Doubles.java
/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.primitives;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static com.google.common.base.Strings.lenientFormat;
import static java.lang.Double.NEGATIVE_INFINITY;
import static java.lang.Double.POSITIVE_INFINITY;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Converter;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import java.util.Spliterator;
import java.util.Spliterators;
import javax.annotation.CheckForNull;
/**
* Static utility methods pertaining to {@code double} primitives, that are not already found in
* either {@link Double} or {@link Arrays}.
*
* <p>See the Guava User Guide article on <a
* href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Doubles extends DoublesMethodsForWeb {
private Doubles() {}
/**
* The number of bytes required to represent a primitive {@code double} value.
*
* <p><b>Java 8 users:</b> use {@link Double#BYTES} instead.
*
* @since 10.0
*/
public static final int BYTES = Double.SIZE / Byte.SIZE;
/**
* Returns a hash code for {@code value}; equal to the result of invoking {@code ((Double)
* value).hashCode()}.
*
* <p><b>Java 8 users:</b> use {@link Double#hashCode(double)} instead.
*
* @param value a primitive {@code double} value
* @return a hash code for the value
*/
public static int hashCode(double value) {
return ((Double) value).hashCode();
// TODO(kevinb): do it this way when we can (GWT problem):
// long bits = Double.doubleToLongBits(value);
// return (int) (bits ^ (bits >>> 32));
}
/**
* Compares the two specified {@code double} values. The sign of the value returned is the same as
* that of <code>((Double) a).{@linkplain Double#compareTo compareTo}(b)</code>. As with that
* method, {@code NaN} is treated as greater than all other values, and {@code 0.0 > -0.0}.
*
* <p><b>Note:</b> this method simply delegates to the JDK method {@link Double#compare}. It is
* provided for consistency with the other primitive types, whose compare methods were not added
* to the JDK until JDK 7.
*
* @param a the first {@code double} to compare
* @param b the second {@code double} to compare
* @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
* greater than {@code b}; or zero if they are equal
*/
public static int compare(double a, double b) {
return Double.compare(a, b);
}
/**
* Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not
* necessarily implemented as, {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
*
* <p><b>Java 8 users:</b> use {@link Double#isFinite(double)} instead.
*
* @since 10.0
*/
public static boolean isFinite(double value) {
return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY;
}
/**
* Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note
* that this always returns {@code false} when {@code target} is {@code NaN}.
*
* @param array an array of {@code double} values, possibly empty
* @param target a primitive {@code double} value
* @return {@code true} if {@code array[i] == target} for some value of {@code i}
*/
public static boolean contains(double[] array, double target) {
for (double value : array) {
if (value == target) {
return true;
}
}
return false;
}
/**
* Returns the index of the first appearance of the value {@code target} in {@code array}. Note
* that this always returns {@code -1} when {@code target} is {@code NaN}.
*
* @param array an array of {@code double} values, possibly empty
* @param target a primitive {@code double} value
* @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int indexOf(double[] array, double target) {
return indexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int indexOf(double[] array, double target, int start, int end) {
for (int i = start; i < end; i++) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the start position of the first occurrence of the specified {@code target} within
* {@code array}, or {@code -1} if there is no such occurrence.
*
* <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
* i, i + target.length)} contains exactly the same elements as {@code target}.
*
* <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}.
*
* @param array the array to search for the sequence {@code target}
* @param target the array to search for as a sub-sequence of {@code array}
*/
public static int indexOf(double[] array, double[] target) {
checkNotNull(array, "array");
checkNotNull(target, "target");
if (target.length == 0) {
return 0;
}
outer:
for (int i = 0; i < array.length - target.length + 1; i++) {
for (int j = 0; j < target.length; j++) {
if (array[i + j] != target[j]) {
continue outer;
}
}
return i;
}
return -1;
}
/**
* Returns the index of the last appearance of the value {@code target} in {@code array}. Note
* that this always returns {@code -1} when {@code target} is {@code NaN}.
*
* @param array an array of {@code double} values, possibly empty
* @param target a primitive {@code double} value
* @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int lastIndexOf(double[] array, double target) {
return lastIndexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int lastIndexOf(double[] array, double target, int start, int end) {
for (int i = end - 1; i >= start; i--) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the least value present in {@code array}, using the same rules of comparison as {@link
* Math#min(double, double)}.
