Java tutorial
/* * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.lang.annotation.Native; import java.lang.invoke.MethodHandles; import java.lang.constant.Constable; import java.lang.constant.ConstantDesc; import java.util.Objects; import java.util.Optional; import jdk.internal.HotSpotIntrinsicCandidate; import jdk.internal.misc.VM; import static java.lang.String.COMPACT_STRINGS; import static java.lang.String.LATIN1; import static java.lang.String.UTF16; /** * The {@code Integer} class wraps a value of the primitive type * {@code int} in an object. An object of type {@code Integer} * contains a single field whose type is {@code int}. * * <p>In addition, this class provides several methods for converting * an {@code int} to a {@code String} and a {@code String} to an * {@code int}, as well as other constants and methods useful when * dealing with an {@code int}. * * <p>Implementation note: The implementations of the "bit twiddling" * methods (such as {@link #highestOneBit(int) highestOneBit} and * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are * based on material from Henry S. Warren, Jr.'s <i>Hacker's * Delight</i>, (Addison Wesley, 2002). * * @author Lee Boynton * @author Arthur van Hoff * @author Josh Bloch * @author Joseph D. Darcy * @since 1.0 */ public final class Integer extends Number implements Comparable<Integer>, Constable, ConstantDesc { /** * A constant holding the minimum value an {@code int} can * have, -2<sup>31</sup>. */ @Native public static final int MIN_VALUE = 0x80000000; /** * A constant holding the maximum value an {@code int} can * have, 2<sup>31</sup>-1. */ @Native public static final int MAX_VALUE = 0x7fffffff; /** * The {@code Class} instance representing the primitive type * {@code int}. * * @since 1.1 */ @SuppressWarnings("unchecked") public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int"); /** * All possible chars for representing a number as a String */ static final char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' }; /** * Returns a string representation of the first argument in the * radix specified by the second argument. * * <p>If the radix is smaller than {@code Character.MIN_RADIX} * or larger than {@code Character.MAX_RADIX}, then the radix * {@code 10} is used instead. * * <p>If the first argument is negative, the first element of the * result is the ASCII minus character {@code '-'} * ({@code '\u005Cu002D'}). If the first argument is not * negative, no sign character appears in the result. * * <p>The remaining characters of the result represent the magnitude * of the first argument. If the magnitude is zero, it is * represented by a single zero character {@code '0'} * ({@code '\u005Cu0030'}); otherwise, the first character of * the representation of the magnitude will not be the zero * character. The following ASCII characters are used as digits: * * <blockquote> * {@code 0123456789abcdefghijklmnopqrstuvwxyz} * </blockquote> * * These are {@code '\u005Cu0030'} through * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through * {@code '\u005Cu007A'}. If {@code radix} is * <var>N</var>, then the first <var>N</var> of these characters * are used as radix-<var>N</var> digits in the order shown. Thus, * the digits for hexadecimal (radix 16) are * {@code 0123456789abcdef}. If uppercase letters are * desired, the {@link java.lang.String#toUpperCase()} method may * be called on the result: * * <blockquote> * {@code Integer.toString(n, 16).toUpperCase()} * </blockquote> * * @param i an integer to be converted to a string. * @param radix the radix to use in the string representation. * @return a string representation of the argument in the specified radix. * @see java.lang.Character#MAX_RADIX * @see java.lang.Character#MIN_RADIX */ public static String toString(int i, int radix) { if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) radix = 10; /* Use the faster version */ if (radix == 10) { return toString(i); } if (COMPACT_STRINGS) { byte[] buf = new byte[33]; boolean negative = (i < 0); int charPos = 32; if (!negative) { i = -i; } while (i <= -radix) { buf[charPos--] = (byte) digits[-(i % radix)]; i = i / radix; } buf[charPos] = (byte) digits[-i]; if (negative) { buf[--charPos] = '-'; } return StringLatin1.newString(buf, charPos, (33 - charPos)); } return toStringUTF16(i, radix); } private static String toStringUTF16(int i, int radix) { byte[] buf = new byte[33 * 2]; boolean negative = (i < 0); int charPos = 32; if (!negative) { i = -i; } while (i <= -radix) { StringUTF16.putChar(buf, charPos--, digits[-(i % radix)]); i = i / radix; } StringUTF16.putChar(buf, charPos, digits[-i]); if (negative) { StringUTF16.putChar(buf, --charPos, '-'); } return StringUTF16.newString(buf, charPos, (33 - charPos)); } /** * Returns a string representation of the first argument as an * unsigned integer value in the radix specified by the second * argument. * * <p>If the radix is smaller than {@code Character.MIN_RADIX} * or larger than {@code Character.MAX_RADIX}, then the radix * {@code 10} is used instead. * * <p>Note that since the first argument is treated as an unsigned * value, no leading sign character is printed. * * <p>If the magnitude is zero, it is represented by a single zero * character {@code '0'} ({@code '\u005Cu0030'}); otherwise, * the first character of the representation of the magnitude will * not be the zero character. * * <p>The behavior of radixes and the characters used as digits * are the same as {@link #toString(int, int) toString}. * * @param i an integer to be converted to an unsigned string. * @param radix the radix to use in the string representation. * @return an unsigned string representation of the argument in the specified radix. * @see #toString(int, int) * @since 1.8 */ public static String toUnsignedString(int i, int radix) { return Long.toUnsignedString(toUnsignedLong(i), radix); } /** * Returns a string representation of the integer argument as an * unsigned integer in base 16. * * <p>The unsigned integer value is the argument plus 2<sup>32</sup> * if the argument is negative; otherwise, it is equal to the * argument. This value is converted to a string of ASCII digits * in hexadecimal (base 16) with no extra leading * {@code 0}s. * * <p>The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Integer#parseUnsignedInt(String, int) * Integer.parseUnsignedInt(s, 16)}. * * <p>If the unsigned magnitude is zero, it is represented by a * single zero character {@code '0'} ({@code '\u005Cu0030'}); * otherwise, the first character of the representation of the * unsigned magnitude will not be the zero character. The * following characters are used as hexadecimal digits: * * <blockquote> * {@code 0123456789abcdef} * </blockquote> * * These are the characters {@code '\u005Cu0030'} through * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through * {@code '\u005Cu0066'}. If uppercase letters are * desired, the {@link java.lang.String#toUpperCase()} method may * be called on the result: * * <blockquote> * {@code Integer.toHexString(n).toUpperCase()} * </blockquote> * * @param i an integer to be converted to a string. * @return the string representation of the unsigned integer value * represented by the argument in hexadecimal (base 16). * @see #parseUnsignedInt(String, int) * @see #toUnsignedString(int, int) * @since 1.0.2 */ public static String toHexString(int i) { return toUnsignedString0(i, 4); } /** * Returns a string representation of the integer argument as an * unsigned integer in base 8. * * <p>The unsigned integer value is the argument plus 2<sup>32</sup> * if the argument is negative; otherwise, it is equal to the * argument. This value is converted to a string of ASCII digits * in octal (base 8) with no extra leading {@code 0}s. * * <p>The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Integer#parseUnsignedInt(String, int) * Integer.parseUnsignedInt(s, 8)}. * * <p>If the unsigned magnitude is zero, it is represented by a * single zero character {@code '0'} ({@code '\u005Cu0030'}); * otherwise, the first character of the representation of the * unsigned magnitude will not be the zero character. The * following characters are used as octal digits: * * <blockquote> * {@code 01234567} * </blockquote> * * These are the characters {@code '\u005Cu0030'} through * {@code '\u005Cu0037'}. * * @param i an integer to be converted to a string. * @return the string representation of the unsigned integer value * represented by the argument in octal (base 8). * @see #parseUnsignedInt(String, int) * @see #toUnsignedString(int, int) * @since 1.0.2 */ public static String toOctalString(int i) { return toUnsignedString0(i, 3); } /** * Returns a string representation of the integer argument as an * unsigned integer in base 2. * * <p>The unsigned integer value is the argument plus 2<sup>32</sup> * if the argument is negative; otherwise it is equal to the * argument. This value is converted to a string of ASCII digits * in binary (base 2) with no extra leading {@code 0}s. * * <p>The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Integer#parseUnsignedInt(String, int) * Integer.parseUnsignedInt(s, 2)}. * * <p>If the unsigned magnitude is zero, it is represented by a * single zero character {@code '0'} ({@code '\u005Cu0030'}); * otherwise, the first character of the representation of the * unsigned magnitude will not be the zero character. The * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code * '1'} ({@code '\u005Cu0031'}) are used as binary digits. * * @param i an integer to be converted to a string. * @return the string representation of the unsigned integer value * represented by the argument in binary (base 2). * @see #parseUnsignedInt(String, int) * @see #toUnsignedString(int, int) * @since 1.0.2 */ public static String toBinaryString(int i) { return toUnsignedString0(i, 1); } /** * Convert the integer to an unsigned number. */ private static String toUnsignedString0(int val, int shift) { // assert shift > 0 && shift <=5 : "Illegal shift value"; int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val); int chars = Math.max(((mag + (shift - 1)) / shift), 1); if (COMPACT_STRINGS) { byte[] buf = new byte[chars]; formatUnsignedInt(val, shift, buf, 0, chars); return new String(buf, LATIN1); } else { byte[] buf = new byte[chars * 2]; formatUnsignedIntUTF16(val, shift, buf, 0, chars); return new String(buf, UTF16); } } /** * Format an {@code int} (treated as unsigned) into a character buffer. If * {@code len} exceeds the formatted ASCII representation of {@code val}, * {@code buf} will be padded with leading zeroes. * * @param val the unsigned int to format * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) * @param buf the character buffer to write to * @param offset the offset in the destination buffer to start at * @param len the number of characters to write */ static void formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) { // assert shift > 0 && shift <=5 : "Illegal shift value"; // assert offset >= 0 && offset < buf.length : "illegal offset"; // assert len > 0 && (offset + len) <= buf.length : "illegal length"; int charPos = offset + len; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = Integer.digits[val & mask]; val >>>= shift; } while (charPos > offset); } /** byte[]/LATIN1 version */ static void formatUnsignedInt(int val, int shift, byte[] buf, int offset, int len) { int charPos = offset + len; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = (byte) Integer.digits[val & mask]; val >>>= shift; } while (charPos > offset); } /** byte[]/UTF16 version */ private static void formatUnsignedIntUTF16(int val, int shift, byte[] buf, int offset, int len) { int charPos = offset + len; int radix = 1 << shift; int mask = radix - 1; do { StringUTF16.putChar(buf, --charPos, Integer.digits[val & mask]); val >>>= shift; } while (charPos > offset); } static final byte[] DigitTens = { '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '1', '1', '1', '1', '1', '1', '1', '1', '1', '1', '2', '2', '2', '2', '2', '2', '2', '2', '2', '2', '3', '3', '3', '3', '3', '3', '3', '3', '3', '3', '4', '4', '4', '4', '4', '4', '4', '4', '4', '4', '5', '5', '5', '5', '5', '5', '5', '5', '5', '5', '6', '6', '6', '6', '6', '6', '6', '6', '6', '6', '7', '7', '7', '7', '7', '7', '7', '7', '7', '7', '8', '8', '8', '8', '8', '8', '8', '8', '8', '8', '9', '9', '9', '9', '9', '9', '9', '9', '9', '9', }; static final byte[] DigitOnes = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', }; /** * Returns a {@code String} object representing the * specified integer. The argument is converted to signed decimal * representation and returned as a string, exactly as if the * argument and radix 10 were given as arguments to the {@link * #toString(int, int)} method. * * @param i an integer to be converted. * @return a string representation of the argument in base 10. */ @HotSpotIntrinsicCandidate public static String toString(int i) { int size = stringSize(i); if (COMPACT_STRINGS) { byte[] buf = new byte[size]; getChars(i, size, buf); return new String(buf, LATIN1); } else { byte[] buf = new byte[size * 2]; StringUTF16.getChars(i, size, buf); return new String(buf, UTF16); } } /** * Returns a string representation of the argument as an unsigned * decimal value. * * The argument is converted to unsigned decimal representation * and returned as a string exactly as if the argument and radix * 10 were given as arguments to the {@link #toUnsignedString(int, * int)} method. * * @param i an integer to be converted to an unsigned string. * @return an unsigned string representation of the argument. * @see #toUnsignedString(int, int) * @since 1.8 */ public static String toUnsignedString(int i) { return Long.toString(toUnsignedLong(i)); } /** * Places characters representing the integer i into the * character array buf. The characters are placed into * the buffer