627 lines
19 KiB
Java
627 lines
19 KiB
Java
/*
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* Copyright (C) 2008 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.primitives;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkElementIndex;
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import static com.google.common.base.Preconditions.checkNotNull;
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import static com.google.common.base.Preconditions.checkPositionIndexes;
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import static java.lang.Float.NEGATIVE_INFINITY;
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import static java.lang.Float.POSITIVE_INFINITY;
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import java.io.Serializable;
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import java.util.AbstractList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.List;
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import java.util.RandomAccess;
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import javax.annotation.Nullable;
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import com.google.common.annotations.Beta;
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import com.google.common.annotations.GwtCompatible;
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import com.google.common.annotations.GwtIncompatible;
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import com.google.common.base.Converter;
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/**
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* Static utility methods pertaining to {@code float} primitives, that are not
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* already found in either {@link Float} or {@link Arrays}.
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*
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* <p>
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* See the Guava User Guide article on
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* <a href= "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
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* primitive utilities</a>.
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*
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* @author Kevin Bourrillion
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* @since 1.0
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*/
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@GwtCompatible(emulated = true)
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public final class Floats {
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private Floats() {
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}
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/**
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* The number of bytes required to represent a primitive {@code float} value.
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*
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* @since 10.0
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*/
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public static final int BYTES = Float.SIZE / Byte.SIZE;
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/**
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* Returns a hash code for {@code value}; equal to the result of invoking
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* {@code ((Float) value).hashCode()}.
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*
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* @param value a primitive {@code float} value
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* @return a hash code for the value
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*/
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public static int hashCode(float value) {
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// TODO(kevinb): is there a better way, that's still gwt-safe?
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return ((Float) value).hashCode();
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}
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/**
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* Compares the two specified {@code float} values using
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* {@link Float#compare(float, float)}. You may prefer to invoke that method
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* directly; this method exists only for consistency with the other utilities in
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* this package.
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*
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* <p>
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* <b>Note:</b> this method simply delegates to the JDK method
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* {@link Float#compare}. It is provided for consistency with the other
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* primitive types, whose compare methods were not added to the JDK until JDK 7.
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*
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* @param a the first {@code float} to compare
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* @param b the second {@code float} to compare
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* @return the result of invoking {@link Float#compare(float, float)}
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*/
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public static int compare(float a, float b) {
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return Float.compare(a, b);
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}
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/**
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* Returns {@code true} if {@code value} represents a real number. This is
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* equivalent to, but not necessarily implemented as,
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* {@code !(Float.isInfinite(value) || Float.isNaN(value))}.
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*
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* @since 10.0
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*/
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public static boolean isFinite(float value) {
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return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
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}
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/**
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* Returns {@code true} if {@code target} is present as an element anywhere in
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* {@code array}. Note that this always returns {@code false} when {@code
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* target} is {@code NaN}.
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*
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* @param array an array of {@code float} values, possibly empty
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* @param target a primitive {@code float} value
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* @return {@code true} if {@code array[i] == target} for some value of {@code
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* i}
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*/
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public static boolean contains(float[] array, float target) {
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for (float value : array) {
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if (value == target) {
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return true;
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}
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}
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return false;
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}
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/**
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* Returns the index of the first appearance of the value {@code target} in
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* {@code array}. Note that this always returns {@code -1} when {@code target}
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* is {@code NaN}.
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*
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* @param array an array of {@code float} values, possibly empty
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* @param target a primitive {@code float} value
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* @return the least index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int indexOf(float[] array, float target) {
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return indexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int indexOf(float[] array, float target, int start, int end) {
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for (int i = start; i < end; i++) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the start position of the first occurrence of the specified {@code
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* target} within {@code array}, or {@code -1} if there is no such occurrence.
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*
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* <p>
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* More formally, returns the lowest index {@code i} such that {@code
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* java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
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* the same elements as {@code target}.
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*
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* <p>
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* Note that this always returns {@code -1} when {@code target} contains
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* {@code NaN}.