*
* @param array a <i>nonempty</i> array of {@code double} values
* @return the value present in {@code array} that is less than or equal to every other value in
* the array
* @throws IllegalArgumentException if {@code array} is empty
*/
@GwtIncompatible(
"Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
public static double min(double... array) {
checkArgument(array.length > 0);
double min = array[0];
for (int i = 1; i < array.length; i++) {
min = Math.min(min, array[i]);
}
return min;
}
/**
* Returns the greatest value present in {@code array}, using the same rules of comparison as
* {@link Math#max(double, double)}.
*
* @param array a <i>nonempty</i> array of {@code double} values
* @return the value present in {@code array} that is greater than or equal to every other value
* in the array
* @throws IllegalArgumentException if {@code array} is empty
*/
@GwtIncompatible(
"Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
public static double max(double... array) {
checkArgument(array.length > 0);
double max = array[0];
for (int i = 1; i < array.length; i++) {
max = Math.max(max, array[i]);
}
return max;
}
/**
* Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
*
* <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
* unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
* value} is greater than {@code max}, {@code max} is returned.
*
* @param value the {@code double} value to constrain
* @param min the lower bound (inclusive) of the range to constrain {@code value} to
* @param max the upper bound (inclusive) of the range to constrain {@code value} to
* @throws IllegalArgumentException if {@code min > max}
* @since 21.0
*/
@Beta
public static double constrainToRange(double value, double min, double max) {
// avoid auto-boxing by not using Preconditions.checkArgument(); see Guava issue 3984
// Reject NaN by testing for the good case (min <= max) instead of the bad (min > max).
if (min <= max) {
return Math.min(Math.max(value, min), max);
}
throw new IllegalArgumentException(
lenientFormat("min (%s) must be less than or equal to max (%s)", min, max));
}
/**
* Returns the values from each provided array combined into a single array. For example, {@code
* concat(new double[] {a, b}, new double[] {}, new double[] {c}} returns the array {@code {a, b,
* c}}.
*
* @param arrays zero or more {@code double} arrays
* @return a single array containing all the values from the source arrays, in order
*/
public static double[] concat(double[]... arrays) {
int length = 0;
for (double[] array : arrays) {
length += array.length;
}
double[] result = new double[length];
int pos = 0;
for (double[] array : arrays) {
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
private static final class DoubleConverter extends Converter<String, Double>
implements Serializable {
static final DoubleConverter INSTANCE = new DoubleConverter();
@Override
protected Double doForward(String value) {
return Double.valueOf(value);
}
@Override
protected String doBackward(Double value) {
return value.toString();
}
@Override
public String toString() {
return "Doubles.stringConverter()";
}
private Object readResolve() {
return INSTANCE;
}
private static final long serialVersionUID = 1;
}
/**
* Returns a serializable converter object that converts between strings and doubles using {@link
* Double#valueOf} and {@link Double#toString()}.
*
* @since 16.0
*/
@Beta
public static Converter<String, Double> stringConverter() {
return DoubleConverter.INSTANCE;
}
/**
* Returns an array containing the same values as {@code array}, but guaranteed to be of a
* specified minimum length. If {@code array} already has a length of at least {@code minLength},
* it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
* returned, containing the values of {@code array}, and zeroes in the remaining places.
*
* @param array the source array
* @param minLength the minimum length the returned array must guarantee
* @param padding an extra amount to "grow" the array by if growth is necessary
* @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
* @return an array containing the values of {@code array}, with guaranteed minimum length {@code
* minLength}
*/
public static double[] ensureCapacity(double[] array, int minLength, int padding) {
checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
checkArgument(padding >= 0, "Invalid padding: %s", padding);
return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
}
/**
* Returns a string containing the supplied {@code double} values, converted to strings as
* specified by {@link Double#toString(double)}, and separated by {@code separator}. For example,
* {@code join("-", 1.0, 2.0, 3.0)} returns the string {@code "1.0-2.0-3.0"}.
*
* <p>Note that {@link Double#toString(double)} formats {@code double} differently in GWT
* sometimes. In the previous example, it returns the string {@code "1-2-3"}.