backwards starting with the least significant * digit at the specified index (exclusive), and working * backwards from there. * * @implNote This method converts positive inputs into negative * values, to cover the Integer.MIN_VALUE case. Converting otherwise * (negative to positive) will expose -Integer.MIN_VALUE that overflows * integer. * * @param i value to convert * @param index next index, after the least significant digit * @param buf target buffer, Latin1-encoded * @return index of the most significant digit or minus sign, if present */ static int getChars(int i, int index, byte[] buf) { int q, r; int charPos = index; boolean negative = i < 0; if (!negative) { i = -i; } // Generate two digits per iteration while (i <= -100) { q = i / 100; r = (q * 100) - i; i = q; buf[--charPos] = DigitOnes[r]; buf[--charPos] = DigitTens[r]; } // We know there are at most two digits left at this point. q = i / 10; r = (q * 10) - i; buf[--charPos] = (byte) ('0' + r); // Whatever left is the remaining digit. if (q < 0) { buf[--charPos] = (byte) ('0' - q); } if (negative) { buf[--charPos] = (byte) '-'; } return charPos; } // Left here for compatibility reasons, see JDK-8143900. static final int[] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 99999999, 999999999, Integer.MAX_VALUE }; /** * Returns the string representation size for a given int value. * * @param x int value * @return string size * * @implNote There are other ways to compute this: e.g. binary search, * but values are biased heavily towards zero, and therefore linear search * wins. The iteration results are also routinely inlined in the generated * code after loop unrolling. */ static int stringSize(int x) { int d = 1; if (x >= 0) { d = 0; x = -x; } int p = -10; for (int i = 1; i < 10; i++) { if (x > p) return i + d; p = 10 * p; } return 10 + d; } /** * Parses the string argument as a signed integer in the radix * specified by the second argument. The characters in the string * must all be digits of the specified radix (as determined by * whether {@link java.lang.Character#digit(char, int)} returns a * nonnegative value), except that the first character may be an * ASCII minus sign {@code '-'} ({@code '\u005Cu002D'}) to * indicate a negative value or an ASCII plus sign {@code '+'} * ({@code '\u005Cu002B'}) to indicate a positive value. The * resulting integer value is returned. * * <p>An exception of type {@code NumberFormatException} is * thrown if any of the following situations occurs: * <ul> * <li>The first argument is {@code null} or is a string of * length zero. * * <li>The radix is either smaller than * {@link java.lang.Character#MIN_RADIX} or * larger than {@link java.lang.Character#MAX_RADIX}. * * <li>Any character of the string is not a digit of the specified * radix, except that the first character may be a minus sign * {@code '-'} ({@code '\u005Cu002D'}) or plus sign * {@code '+'} ({@code '\u005Cu002B'}) provided that the * string is longer than length 1. * * <li>The value represented by the string is not a value of type * {@code int}. * </ul> * * <p>Examples: * <blockquote><pre> * parseInt("0", 10) returns 0 * parseInt("473", 10) returns 473 * parseInt("+42", 10) returns 42 * parseInt("-0", 10) returns 0 * parseInt("-FF", 16) returns -255 * parseInt("1100110", 2) returns 102 * parseInt("2147483647", 10) returns 2147483647 * parseInt("-2147483648", 10) returns -2147483648 * parseInt("2147483648", 10) throws a NumberFormatException * parseInt("99", 8) throws a NumberFormatException * parseInt("Kona", 10) throws a NumberFormatException * parseInt("Kona", 27) returns 411787 * </pre></blockquote> * * @param s the {@code String} containing the integer * representation to be parsed * @param radix the radix to be used while parsing {@code s}. * @return the integer represented by the string argument in the * specified radix. * @exception NumberFormatException if the {@code String} * does not contain a parsable {@code int}. */ public static int parseInt(String s, int radix) throws NumberFormatException { /* * WARNING: This method may be invoked early during VM initialization * before IntegerCache is initialized. Care must be taken to not use * the valueOf method. */ if (s == null) { throw new NumberFormatException("null"); } if (radix < Character.MIN_RADIX) { throw new NumberFormatException("radix " + radix + " less than Character.MIN_RADIX"); } if (radix > Character.MAX_RADIX) { throw new NumberFormatException("radix " + radix + " greater than Character.MAX_RADIX"); } boolean negative = false; int i = 0, len = s.length(); int limit = -Integer.MAX_VALUE; if (len > 0) { char firstChar = s.charAt(0); if (firstChar < '0') { // Possible leading "+" or "-" if (firstChar == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (firstChar != '+') { throw NumberFormatException.forInputString(s, radix); } if (len == 1) { // Cannot have lone "+" or "-" throw NumberFormatException.forInputString(s, radix); } i++; } int multmin = limit / radix; int result = 0; while (i < len) { // Accumulating negatively avoids surprises near MAX_VALUE int digit = Character.digit(s.charAt(i++), radix); if (digit < 0 || result < multmin) { throw NumberFormatException.forInputString(s, radix); } result *= radix; if (result < limit + digit) { throw NumberFormatException.forInputString(s, radix); } result -= digit; } return negative ? result : -result; } else { throw NumberFormatException.forInputString(s, radix); } } /** * Parses the {@link CharSequence} argument as a signed {@code int} in the * specified {@code radix}, beginning at the specified {@code beginIndex} * and extending to {@code endIndex - 1}. * * <p>The method does not take steps to guard against the * {@code CharSequence} being mutated while parsing. * * @param s the {@code CharSequence} containing the {@code int} * representation to be parsed * @param beginIndex the beginning index, inclusive. * @param endIndex the ending index, exclusive. * @param radix the radix to be used while parsing {@code s}. * @return the signed {@code int} represented by the subsequence in * the specified radix. * @throws NullPointerException if {@code s} is null. * @throws IndexOutOfBoundsException if {@code beginIndex} is * negative, or if {@code beginIndex} is greater than * {@code endIndex} or if {@code endIndex} is greater than * {@code s.length()}. * @throws NumberFormatException if the {@code CharSequence} does not * contain a parsable {@code int} in the specified * {@code radix}, or if {@code radix} is either smaller than * {@link java.lang.Character#MIN_RADIX} or larger than * {@link java.lang.Character#MAX_RADIX}. * @since 9 */ public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException { s = Objects.requireNonNull(s); if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) { throw new IndexOutOfBoundsException(); } if (radix < Character.MIN_RADIX) { throw new NumberFormatException("radix " + radix + " less than Character.MIN_RADIX"); } if (radix > Character.MAX_RADIX) { throw new NumberFormatException("radix " + radix + " greater than Character.MAX_RADIX"); } boolean negative = false; int i = beginIndex; int limit = -Integer.MAX_VALUE; if (i < endIndex) { char firstChar = s.charAt(i); if (firstChar < '0') { // Possible leading "+" or "-" if (firstChar == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (firstChar != '+') { throw NumberFormatException.forCharSequence(s, beginIndex, endIndex, i); } i++; if (i == endIndex) { // Cannot have lone "+" or "-" throw NumberFormatException.forCharSequence(s, beginIndex, endIndex, i); } } int multmin = limit / radix; int result = 0; while (i < endIndex) { // Accumulating negatively avoids surprises near MAX_VALUE int digit = Character.digit(s.charAt(i), radix); if (digit < 0 || result < multmin) { throw NumberFormatException.forCharSequence(s, beginIndex, endIndex, i); } result *= radix; if (result < limit + digit) { throw NumberFormatException.forCharSequence(s, beginIndex, endIndex, i); } i++; result -= digit; } return negative ? result : -result; } else { throw NumberFormatException.forInputString("", radix); } } /** * Parses the string argument as a signed decimal integer. The * characters in the string must all be decimal digits, except * that the first character may be an ASCII minus sign {@code '-'} * ({@code '\u005Cu002D'}) to indicate a negative value or an * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to * indicate a positive value. The resulting integer value is * returned, exactly as if the argument and the radix 10 were * given as arguments to the {@link #parseInt(java.lang.String, * int)} method. * * @param s a {@code String} containing the {@code int} * representation to be parsed * @return the integer value represented by the argument in decimal. * @exception NumberFormatException if the string does not contain a * parsable integer. */ public static int parseInt(String s) throws NumberFormatException { return parseInt(s, 10); } /** * Parses the string argument as an unsigned integer in the radix * specified by the second argument. An unsigned integer maps the * values usually associated with negative numbers to positive * numbers larger than {@code MAX_VALUE}. * * The characters in the string must all be digits of the * specified radix (as determined by whether {@link * java.lang.Character#digit(char, int)} returns a nonnegative * value), except that the first character may be an ASCII plus * sign {@code '+'} ({@code '\u005Cu002B'}). The resulting * integer value is returned. * * <p>An exception of type {@code NumberFormatException} is * thrown if any of the following situations occurs: * <ul> * <li>The first argument is {@code null} or is a string of * length zero. * * <li>The radix is either smaller than * {@link java.lang.Character#MIN_RADIX} or * larger than {@link java.lang.Character#MAX_RADIX}. * * <li>Any character of the string is not a digit of the specified * radix, except that the first character may be a plus sign * {@code '+'} ({@code '\u005Cu002B'}) provided that the * string is longer than length 1. * * <li>The value represented by the string is larger than the * largest unsigned {@code int}, 2<sup>32</sup>-1. * * </ul> * * * @param s the {@code String} containing the unsigned integer * representation to be parsed * @param radix the radix to be used while parsing {@code s}. * @return the integer represented by the string argument in the * specified radix. * @throws NumberFormatException if the {@code String} * does not contain a parsable {@code int}. * @since 1.8 */ public static int parseUnsignedInt(String s, int radix) throws NumberFormatException { if (s == null) { throw new NumberFormatException("null"); } int len = s.length(); if (len > 0) { char firstChar = s.charAt(0); if (firstChar == '-') { throw new NumberFormatException( String.format("Illegal leading minus sign " + "on unsigned string %s.", s)); } else { if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits return parseInt(s, radix); } else { long ell = Long.parseLong(s, radix); if ((ell & 0xffff_ffff_0000_0000L) == 0) { return (int) ell; } else { throw new NumberFormatException( String.format("String value %s exceeds " + "range of unsigned int.", s)); } } } } else { throw NumberFormatException.forInputString(s, radix); } } /** * Parses the {@link CharSequence} argument as an unsigned {@code int} in * the specified {@code radix}, beginning at the specified * {@code beginIndex} and extending to {@code endIndex - 1}. * * <p>The method does not take steps to guard against the * {@code CharSequence} being mutated while parsing. * * @param s the {@code CharSequence} containing the unsigned * {@code int} representation to be parsed * @param beginIndex the beginning index, inclusive. * @param endIndex the ending index, exclusive. * @param radix the radix to be used while parsing {@code s}. * @return the unsigned {@code int} represented by the subsequence in * the specified radix. * @throws NullPointerException if {@code s} is null. * @throws IndexOutOfBoundsException if {@code beginIndex} is * negative, or if {@code beginIndex} is greater than * {@code endIndex} or if {@code endIndex} is greater than * {@code s.length()}. * @throws NumberFormatException if the {@code CharSequence} does not * contain a parsable unsigned {@code int} in the specified * {@code radix}, or if {@code radix} is either smaller than * {@link java.lang.Character#MIN_RADIX} or larger than * {@link java.lang.Character#MAX_RADIX}. * @since 9 */ public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException { s = Objects.requireNonNull(s); if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) { throw new IndexOutOfBoundsException(); } int start = beginIndex, len = endIndex - beginIndex; if (len > 0) { char firstChar = s.charAt(start); if (firstChar == '-') { throw new NumberFormatException( String.format("Illegal leading minus sign " + "on unsigned string %s.", s)); } else { if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits return parseInt(s, start, start + len, radix); } else { long ell = Long.parseLong(s, start, start + len, radix); if ((ell & 0xffff_ffff_0000_0000L) == 0) { return (int) ell; } else { throw new NumberFormatException( String.format("String value %s exceeds " + "range of unsigned int.", s)); } } } } else { throw new NumberFormatException(""); } } /** * Parses the string argument as an unsigned decimal integer. The * characters in the string must all be decimal digits, except * that the first character may be an ASCII plus sign {@code * '+'} ({@code '\u005Cu002B'}). The resulting integer value * is returned, exactly as if the argument and the radix 10 were * given as arguments to the {@link * #parseUnsignedInt(java.lang.String, int)} method. * * @param s a {@code String} containing the unsigned {@code int} * representation to be parsed * @return the unsigned integer value represented by the argument in