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*
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* @param array the array to search for the sequence {@code target}
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* @param target the array to search for as a sub-sequence of {@code array}
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*/
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public static int indexOf(float[] array, float[] target) {
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checkNotNull(array, "array");
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checkNotNull(target, "target");
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if (target.length == 0) {
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return 0;
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}
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outer: for (int i = 0; i < array.length - target.length + 1; i++) {
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for (int j = 0; j < target.length; j++) {
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if (array[i + j] != target[j]) {
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continue outer;
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}
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}
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return i;
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}
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return -1;
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}
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/**
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* Returns the index of the last appearance of the value {@code target} in
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* {@code array}. Note that this always returns {@code -1} when {@code target}
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* is {@code NaN}.
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*
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* @param array an array of {@code float} values, possibly empty
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* @param target a primitive {@code float} value
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* @return the greatest index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int lastIndexOf(float[] array, float target) {
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return lastIndexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int lastIndexOf(float[] array, float target, int start, int end) {
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for (int i = end - 1; i >= start; i--) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the least value present in {@code array}, using the same rules of
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* comparison as {@link Math#min(float, float)}.
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*
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* @param array a <i>nonempty</i> array of {@code float} values
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* @return the value present in {@code array} that is less than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static float min(float... array) {
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checkArgument(array.length > 0);
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float min = array[0];
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for (int i = 1; i < array.length; i++) {
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min = Math.min(min, array[i]);
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}
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return min;
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}
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/**
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* Returns the greatest value present in {@code array}, using the same rules of
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* comparison as {@link Math#min(float, float)}.
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*
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* @param array a <i>nonempty</i> array of {@code float} values
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* @return the value present in {@code array} that is greater than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static float max(float... array) {
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checkArgument(array.length > 0);
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float max = array[0];
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for (int i = 1; i < array.length; i++) {
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max = Math.max(max, array[i]);
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}
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return max;
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}
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/**
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* Returns the values from each provided array combined into a single array. For
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* example, {@code concat(new float[] {a, b}, new float[] {}, new float[] {c}}
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* returns the array {@code {a, b, c}}.
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*
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* @param arrays zero or more {@code float} arrays
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* @return a single array containing all the values from the source arrays, in
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* order
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*/
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public static float[] concat(float[]... arrays) {
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int length = 0;
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for (float[] array : arrays) {
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length += array.length;
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}
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float[] result = new float[length];
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int pos = 0;
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for (float[] array : arrays) {
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System.arraycopy(array, 0, result, pos, array.length);
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pos += array.length;
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}
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return result;
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}
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private static final class FloatConverter extends Converter<String, Float> implements Serializable {
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static final FloatConverter INSTANCE = new FloatConverter();
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@Override
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protected Float doForward(String value) {
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return Float.valueOf(value);
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}
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@Override
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protected String doBackward(Float value) {
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return value.toString();
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}
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@Override
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public String toString() {
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return "Floats.stringConverter()";
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}
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private Object readResolve() {
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return INSTANCE;
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}
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private static final long serialVersionUID = 1;
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}
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/**
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* Returns a serializable converter object that converts between strings and
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* floats using {@link Float#valueOf} and {@link Float#toString()}.
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*
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* @since 16.0
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*/
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@Beta
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public static Converter<String, Float> stringConverter() {
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return FloatConverter.INSTANCE;
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}
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/**
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* Returns an array containing the same values as {@code array}, but guaranteed
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* to be of a specified minimum length. If {@code array} already has a length of
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* at least {@code minLength}, it is returned directly. Otherwise, a new array
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* of size {@code minLength + padding} is returned, containing the values of
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* {@code array}, and zeroes in the remaining places.
