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/*
* 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 com.google.common.annotations.GwtCompatible;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
/**
* Static utility methods pertaining to {@code boolean} primitives, that are not
* already found in either {@link Boolean} or {@link Arrays}.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible
public final class Booleans {
private Booleans() {}
/**
* Returns a hash code for {@code value}; equal to the result of invoking
* {@code ((Boolean) value).hashCode()}.
*
* @param value a primitive {@code boolean} value
* @return a hash code for the value
*/
public static int hashCode(boolean value) {
return value ? 1231 : 1237;
}
/**
* Compares the two specified {@code boolean} values in the standard way
* ({@code false} is considered less than {@code true}). The sign of the
* value returned is the same as that of {@code ((Boolean) a).compareTo(b)}.
*
* @param a the first {@code boolean} to compare
* @param b the second {@code boolean} to compare
* @return a positive number if only {@code a} is {@code true}, a negative
* number if only {@code b} is true, or zero if {@code a == b}
*/
public static int compare(boolean a, boolean b) {
return (a == b) ? 0 : (a ? 1 : -1);
}
/**
* Returns {@code true} if {@code target} is present as an element anywhere in
* {@code array}.
*
* Note: consider representing the array as a {@link
* BitSet} instead, replacing {@code Booleans.contains(array, true)}
* with {@code !bitSet.isEmpty()} and {@code Booleans.contains(array, false)}
* with {@code bitSet.nextClearBit(0) == sizeOfBitSet}.
*
* @param array an array of {@code boolean} values, possibly empty
* @param target a primitive {@code boolean} value
* @return {@code true} if {@code array[i] == target} for some value of {@code
* i}
*/
public static boolean contains(boolean[] array, boolean target) {
for (boolean 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: consider representing the array as a {@link BitSet}
* instead, and using {@link BitSet#nextSetBit(int)} or {@link
* BitSet#nextClearBit(int)}.
*
* @param array an array of {@code boolean} values, possibly empty
* @param target a primitive {@code boolean} 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(boolean[] array, boolean target) {
return indexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int indexOf(
boolean[] array, boolean 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.
*
*
More formally, returns the lowest index {@code i} such that {@code
* java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
* the same elements as {@code target}.
*
* @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(boolean[] array, boolean[] 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}.
*
* @param array an array of {@code boolean} values, possibly empty
* @param target a primitive {@code boolean} 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(boolean[] array, boolean target) {
return lastIndexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int lastIndexOf(
boolean[] array, boolean target, int start, int end) {
for (int i = end - 1; i >= start; i--) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the values from each provided array combined into a single array.
* For example, {@code concat(new boolean[] {a, b}, new boolean[] {}, new
* boolean[] {c}} returns the array {@code {a, b, c}}.
*
* @param arrays zero or more {@code boolean} arrays
* @return a single array containing all the values from the source arrays, in
* order
*/
public static boolean[] concat(boolean[]... arrays) {
int length = 0;
for (boolean[] array : arrays) {
length += array.length;
}
boolean[] result = new boolean[length];
int pos = 0;
for (boolean[] array : arrays) {
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
/**
* 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 boolean[] ensureCapacity(
boolean[] array, int minLength, int padding) {
checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
checkArgument(padding >= 0, "Invalid padding: %s", padding);
return (array.length < minLength)
? copyOf(array, minLength + padding)
: array;
}
// Arrays.copyOf() requires Java 6
private static boolean[] copyOf(boolean[] original, int length) {
boolean[] copy = new boolean[length];
System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
return copy;
}
/**
* Returns a string containing the supplied {@code boolean} values separated
* by {@code separator}. For example, {@code join("-", false, true, false)}
* returns the string {@code "false-true-false"}.
*
* @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 boolean} values, possibly empty
*/
public static String join(String separator, boolean... 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 * 7);
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 boolean} arrays
* lexicographically. That is, it compares, using {@link
* #compare(boolean, boolean)}), 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 [] < [false] < [false, true] < [true]}.
*
*
The returned comparator is inconsistent with {@link
* Object#equals(Object)} (since arrays support only identity equality), but
* it is consistent with {@link Arrays#equals(boolean[], boolean[])}.
*
* @see
* Lexicographical order article at Wikipedia
* @since 2.0
*/
public static Comparator lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
private enum LexicographicalComparator implements Comparator {
INSTANCE;
@Override
public int compare(boolean[] left, boolean[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
int result = Booleans.compare(left[i], right[i]);
if (result != 0) {
return result;
}
}
return left.length - right.length;
}
}
/**
* Copies a collection of {@code Boolean} instances into a new array of
* primitive {@code boolean} values.
*
* Elements are copied from the argument collection as if by {@code
* collection.toArray()}. Calling this method is as thread-safe as calling
* that method.
*
*
Note: consider representing the collection as a {@link
* BitSet} instead.
*
* @param collection a collection of {@code Boolean} objects
* @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
*/
public static boolean[] toArray(Collection collection) {
if (collection instanceof BooleanArrayAsList) {
return ((BooleanArrayAsList) collection).toBooleanArray();
}
Object[] boxedArray = collection.toArray();
int len = boxedArray.length;
boolean[] array = new boolean[len];
for (int i = 0; i < len; i++) {
// checkNotNull for GWT (do not optimize)
array[i] = (Boolean) checkNotNull(boxedArray[i]);
}
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}.
*
* The returned list maintains the values, but not the identities, of
* {@code Boolean} 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.
*
* @param backingArray the array to back the list
* @return a list view of the array
*/
public static List asList(boolean... backingArray) {
if (backingArray.length == 0) {
return Collections.emptyList();
}
return new BooleanArrayAsList(backingArray);
}
@GwtCompatible
private static class BooleanArrayAsList extends AbstractList
implements RandomAccess, Serializable {
final boolean[] array;
final int start;
final int end;
BooleanArrayAsList(boolean[] array) {
this(array, 0, array.length);
}
BooleanArrayAsList(boolean[] 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 Boolean get(int index) {
checkElementIndex(index, size());
return array[start + index];
}
@Override public boolean contains(Object target) {
// Overridden to prevent a ton of boxing
return (target instanceof Boolean)
&& Booleans.indexOf(array, (Boolean) target, start, end) != -1;
}
@Override public int indexOf(Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Boolean) {
int i = Booleans.indexOf(array, (Boolean) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override public int lastIndexOf(Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Boolean) {
int i = Booleans.lastIndexOf(array, (Boolean) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override public Boolean set(int index, Boolean element) {
checkElementIndex(index, size());
boolean oldValue = array[start + index];
array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
return oldValue;
}
@Override public List subList(int fromIndex, int toIndex) {
int size = size();
checkPositionIndexes(fromIndex, toIndex, size);
if (fromIndex == toIndex) {
return Collections.emptyList();
}
return new BooleanArrayAsList(array, start + fromIndex, start + toIndex);
}
@Override public boolean equals(Object object) {
if (object == this) {
return true;
}
if (object instanceof BooleanArrayAsList) {
BooleanArrayAsList that = (BooleanArrayAsList) 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 + Booleans.hashCode(array[i]);
}
return result;
}
@Override public String toString() {
StringBuilder builder = new StringBuilder(size() * 7);
builder.append(array[start] ? "[true" : "[false");
for (int i = start + 1; i < end; i++) {
builder.append(array[i] ? ", true" : ", false");
}
return builder.append(']').toString();
}
boolean[] toBooleanArray() {
// Arrays.copyOfRange() requires Java 6
int size = size();
boolean[] result = new boolean[size];
System.arraycopy(array, start, result, 0, size);
return result;
}
private static final long serialVersionUID = 0;
}
}