decimal. * @throws NumberFormatException if the string does not contain a * parsable unsigned integer. * @since 1.8 */ public static int parseUnsignedInt(String s) throws NumberFormatException { return parseUnsignedInt(s, 10); } /** * Returns an {@code Integer} object holding the value * extracted from the specified {@code String} when parsed * with the radix given by the second argument. The first argument * is interpreted as representing a signed integer in the radix * specified by the second argument, exactly as if the arguments * were given to the {@link #parseInt(java.lang.String, int)} * method. The result is an {@code Integer} object that * represents the integer value specified by the string. * * <p>In other words, this method returns an {@code Integer} * object equal to the value of: * * <blockquote> * {@code new Integer(Integer.parseInt(s, radix))} * </blockquote> * * @param s the string to be parsed. * @param radix the radix to be used in interpreting {@code s} * @return an {@code Integer} object holding the value * represented by the string argument in the specified * radix. * @exception NumberFormatException if the {@code String} * does not contain a parsable {@code int}. */ public static Integer valueOf(String s, int radix) throws NumberFormatException { return Integer.valueOf(parseInt(s, radix)); } /** * Returns an {@code Integer} object holding the * value of the specified {@code String}. The argument is * interpreted as representing a signed decimal integer, exactly * as if the argument were given to the {@link * #parseInt(java.lang.String)} method. The result is an * {@code Integer} object that represents the integer value * specified by the string. * * <p>In other words, this method returns an {@code Integer} * object equal to the value of: * * <blockquote> * {@code new Integer(Integer.parseInt(s))} * </blockquote> * * @param s the string to be parsed. * @return an {@code Integer} object holding the value * represented by the string argument. * @exception NumberFormatException if the string cannot be parsed * as an integer. */ public static Integer valueOf(String s) throws NumberFormatException { return Integer.valueOf(parseInt(s, 10)); } /** * Cache to support the object identity semantics of autoboxing for values between * -128 and 127 (inclusive) as required by JLS. * * The cache is initialized on first usage. The size of the cache * may be controlled by the {@code -XX:AutoBoxCacheMax=<size>} option. * During VM initialization, java.lang.Integer.IntegerCache.high property * may be set and saved in the private system properties in the * jdk.internal.misc.VM class. * * WARNING: The cache is archived with CDS and reloaded from the shared * archive at runtime. The archived cache (Integer[]) and Integer objects * reside in the closed archive heap regions. Care should be taken when * changing the implementation and the cache array should not be assigned * with new Integer object(s) after initialization. */ private static class IntegerCache { static final int low = -128; static final int high; static final Integer[] cache; static Integer[] archivedCache; static { // high value may be configured by property int h = 127; String integerCacheHighPropValue = VM.getSavedProperty("java.lang.Integer.IntegerCache.high"); if (integerCacheHighPropValue != null) { try { h = Math.max(parseInt(integerCacheHighPropValue), 127); // Maximum array size is Integer.MAX_VALUE h = Math.min(h, Integer.MAX_VALUE - (-low) - 1); } catch (NumberFormatException nfe) { // If the property cannot be parsed into an int, ignore it. } } high = h; // Load IntegerCache.archivedCache from archive, if possible VM.initializeFromArchive(IntegerCache.class); int size = (high - low) + 1; // Use the archived cache if it exists and is large enough if (archivedCache == null || size > archivedCache.length) { Integer[] c = new Integer[size]; int j = low; for (int i = 0; i < c.length; i++) { c[i] = new Integer(j++); } archivedCache = c; } cache = archivedCache; // range [-128, 127] must be interned (JLS7 5.1.7) assert IntegerCache.high >= 127; } private IntegerCache() { } } /** * Returns an {@code Integer} instance representing the specified * {@code int} value. If a new {@code Integer} instance is not * required, this method should generally be used in preference to * the constructor {@link #Integer(int)}, as this method is likely * to yield significantly better space and time performance by * caching frequently requested values. * * This method will always cache values in the range -128 to 127, * inclusive, and may cache other values outside of this range. * * @param i an {@code