*
* @param separator the text that should appear between consecutive values in the resulting string
* (but not at the start or end)
* @param array an array of {@code double} values, possibly empty
*/
public static String join(String separator, double... array) {
checkNotNull(separator);
if (array.length == 0) {
return "";
}
// For pre-sizing a builder, just get the right order of magnitude
StringBuilder builder = new StringBuilder(array.length * 12);
builder.append(array[0]);
for (int i = 1; i < array.length; i++) {
builder.append(separator).append(array[i]);
}
return builder.toString();
}
/**
* Returns a comparator that compares two {@code double} arrays <a
* href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
* compares, using {@link #compare(double, double)}), the first pair of values that follow any
* common prefix, or when one array is a prefix of the other, treats the shorter array as the
* lesser. For example, {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
*
* <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
* support only identity equality), but it is consistent with {@link Arrays#equals(double[],
* double[])}.
*
* @since 2.0
*/
public static Comparator<double[]> lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
private enum LexicographicalComparator implements Comparator<double[]> {
INSTANCE;
@Override
public int compare(double[] left, double[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
int result = Double.compare(left[i], right[i]);
if (result != 0) {
return result;
}
}
return left.length - right.length;
}
@Override
public String toString() {
return "Doubles.lexicographicalComparator()";
}
}
/**
* Sorts the elements of {@code array} in descending order.
*
* <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
* all NaN values as equal and 0.0 as greater than -0.0.
*
* @since 23.1
*/
public static void sortDescending(double[] array) {
checkNotNull(array);
sortDescending(array, 0, array.length);
}
/**
* Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
* exclusive in descending order.
*
* <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
* all NaN values as equal and 0.0 as greater than -0.0.
*
* @since 23.1
*/
public static void sortDescending(double[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
Arrays.sort(array, fromIndex, toIndex);
reverse(array, fromIndex, toIndex);
}
/**
* Reverses the elements of {@code array}. This is equivalent to {@code
* Collections.reverse(Doubles.asList(array))}, but is likely to be more efficient.
*
* @since 23.1
*/
public static void reverse(double[] array) {
checkNotNull(array);
reverse(array, 0, array.length);
}
/**
* Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
* exclusive. This is equivalent to {@code
* Collections.reverse(Doubles.asList(array).subList(fromIndex, toIndex))}, but is likely to be
* more efficient.
*
* @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
* {@code toIndex > fromIndex}
* @since 23.1
*/
public static void reverse(double[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
double tmp = array[i];
array[i] = array[j];
array[j] = tmp;
}
}
/**
* Returns an array containing each value of {@code collection}, converted to a {@code double}
* value in the manner of {@link Number#doubleValue}.
*
* <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
* Calling this method is as thread-safe as calling that method.
*
* @param collection a collection of {@code Number} instances
* @return an array containing the same values as {@code collection}, in the same order, converted
* to primitives
* @throws NullPointerException if {@code collection} or any of its elements is null
* @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
*/
public static double[] toArray(Collection<? extends Number> collection) {
if (collection instanceof DoubleArrayAsList) {
return ((DoubleArrayAsList) collection).toDoubleArray();
}
Object[] boxedArray = collection.toArray();
int len = boxedArray.length;
double[] array = new double[len];
for (int i = 0; i < len; i++) {
// checkNotNull for GWT (do not optimize)
array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
}
return array;
}
/**
* Returns a fixed-size list backed by the specified array, similar to {@link
* Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
* set a value to {@code null} will result in a {@link NullPointerException}.
*
* <p>The returned list maintains the values, but not the identities, of {@code Double} objects
* written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
* the returned list is unspecified.
*
* <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN}
* is used as a parameter to any of its methods.
*
* <p><b>Note:</b> when possible, you should represent your data as an {@link
* ImmutableDoubleArray} instead, which has an {@link ImmutableDoubleArray#asList asList} view.
