Java example source code file (AtomicDoubleArray.java)

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Java - Java tags/keywords

atomicdoublearray, atomiclongarray, canignorereturnvalue, classnotfoundexception, gwtincompatible, stringbuilder

The AtomicDoubleArray.java Java example source code

/*
 * 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/
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/extra/AtomicDoubleArray.java?revision=1.5
 * (Modified to adapt to guava coding conventions and
 * to use AtomicLongArray instead of sun.misc.Unsafe)
 */

package com.google.common.util.concurrent;

import static java.lang.Double.doubleToRawLongBits;
import static java.lang.Double.longBitsToDouble;

import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.concurrent.atomic.AtomicLongArray;

/**
 * A {@code double} 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.
 *
 * <p>This class compares primitive {@code double}
 * values in methods such as {@link #compareAndSet} by comparing their
 * bitwise representation using {@link Double#doubleToRawLongBits},
 * which differs from both the primitive double {@code ==} operator
 * and from {@link Double#equals}, as if implemented by:
 *  <pre> {@code
 * static boolean bitEquals(double x, double y) {
 *   long xBits = Double.doubleToRawLongBits(x);
 *   long yBits = Double.doubleToRawLongBits(y);
 *   return xBits == yBits;
 * }}</pre>
 *
 * @author Doug Lea
 * @author Martin Buchholz
 * @since 11.0
 */
@GwtIncompatible
public class AtomicDoubleArray implements java.io.Serializable {
  private static final long serialVersionUID = 0L;

  // Making this non-final is the lesser evil according to Effective
  // Java 2nd Edition Item 76: Write readObject methods defensively.
  private transient AtomicLongArray longs;

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

  /**
   * Creates a new {@code AtomicDoubleArray} 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 AtomicDoubleArray(double[] array) {
    final int len = array.length;
    long[] longArray = new long[len];
    for (int i = 0; i < len; i++) {
      longArray[i] = doubleToRawLongBits(array[i]);
    }
    this.longs = new AtomicLongArray(longArray);
  }

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

  /**
   * Gets the current value at position {@code i}.
   *
   * @param i the index
   * @return the current value
   */
  public final double get(int i) {
    return longBitsToDouble(longs.get(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, double newValue) {
    long next = doubleToRawLongBits(newValue);
    longs.set(i, next);
  }

  /**
   * Eventually sets the element at position {@code i} to the given value.
   *
   * @param i the index
   * @param newValue the new value
   */
  public final void lazySet(int i, double newValue) {
    set(i, newValue);
    // TODO(user): replace with code below when jdk5 support is dropped.
    // long next = doubleToRawLongBits(newValue);
    // longs.lazySet(i, next);
  }

  /**
   * 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 double getAndSet(int i, double newValue) {
    long next = doubleToRawLongBits(newValue);
    return longBitsToDouble(longs.getAndSet(i, next));
  }

  /**
   * Atomically sets the element at position {@code i} to the given
   * updated value
   * if the current value is <a href="#bitEquals">bitwise equal
   * to 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, double expect, double update) {
    return longs.compareAndSet(i,
                               doubleToRawLongBits(expect),
                               doubleToRawLongBits(update));
  }

  /**
   * Atomically sets the element at position {@code i} to the given
   * updated value
   * if the current value is <a href="#bitEquals">bitwise equal
   * to the expected value.
   *
   * <p>May 

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