com.google.common.primitives.Ints Maven / Gradle / Ivy
Show all versions of guava Show documentation
/*
* 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.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 javax.annotation.CheckForNull;
/**
* Static utility methods pertaining to {@code int} primitives, that are not
* already found in either {@link Integer} or {@link Arrays}.
*
* See the Guava User Guide article on
* primitive utilities.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible(emulated = true)
public final class Ints {
private Ints() {}
/**
* The number of bytes required to represent a primitive {@code int}
* value.
*/
public static final int BYTES = Integer.SIZE / Byte.SIZE;
/**
* The largest power of two that can be represented as an {@code int}.
*
* @since 10.0
*/
public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
/**
* Returns a hash code for {@code value}; equal to the result of invoking
* {@code ((Integer) value).hashCode()}.
*
* @param value a primitive {@code int} value
* @return a hash code for the value
*/
public static int hashCode(int value) {
return value;
}
/**
* Returns the {@code int} value that is equal to {@code value}, if possible.
*
* @param value any value in the range of the {@code int} type
* @return the {@code int} value that equals {@code value}
* @throws IllegalArgumentException if {@code value} is greater than {@link
* Integer#MAX_VALUE} or less than {@link Integer#MIN_VALUE}
*/
public static int checkedCast(long value) {
int result = (int) value;
if (result != value) {
// don't use checkArgument here, to avoid boxing
throw new IllegalArgumentException("Out of range: " + value);
}
return result;
}
/**
* Returns the {@code int} nearest in value to {@code value}.
*
* @param value any {@code long} value
* @return the same value cast to {@code int} if it is in the range of the
* {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
* or {@link Integer#MIN_VALUE} if it is too small
*/
public static int saturatedCast(long value) {
if (value > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
}
if (value < Integer.MIN_VALUE) {
return Integer.MIN_VALUE;
}
return (int) value;
}
/**
* Compares the two specified {@code int} values. The sign of the value
* returned is the same as that of {@code ((Integer) a).compareTo(b)}.
*
*
Note for Java 7 and later: this method should be treated as
* deprecated; use the equivalent {@link Integer#compare} method instead.
*
* @param a the first {@code int} to compare
* @param b the second {@code int} 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(int a, int b) {
return (a < b) ? -1 : ((a > b) ? 1 : 0);
}
/**
* Returns {@code true} if {@code target} is present as an element anywhere in
* {@code array}.
*
* @param array an array of {@code int} values, possibly empty
* @param target a primitive {@code int} value
* @return {@code true} if {@code array[i] == target} for some value of {@code
* i}
*/
public static boolean contains(int[] array, int target) {
for (int value : array) {
if (value == target) {
return true;
}
}
return false;
}
/**
* Returns the index of the first appearance of the value {@code target} in
* {@code array}.
*
* @param array an array of {@code int} values, possibly empty
* @param target a primitive {@code int} 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(int[] array, int target) {
return indexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int indexOf(
int[] array, int 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(int[] array, int[] 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 int} values, possibly empty
* @param target a primitive {@code int} 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(int[] array, int target) {
return lastIndexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int lastIndexOf(
int[] array, int 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}.
*
* @param array a nonempty array of {@code int} 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
*/
public static int min(int... array) {
checkArgument(array.length > 0);
int min = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] < min) {
min = array[i];
}
}
return min;
}
/**
* Returns the greatest value present in {@code array}.
*
* @param array a nonempty array of {@code int} 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
*/
public static int max(int... array) {
checkArgument(array.length > 0);
int max = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] > max) {
max = array[i];
}
}
return max;
}
/**
* Returns the values from each provided array combined into a single array.
* For example, {@code concat(new int[] {a, b}, new int[] {}, new
* int[] {c}} returns the array {@code {a, b, c}}.
*
* @param arrays zero or more {@code int} arrays
* @return a single array containing all the values from the source arrays, in
* order
*/
public static int[] concat(int[]... arrays) {
int length = 0;
for (int[] array : arrays) {
length += array.length;
}
int[] result = new int[length];
int pos = 0;
for (int[] array : arrays) {
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
/**
* Returns a big-endian representation of {@code value} in a 4-element byte
* array; equivalent to {@code ByteBuffer.allocate(4).putInt(value).array()}.