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*
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* @param array the source array
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* @param minLength the minimum length the returned array must guarantee
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* @param padding an extra amount to "grow" the array by if growth is
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* necessary
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* @throws IllegalArgumentException if {@code minLength} or {@code padding} is
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* negative
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* @return an array containing the values of {@code array}, with guaranteed
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* minimum length {@code minLength}
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*/
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public static float[] ensureCapacity(float[] array, int minLength, int padding) {
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checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
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checkArgument(padding >= 0, "Invalid padding: %s", padding);
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return (array.length < minLength) ? copyOf(array, minLength + padding) : array;
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}
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// Arrays.copyOf() requires Java 6
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private static float[] copyOf(float[] original, int length) {
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float[] copy = new float[length];
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System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
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return copy;
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}
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/**
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* Returns a string containing the supplied {@code float} values, converted to
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* strings as specified by {@link Float#toString(float)}, and separated by
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* {@code separator}. For example, {@code join("-", 1.0f, 2.0f, 3.0f)} returns
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* the string {@code "1.0-2.0-3.0"}.
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*
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* <p>
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* Note that {@link Float#toString(float)} formats {@code float} differently in
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* GWT. In the previous example, it returns the string {@code
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* "1-2-3"}.
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*
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* @param separator the text that should appear between consecutive values in
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* the resulting string (but not at the start or end)
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* @param array an array of {@code float} values, possibly empty
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*/
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public static String join(String separator, float... array) {
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checkNotNull(separator);
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if (array.length == 0) {
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return "";
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}
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// For pre-sizing a builder, just get the right order of magnitude
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StringBuilder builder = new StringBuilder(array.length * 12);
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builder.append(array[0]);
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for (int i = 1; i < array.length; i++) {
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builder.append(separator).append(array[i]);
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}
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return builder.toString();
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}
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/**
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* Returns a comparator that compares two {@code float} arrays
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* lexicographically. That is, it compares, using
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* {@link #compare(float, float)}), the first pair of values that follow any
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* common prefix, or when one array is a prefix of the other, treats the shorter
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* array as the lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f]
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* < [2.0f]}.
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*
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* <p>
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* The returned comparator is inconsistent with {@link Object#equals(Object)}
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* (since arrays support only identity equality), but it is consistent with
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* {@link Arrays#equals(float[], float[])}.
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*
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* @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
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* Lexicographical order article at Wikipedia</a>
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* @since 2.0
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*/
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public static Comparator<float[]> lexicographicalComparator() {
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return LexicographicalComparator.INSTANCE;
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}
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private enum LexicographicalComparator implements Comparator<float[]> {
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INSTANCE;
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@Override
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public int compare(float[] left, float[] right) {
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int minLength = Math.min(left.length, right.length);
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for (int i = 0; i < minLength; i++) {
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int result = Floats.compare(left[i], right[i]);
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if (result != 0) {
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return result;
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}
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}
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return left.length - right.length;
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}
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}
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/**
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* Returns an array containing each value of {@code collection}, converted to a
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* {@code float} value in the manner of {@link Number#floatValue}.
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*
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* <p>
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* Elements are copied from the argument collection as if by {@code
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* collection.toArray()}. Calling this method is as thread-safe as calling that
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* method.
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*
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* @param collection a collection of {@code Number} instances
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* @return an array containing the same values as {@code collection}, in the
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* same order, converted to primitives
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* @throws NullPointerException if {@code collection} or any of its elements is
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* null
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* @since 1.0 (parameter was {@code Collection<Float>} before 12.0)
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*/
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public static float[] toArray(Collection<? extends Number> collection) {
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if (collection instanceof FloatArrayAsList) {
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return ((FloatArrayAsList) collection).toFloatArray();
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}
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Object[] boxedArray = collection.toArray();
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int len = boxedArray.length;
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float[] array = new float[len];
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for (int i = 0; i < len; i++) {
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// checkNotNull for GWT (do not optimize)
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array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue();
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}
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return array;
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}
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/**
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* Returns a fixed-size list backed by the specified array, similar to
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* {@link Arrays#asList(Object[])}. The list supports
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* {@link List#set(int, Object)}, but any attempt to set a value to {@code null}
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* will result in a {@link NullPointerException}.
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*
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* <p>
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* The returned list maintains the values, but not the identities, of
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* {@code Float} objects written to or read from it. For example, whether
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* {@code list.get(0) == list.get(0)} is true for the returned list is
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* unspecified.
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*
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* <p>
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* The returned list may have unexpected behavior if it contains {@code
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* NaN}, or if {@code NaN} is used as a parameter to any of its methods.