*
* @param backingArray the array to back the list
* @return a list view of the array
*/
public static List<Double> asList(double... backingArray) {
if (backingArray.length == 0) {
return Collections.emptyList();
}
return new DoubleArrayAsList(backingArray);
}
@GwtCompatible
private static class DoubleArrayAsList extends AbstractList<Double>
implements RandomAccess, Serializable {
final double[] array;
final int start;
final int end;
DoubleArrayAsList(double[] array) {
this(array, 0, array.length);
}
DoubleArrayAsList(double[] array, int start, int end) {
this.array = array;
this.start = start;
this.end = end;
}
@Override
public int size() {
return end - start;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public Double get(int index) {
checkElementIndex(index, size());
return array[start + index];
}
@Override
public Spliterator.OfDouble spliterator() {
return Spliterators.spliterator(array, start, end, 0);
}
@Override
public boolean contains(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
return (target instanceof Double)
&& Doubles.indexOf(array, (Double) target, start, end) != -1;
}
@Override
public int indexOf(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Double) {
int i = Doubles.indexOf(array, (Double) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public int lastIndexOf(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Double) {
int i = Doubles.lastIndexOf(array, (Double) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public Double set(int index, Double element) {
checkElementIndex(index, size());
double oldValue = array[start + index];
// checkNotNull for GWT (do not optimize)
array[start + index] = checkNotNull(element);
return oldValue;
}
@Override
public List<Double> subList(int fromIndex, int toIndex) {
int size = size();
checkPositionIndexes(fromIndex, toIndex, size);
if (fromIndex == toIndex) {
return Collections.emptyList();
}
return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
}
@Override
public boolean equals(@CheckForNull Object object) {
if (object == this) {
return true;
}
if (object instanceof DoubleArrayAsList) {
DoubleArrayAsList that = (DoubleArrayAsList) object;
int size = size();
if (that.size() != size) {
return false;
}
for (int i = 0; i < size; i++) {
if (array[start + i] != that.array[that.start + i]) {
return false;
}
}
return true;
}
return super.equals(object);
}
@Override
public int hashCode() {
int result = 1;
for (int i = start; i < end; i++) {
result = 31 * result + Doubles.hashCode(array[i]);
}
return result;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(size() * 12);
builder.append('[').append(array[start]);
for (int i = start + 1; i < end; i++) {
builder.append(", ").append(array[i]);
}
return builder.append(']').toString();
}
double[] toDoubleArray() {
return Arrays.copyOfRange(array, start, end);
}
private static final long serialVersionUID = 0;
}
/**
* This is adapted from the regex suggested by {@link Double#valueOf(String)} for prevalidating
* inputs. All valid inputs must pass this regex, but it's semantically fine if not all inputs
* that pass this regex are valid -- only a performance hit is incurred, not a semantics bug.
*/
@GwtIncompatible // regular expressions
static final
java.util.regex.Pattern
FLOATING_POINT_PATTERN = fpPattern();
@GwtIncompatible // regular expressions
private static
java.util.regex.Pattern
fpPattern() {
/*
* We use # instead of * for possessive quantifiers. This lets us strip them out when building
* the regex for RE2 (which doesn't support them) but leave them in when building it for
* java.util.regex (where we want them in order to avoid catastrophic backtracking).
*/
String decimal = "(?:\\d+#(?:\\.\\d*#)?|\\.\\d+#)";
String completeDec = decimal + "(?:[eE][+-]?\\d+#)?[fFdD]?";
String hex = "(?:[0-9a-fA-F]+#(?:\\.[0-9a-fA-F]*#)?|\\.[0-9a-fA-F]+#)";
String completeHex = "0[xX]" + hex + "[pP][+-]?\\d+#[fFdD]?";
String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
fpPattern =
fpPattern.replace(
"#",
"+"
);
return
java.util.regex.Pattern
.compile(fpPattern);
}
/**
* Parses the specified string as a double-precision floating point value. The ASCII character
* {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign.
*
* <p>Unlike {@link Double#parseDouble(String)}, this method returns {@code null} instead of
* throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link
* Double#valueOf(String)}, except that leading and trailing whitespace is not permitted.
*
* <p>This implementation is likely to be faster than {@code Double.parseDouble} if many failures
* are expected.
*
* @param string the string representation of a {@code double} value
* @return the floating point value represented by {@code string}, or {@code null} if {@code
* string} has a length of zero or cannot be parsed as a {@code double} value
* @throws NullPointerException if {@code string} is {@code null}
* @since 14.0
*/
@Beta
@GwtIncompatible // regular expressions
@CheckForNull
public static Double tryParse(String string) {
if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
// TODO(lowasser): could be potentially optimized, but only with
// extensive testing
try {
return Double.parseDouble(string);
} catch (NumberFormatException e) {
// Double.parseDouble has changed specs several times, so fall through
// gracefully
}
}
return null;
}
}