* For example, the input value {@code 0x12131415} would yield the byte array
* {@code {0x12, 0x13, 0x14, 0x15}}.
*
*
If you need to convert and concatenate several values (possibly even of
* different types), use a shared {@link java.nio.ByteBuffer} instance, or use
* {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
* buffer.
*/
@GwtIncompatible("doesn't work")
public static byte[] toByteArray(int value) {
return new byte[] {
(byte) (value >> 24),
(byte) (value >> 16),
(byte) (value >> 8),
(byte) value};
}
/**
* Returns the {@code int} value whose big-endian representation is stored in
* the first 4 bytes of {@code bytes}; equivalent to {@code
* ByteBuffer.wrap(bytes).getInt()}. For example, the input byte array {@code
* {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
* 0x12131415}.
*
*
Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
* library exposes much more flexibility at little cost in readability.
*
* @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
*/
@GwtIncompatible("doesn't work")
public static int fromByteArray(byte[] bytes) {
checkArgument(bytes.length >= BYTES,
"array too small: %s < %s", bytes.length, BYTES);
return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
}
/**
* Returns the {@code int} value whose byte representation is the given 4
* bytes, in big-endian order; equivalent to {@code Ints.fromByteArray(new
* byte[] {b1, b2, b3, b4})}.
*
* @since 7.0
*/
@GwtIncompatible("doesn't work")
public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
}
private static final class IntConverter
extends Converter implements Serializable {
static final IntConverter INSTANCE = new IntConverter();
@Override
protected Integer doForward(String value) {
return Integer.decode(value);
}
@Override
protected String doBackward(Integer value) {
return value.toString();
}
@Override
public String toString() {
return "Ints.stringConverter()";
}
private Object readResolve() {
return INSTANCE;
}
private static final long serialVersionUID = 1;
}
/**
* Returns a serializable converter object that converts between strings and
* integers using {@link Integer#decode} and {@link Integer#toString()}.
*
* @since 16.0
*/
@Beta
public static Converter stringConverter() {
return IntConverter.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 int[] ensureCapacity(
int[] 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 int[] copyOf(int[] original, int length) {
int[] copy = new int[length];
System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
return copy;
}
/**
* Returns a string containing the supplied {@code int} values separated
* by {@code separator}. For example, {@code join("-", 1, 2, 3)} 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 int} values, possibly empty
*/
public static String join(String separator, int... 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 * 5);
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 int} arrays
* lexicographically. That is, it compares, using {@link
* #compare(int, int)}), 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] < [1, 2] < [2]}.
*
* The returned comparator is inconsistent with {@link
* Object#equals(Object)} (since arrays support only identity equality), but
* it is consistent with {@link Arrays#equals(int[], int[])}.
*
* @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(int[] left, int[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
int result = Ints.compare(left[i], right[i]);
if (result != 0) {
return result;
}
}
return left.length - right.length;
}
}
/**
* Returns an array containing each value of {@code collection}, converted to
* a {@code int} value in the manner of {@link Number#intValue}.
