com.google.common.primitives.Booleans Maven / Gradle / Ivy
/*
* 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.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.CheckForNull;
/**
* Static utility methods pertaining to {@code boolean} primitives, that are not already found in
* either {@link Boolean} or {@link Arrays}.
*
* See the Guava User Guide article on primitive utilities.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Booleans {
private Booleans() {}
/** Comparators for {@code Boolean} values. */
private enum BooleanComparator implements Comparator {
TRUE_FIRST(1, "Booleans.trueFirst()"),
FALSE_FIRST(-1, "Booleans.falseFirst()");
private final int trueValue;
private final String toString;
BooleanComparator(int trueValue, String toString) {
this.trueValue = trueValue;
this.toString = toString;
}
@Override
public int compare(Boolean a, Boolean b) {
int aVal = a ? trueValue : 0;
int bVal = b ? trueValue : 0;
return bVal - aVal;
}
@Override
public String toString() {
return toString;
}
}
/**
* Returns a {@code Comparator} that sorts {@code true} before {@code false}.
*
* This is particularly useful in Java 8+ in combination with {@code Comparators.comparing},
* e.g. {@code Comparators.comparing(Foo::hasBar, trueFirst())}.
*
* @since 21.0
*/
public static Comparator trueFirst() {
return BooleanComparator.TRUE_FIRST;
}
/**
* Returns a {@code Comparator} that sorts {@code false} before {@code true}.
*
* This is particularly useful in Java 8+ in combination with {@code Comparators.comparing},
* e.g. {@code Comparators.comparing(Foo::hasBar, falseFirst())}.
*
* @since 21.0
*/
public static Comparator falseFirst() {
return BooleanComparator.FALSE_FIRST;
}
/**
* Returns a hash code for {@code value}; equal to the result of invoking {@code ((Boolean)
* value).hashCode()}.
*
* Java 8 users: use {@link Boolean#hashCode(boolean)} instead.
*
* @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)}.
*
*
Note for Java 7 and later: this method should be treated as deprecated; use the
* equivalent {@link Boolean#compare} method instead.
*
* @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 java.util.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 java.util.BitSet} instead, and
* using {@link java.util.BitSet#nextSetBit(int)} or {@link java.util.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 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) ? Arrays.copyOf(array, minLength + padding) : array;
}
/**
* 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[])}.
*
* @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;
}
@Override
public String toString() {
return "Booleans.lexicographicalComparator()";
}
}
/**
* 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 java.util.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}.
*
* There are at most two distinct objects in this list, {@code (Boolean) true} and {@code
* (Boolean) false}. Java guarantees that those are always represented by the same objects.
*
*
The returned list is serializable.
*
* @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(@CheckForNull 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(@CheckForNull 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(@CheckForNull 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];
// checkNotNull for GWT (do not optimize)
array[start + index] = checkNotNull(element);
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(@CheckForNull 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() {
return Arrays.copyOfRange(array, start, end);
}
private static final long serialVersionUID = 0;
}
/**
* Returns the number of {@code values} that are {@code true}.
*
* @since 16.0
*/
public static int countTrue(boolean... values) {
int count = 0;
for (boolean value : values) {
if (value) {
count++;
}
}
return count;
}
/**
* Reverses the elements of {@code array}. This is equivalent to {@code
* Collections.reverse(Booleans.asList(array))}, but is likely to be more efficient.
*
* @since 23.1
*/
public static void reverse(boolean[] 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(Booleans.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(boolean[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
boolean tmp = array[i];
array[i] = array[j];
array[j] = tmp;
}
}
/**
* Performs a right rotation of {@code array} of "distance" places, so that the first element is
* moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
* + i) mod array.length}. This is equivalent to {@code Collections.rotate(Booleans.asList(array),
* distance)}, but is somewhat faster.
*
* The provided "distance" may be negative, which will rotate left.
*
* @since 32.0.0
*/
public static void rotate(boolean[] array, int distance) {
rotate(array, distance, 0, array.length);
}
/**
* Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code
* toIndex} exclusive. This is equivalent to {@code
* Collections.rotate(Booleans.asList(array).subList(fromIndex, toIndex), distance)}, but is
* somewhat faster.
*
*
The provided "distance" may be negative, which will rotate left.
*
* @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
* {@code toIndex > fromIndex}
* @since 32.0.0
*/
public static void rotate(boolean[] array, int distance, int fromIndex, int toIndex) {
// See Ints.rotate for more details about possible algorithms here.
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
if (array.length <= 1) {
return;
}
int length = toIndex - fromIndex;
// Obtain m = (-distance mod length), a non-negative value less than "length". This is how many
// places left to rotate.
int m = -distance % length;
m = (m < 0) ? m + length : m;
// The current index of what will become the first element of the rotated section.
int newFirstIndex = m + fromIndex;
if (newFirstIndex == fromIndex) {
return;
}
reverse(array, fromIndex, newFirstIndex);
reverse(array, newFirstIndex, toIndex);
reverse(array, fromIndex, toIndex);
}
}