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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;

/**
 * A {@code long} array in which elements may be updated atomically.
 * See the {@link java.util.concurrent.atomic} package specification
 * for description of the properties of atomic variables.
 * @since 1.5
 * @author Doug Lea
 */
public class AtomicLongArray implements java.io.Serializable {
    private static final long serialVersionUID = -2308431214976778248L;

    private final long[] array;

    /**
     * Creates a new AtomicLongArray of the given length, with all
     * elements initially zero.
     *
     * @param length the length of the array
     */
    public AtomicLongArray(int length) {
        array = new long[length];
    }

    /**
     * Creates a new AtomicLongArray with the same length as, and
     * all elements copied from, the given array.
     *
     * @param array the array to copy elements from
     * @throws NullPointerException if array is null
     */
    public AtomicLongArray(long[] array) {
        // Visibility guaranteed by final field guarantees
        this.array = array.clone();
    }

    /**
     * Returns the length of the array.
     *
     * @return the length of the array
     */
    public final int length() {
        return array.length;
    }

    /**
     * Gets the current value at position {@code i}.
     *
     * @param i the index
     * @return the current value
     */
    public final long get(int i) {
        return array[i];
    }

    /**
     * Sets the element at position {@code i} to the given value.
     *
     * @param i the index
     * @param newValue the new value
     */
    public final void set(int i, long newValue) {
        array[i] = newValue;
    }

    /**
     * Eventually sets the element at position {@code i} to the given value.
     *
     * @param i the index
     * @param newValue the new value
     * @since 1.6
     */
    public final void lazySet(int i, long newValue) {
        array[i] = newValue;
    }


    /**
     * Atomically sets the element at position {@code i} to the given value
     * and returns the old value.
     *
     * @param i the index
     * @param newValue the new value
     * @return the previous value
     */
    public final long getAndSet(int i, long newValue) {
        long v = array[i];
        array[i] = newValue;
        return v;
    }

    /**
     * Atomically sets the element at position {@code i} to the given
     * updated value if the current value {@code ==} the expected value.
     *
     * @param i the index
     * @param expect the expected value
     * @param update the new value
     * @return true if successful. False return indicates that
     * the actual value was not equal to the expected value.
     */
    public final boolean compareAndSet(int i, long expect, long update) {
        if (array[i] == expect) {
            array[i] = update;
            return true;
        } else {
            return false;
        }
    }

    /**
     * Atomically sets the element at position {@code i} to the given
     * updated value if the current value {@code ==} the expected value.
     *
     * 

May fail spuriously * and does not provide ordering guarantees, so is only rarely an * appropriate alternative to {@code compareAndSet}. * * @param i the index * @param expect the expected value * @param update the new value * @return true if successful. */ public final boolean weakCompareAndSet(int i, long expect, long update) { return compareAndSet(i, expect, update); } /** * Atomically increments by one the element at index {@code i}. * * @param i the index * @return the previous value */ public final long getAndIncrement(int i) { return getAndAdd(i, 1); } /** * Atomically decrements by one the element at index {@code i}. * * @param i the index * @return the previous value */ public final long getAndDecrement(int i) { return getAndAdd(i, -1); } /** * Atomically adds the given value to the element at index {@code i}. * * @param i the index * @param delta the value to add * @return the previous value */ public final long getAndAdd(int i, long delta) { long v = array[i]; array[i] += delta; return v; } /** * Atomically increments by one the element at index {@code i}. * * @param i the index * @return the updated value */ public final long incrementAndGet(int i) { return addAndGet(i, 1); } /** * Atomically decrements by one the element at index {@code i}. * * @param i the index * @return the updated value */ public final long decrementAndGet(int i) { return addAndGet(i, -1); } /** * Atomically adds the given value to the element at index {@code i}. * * @param i the index * @param delta the value to add * @return the updated value */ public long addAndGet(int i, long delta) { array[i] += delta; return array[i]; } /** * Returns the String representation of the current values of array. * @return the String representation of the current values of array */ public String toString() { int iMax = array.length - 1; if (iMax == -1) return "[]"; StringBuilder b = new StringBuilder(); b.append('['); for (int i = 0; ; i++) { b.append(get(i)); if (i == iMax) return b.append(']').toString(); b.append(',').append(' '); } } }





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