*
* 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} before 12.0)
*/
public static int[] toArray(Collection collection) {
if (collection instanceof IntArrayAsList) {
return ((IntArrayAsList) collection).toIntArray();
}
Object[] boxedArray = collection.toArray();
int len = boxedArray.length;
int[] array = new int[len];
for (int i = 0; i < len; i++) {
// checkNotNull for GWT (do not optimize)
array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
}
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 Integer} 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(int... backingArray) {
if (backingArray.length == 0) {
return Collections.emptyList();
}
return new IntArrayAsList(backingArray);
}
@GwtCompatible
private static class IntArrayAsList extends AbstractList
implements RandomAccess, Serializable {
final int[] array;
final int start;
final int end;
IntArrayAsList(int[] array) {
this(array, 0, array.length);
}
IntArrayAsList(int[] 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 Integer 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 Integer)
&& Ints.indexOf(array, (Integer) target, start, end) != -1;
}
@Override public int indexOf(Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Integer) {
int i = Ints.indexOf(array, (Integer) 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 Integer) {
int i = Ints.lastIndexOf(array, (Integer) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override public Integer set(int index, Integer element) {
checkElementIndex(index, size());
int 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 IntArrayAsList(array, start + fromIndex, start + toIndex);
}
@Override public boolean equals(Object object) {
if (object == this) {
return true;
}
if (object instanceof IntArrayAsList) {
IntArrayAsList that = (IntArrayAsList) 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 + Ints.hashCode(array[i]);
}
return result;
}
@Override public String toString() {
StringBuilder builder = new StringBuilder(size() * 5);
builder.append('[').append(array[start]);
for (int i = start + 1; i < end; i++) {
builder.append(", ").append(array[i]);
}
return builder.append(']').toString();
}
int[] toIntArray() {
// Arrays.copyOfRange() is not available under GWT
int size = size();
int[] result = new int[size];
System.arraycopy(array, start, result, 0, size);
return result;
}
private static final long serialVersionUID = 0;
}
private static final byte[] asciiDigits = new byte[128];
static {
Arrays.fill(asciiDigits, (byte) -1);
for (int i = 0; i <= 9; i++) {
asciiDigits['0' + i] = (byte) i;
}
for (int i = 0; i <= 26; i++) {
asciiDigits['A' + i] = (byte) (10 + i);
asciiDigits['a' + i] = (byte) (10 + i);
}
}
private static int digit(char c) {
return (c < 128) ? asciiDigits[c] : -1;
}
/**
* Parses the specified string as a signed decimal integer value. The ASCII
* character {@code '-'} ('\u002D') is recognized as the
* minus sign.
*
* Unlike {@link Integer#parseInt(String)}, this method returns
* {@code null} instead of throwing an exception if parsing fails.
* Additionally, this method only accepts ASCII digits, and returns
* {@code null} if non-ASCII digits are present in the string.
*
*
Note that strings prefixed with ASCII {@code '+'} are rejected, even
* under JDK 7, despite the change to {@link Integer#parseInt(String)} for
* that version.
*
* @param string the string representation of an integer value
* @return the integer value represented by {@code string}, or {@code null} if
* {@code string} has a length of zero or cannot be parsed as an integer
* value
* @since 11.0
*/
@Beta
@CheckForNull
public static Integer tryParse(String string) {
return tryParse(string, 10);
}
/**
* Parses the specified string as a signed integer value using the specified
* radix. The ASCII character {@code '-'} ('\u002D') is
* recognized as the minus sign.
*
*
Unlike {@link Integer#parseInt(String, int)}, this method returns
* {@code null} instead of throwing an exception if parsing fails.
* Additionally, this method only accepts ASCII digits, and returns
* {@code null} if non-ASCII digits are present in the string.
*
*
Note that strings prefixed with ASCII {@code '+'} are rejected, even
* under JDK 7, despite the change to {@link Integer#parseInt(String, int)}
* for that version.
*
* @param string the string representation of an integer value
* @param radix the radix to use when parsing
* @return the integer value represented by {@code string} using
* {@code radix}, or {@code null} if {@code string} has a length of zero
* or cannot be parsed as an integer value
* @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or
* {@code radix > Character.MAX_RADIX}
*/
@CheckForNull static Integer tryParse(
String string, int radix) {
if (checkNotNull(string).isEmpty()) {
return null;
}
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
throw new IllegalArgumentException(
"radix must be between MIN_RADIX and MAX_RADIX but was " + radix);
}
boolean negative = string.charAt(0) == '-';
int index = negative ? 1 : 0;
if (index == string.length()) {
return null;
}
int digit = digit(string.charAt(index++));
if (digit < 0 || digit >= radix) {
return null;
}
int accum = -digit;
int cap = Integer.MIN_VALUE / radix;
while (index < string.length()) {
digit = digit(string.charAt(index++));
if (digit < 0 || digit >= radix || accum < cap) {
return null;
}
accum *= radix;
if (accum < Integer.MIN_VALUE + digit) {
return null;
}
accum -= digit;
}
if (negative) {
return accum;
} else if (accum == Integer.MIN_VALUE) {
return null;
} else {
return -accum;
}
}
}