equals}, {@code hashCode} and {@code
+ * compareTo} because instances are expected to be mutated, and so are
+ * not useful as collection keys.
+ *
+ * @since 1.8
+ * @author Doug Lea
+ */
+public class DoubleAccumulator extends Striped64 implements Serializable {
+    private static final long serialVersionUID = 7249069246863182397L;
+
+    private final DoubleBinaryOperator function;
+    private final long identity; // use long representation
+
+    /**
+     * Creates a new instance using the given accumulator function
+     * and identity element.
+     * @param accumulatorFunction a side-effect-free function of two arguments
+     * @param identity identity (initial value) for the accumulator function
+     */
+    public DoubleAccumulator(DoubleBinaryOperator accumulatorFunction,
+                             double identity) {
+        this.function = accumulatorFunction;
+        base = this.identity = Double.doubleToRawLongBits(identity);
+    }
+
+    /**
+     * Updates with the given value.
+     *
+     * @param x the value
+     */
+    public void accumulate(double x) {
+        Cell[] as; long b, v, r; int m; Cell a;
+        if ((as = cells) != null ||
+            (r = Double.doubleToRawLongBits
+             (function.applyAsDouble
+              (Double.longBitsToDouble(b = base), x))) != b  && !casBase(b, r)) {
+            boolean uncontended = true;
+            if (as == null || (m = as.length - 1) < 0 ||
+                (a = as[getProbe() & m]) == null ||
+                !(uncontended =
+                  (r = Double.doubleToRawLongBits
+                   (function.applyAsDouble
+                    (Double.longBitsToDouble(v = a.value), x))) == v ||
+                  a.cas(v, r)))
+                doubleAccumulate(x, function, uncontended);
+        }
+    }
+
+    /**
+     * Returns the current value.  The returned value is <em>NOT</em>
+     * an atomic snapshot; invocation in the absence of concurrent
+     * updates returns an accurate result, but concurrent updates that
+     * occur while the value is being calculated might not be
+     * incorporated.
+     *
+     * @return the current value
+     */
+    public double get() {
+        Cell[] as = cells; Cell a;
+        double result = Double.longBitsToDouble(base);
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null)
+                    result = function.applyAsDouble
+                        (result, Double.longBitsToDouble(a.value));
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Resets variables maintaining updates to the identity value.
+     * This method may be a useful alternative to creating a new
+     * updater, but is only effective if there are no concurrent
+     * updates.  Because this method is intrinsically racy, it should
+     * only be used when it is known that no threads are concurrently
+     * updating.
+     */
+    public void reset() {
+        Cell[] as = cells; Cell a;
+        base = identity;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null)
+                    a.value = identity;
+            }
+        }
+    }
+
+    /**
+     * Equivalent in effect to {@link #get} followed by {@link
+     * #reset}. This method may apply for example during quiescent
+     * points between multithreaded computations.  If there are
+     * updates concurrent with this method, the returned value is
+     * <em>not</em> guaranteed to be the final value occurring before
+     * the reset.
+     *
+     * @return the value before reset
+     */
+    public double getThenReset() {
+        Cell[] as = cells; Cell a;
+        double result = Double.longBitsToDouble(base);
+        base = identity;
+        if (as != null) {
+            for (int i = 0; i < as.length; ++i) {
+                if ((a = as[i]) != null) {
+                    double v = Double.longBitsToDouble(a.value);
+                    a.value = identity;
+                    result = function.applyAsDouble(result, v);
+                }
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Returns the String representation of the current value.
+     * @return the String representation of the current value
+     */
+    public String toString() {
+        return Double.toString(get());
+    }
+
+    /**
+     * Equivalent to {@link #get}.
+     *
+     * @return the current value
+     */
+    public double doubleValue() {
+        return get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code long}
+     * after a narrowing primitive conversion.
+     */
+    public long longValue() {
+        return (long)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as an {@code int}
+     * after a narrowing primitive conversion.
+     */
+    public int intValue() {
+        return (int)get();
+    }
+
+    /**
+     * Returns the {@linkplain #get current value} as a {@code float}
+     * after a narrowing primitive conversion.
+     */
+    public float floatValue() {
+        return (float)get();
+    }
+
+    /**
+     * Serialization proxy, used to avoid reference to the non-public
+     * Striped64 superclass in serialized forms.
+     * @serial include
+     */
+    private static class SerializationProxy implements Serializable {
+        private static final long serialVersionUID = 7249069246863182397L;
+
+        /**
+         * The current value returned by get().
+         * @serial
+         */
+        private final double value;
+        /**
+         * The function used for updates.
+         * @serial
+         */
+        private final DoubleBinaryOperator function;
+        /**
+         * The identity value
+         * @serial
+         */
+        private final long identity;
+
+        SerializationProxy(DoubleAccumulator a) {
+            function = a.function;
+            identity = a.identity;
+            value = a.get();
+        }
+
+        /**
+         * Returns a {@code DoubleAccumulator} object with initial state
+         * held by this proxy.
+         *
+         * @return a {@code DoubleAccumulator} object with initial state
+         * held by this proxy.
+         */
+        private Object readResolve() {
+            double d = Double.longBitsToDouble(identity);
+            DoubleAccumulator a = new DoubleAccumulator(function, d);
+            a.base = Double.doubleToRawLongBits(value);
+            return a;
+        }
+    }
+
+    /**
+     * Returns a
+     * <a href="../../../../serialized-form.html#java.util.concurrent.atomic.DoubleAccumulator.SerializationProxy">
+     * SerializationProxy</a>
+     * representing the state of this instance.
+     *
+     * @return a {@link SerializationProxy}
+     * representing the state of this instance
+     */
+    private Object writeReplace() {
+        return new SerializationProxy(this);
+    }
+
+    /**
+     * @param s the stream
+     * @throws java.io.InvalidObjectException always
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.InvalidObjectException {
+        throw new java.io.InvalidObjectException("Proxy required");
+    }
+
+}