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*
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* @param backingArray the array to back the list
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* @return a list view of the array
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*/
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public static List<Float> asList(float... backingArray) {
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if (backingArray.length == 0) {
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return Collections.emptyList();
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}
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return new FloatArrayAsList(backingArray);
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}
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@GwtCompatible
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private static class FloatArrayAsList extends AbstractList<Float> implements RandomAccess, Serializable {
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final float[] array;
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final int start;
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final int end;
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FloatArrayAsList(float[] array) {
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this(array, 0, array.length);
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}
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FloatArrayAsList(float[] array, int start, int end) {
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this.array = array;
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this.start = start;
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this.end = end;
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}
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@Override
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public int size() {
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return end - start;
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}
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@Override
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public boolean isEmpty() {
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return false;
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}
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@Override
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public Float get(int index) {
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checkElementIndex(index, size());
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return array[start + index];
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}
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@Override
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public boolean contains(Object target) {
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// Overridden to prevent a ton of boxing
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return (target instanceof Float) && Floats.indexOf(array, (Float) target, start, end) != -1;
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}
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@Override
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public int indexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Float) {
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int i = Floats.indexOf(array, (Float) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public int lastIndexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Float) {
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int i = Floats.lastIndexOf(array, (Float) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public Float set(int index, Float element) {
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checkElementIndex(index, size());
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float oldValue = array[start + index];
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// checkNotNull for GWT (do not optimize)
|
|
array[start + index] = checkNotNull(element);
|
|
return oldValue;
|
|
}
|
|
|
|
@Override
|
|
public List<Float> subList(int fromIndex, int toIndex) {
|
|
int size = size();
|
|
checkPositionIndexes(fromIndex, toIndex, size);
|
|
if (fromIndex == toIndex) {
|
|
return Collections.emptyList();
|
|
}
|
|
return new FloatArrayAsList(array, start + fromIndex, start + toIndex);
|
|
}
|
|
|
|
@Override
|
|
public boolean equals(Object object) {
|
|
if (object == this) {
|
|
return true;
|
|
}
|
|
if (object instanceof FloatArrayAsList) {
|
|
FloatArrayAsList that = (FloatArrayAsList) 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 + Floats.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();
|
|
}
|
|
|
|
float[] toFloatArray() {
|
|
// Arrays.copyOfRange() is not available under GWT
|
|
int size = size();
|
|
float[] result = new float[size];
|
|
System.arraycopy(array, start, result, 0, size);
|
|
return result;
|
|
}
|
|
|
|
private static final long serialVersionUID = 0;
|
|
}
|
|
|
|
/**
|
|
* Parses the specified string as a single-precision floating point value. The
|
|
* ASCII character {@code '-'} (<code>'\u002D'</code>) is recognized as the
|
|
* minus sign.
|
|
*
|
|
* <p>
|
|
* Unlike {@link Float#parseFloat(String)}, this method returns {@code null}
|
|
* instead of throwing an exception if parsing fails. Valid inputs are exactly
|
|
* those accepted by {@link Float#valueOf(String)}, except that leading and
|
|
* trailing whitespace is not permitted.
|
|
*
|
|
* <p>
|
|
* This implementation is likely to be faster than {@code
|
|
* Float.parseFloat} if many failures are expected.
|
|
*
|
|
* @param string the string representation of a {@code float} 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 float} value
|
|
* @since 14.0
|
|
*/
|
|
@GwtIncompatible("regular expressions")
|
|
@Nullable
|
|
@Beta
|
|
public static Float tryParse(String string) {
|
|
if (Doubles.FLOATING_POINT_PATTERN.matcher(string).matches()) {
|
|
// TODO(user): could be potentially optimized, but only with
|
|
// extensive testing
|
|
try {
|
|
return Float.parseFloat(string);
|
|
} catch (NumberFormatException e) {
|
|
// Float.parseFloat has changed specs several times, so fall through
|
|
// gracefully
|
|
}
|
|
}
|
|
return null;
|
|
}
|
|
}
|