int} value. * @return an {@code Integer} instance representing {@code i}. * @since 1.5 */ @HotSpotIntrinsicCandidate public static Integer valueOf(int i) { if (i >= IntegerCache.low && i <= IntegerCache.high) return IntegerCache.cache[i + (-IntegerCache.low)]; return new Integer(i); } /** * The value of the {@code Integer}. * * @serial */ private final int value; /** * Constructs a newly allocated {@code Integer} object that * represents the specified {@code int} value. * * @param value the value to be represented by the * {@code Integer} object. * * @deprecated * It is rarely appropriate to use this constructor. The static factory * {@link #valueOf(int)} is generally a better choice, as it is * likely to yield significantly better space and time performance. */ @Deprecated(since = "9") public Integer(int value) { this.value = value; } /** * Constructs a newly allocated {@code Integer} object that * represents the {@code int} value indicated by the * {@code String} parameter. The string is converted to an * {@code int} value in exactly the manner used by the * {@code parseInt} method for radix 10. * * @param s the {@code String} to be converted to an {@code Integer}. * @throws NumberFormatException if the {@code String} does not * contain a parsable integer. * * @deprecated * It is rarely appropriate to use this constructor. * Use {@link #parseInt(String)} to convert a string to a * {@code int} primitive, or use {@link #valueOf(String)} * to convert a string to an {@code Integer} object. */ @Deprecated(since = "9") public Integer(String s) throws NumberFormatException { this.value = parseInt(s, 10); } /** * Returns the value of this {@code Integer} as a {@code byte} * after a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversion */ public byte byteValue() { return (byte) value; } /** * Returns the value of this {@code Integer} as a {@code short} * after a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversion */ public short shortValue() { return (short) value; } /** * Returns the value of this {@code Integer} as an * {@code int}. */ @HotSpotIntrinsicCandidate public int intValue() { return value; } /** * Returns the value of this {@code Integer} as a {@code long} * after a widening primitive conversion. * @jls 5.1.2 Widening Primitive Conversion * @see Integer#toUnsignedLong(int) */ public long longValue() { return (long) value; } /** * Returns the value of this {@code Integer} as a {@code float} * after a widening primitive conversion. * @jls 5.1.2 Widening Primitive Conversion */ public float floatValue() { return (float) value; } /** * Returns the value of this {@code Integer} as a {@code double} * after a widening primitive conversion. * @jls 5.1.2 Widening Primitive Conversion */ public double doubleValue() { return (double) value; } /** * Returns a {@code String} object representing this * {@code Integer}'s value. The value is converted to signed * decimal representation and returned as a string, exactly as if * the integer value were given as an argument to the {@link * java.lang.Integer#toString(int)} method. * * @return a string representation of the value of this object in * base 10. */ public String toString() { return toString(value); } /** * Returns a hash code for this {@code Integer}. * * @return a hash code value for this object, equal to the * primitive {@code int} value represented by this * {@code Integer} object. */ @Override public int hashCode() { return Integer.hashCode(value); } /** * Returns a hash code for an {@code int} value; compatible with * {@code Integer.hashCode()}. * * @param value the value to hash * @since 1.8 * * @return a hash code value for an {@code int} value. */ public static int hashCode(int value) { return value; } /** * Compares this object to the specified object. The result is * {@code true} if and only if the argument is not * {@code null} and is an {@code Integer} object that * contains the same {@code int} value as this object. * * @param obj the object to compare with. * @return {@code true} if the objects are the same; * {@code false} otherwise. */ public boolean equals(Object obj) { if (obj instanceof Integer) { return value == ((Integer) obj).intValue(); } return false; } /** * Determines the integer value of the system property with the * specified name. * * <p>The first argument is treated as the name of a system * property. System properties are accessible through the {@link * java.lang.System#getProperty(java.lang.String)} method. The * string value of this property is then interpreted as an integer * value using the grammar supported by {@link Integer#decode decode} and * an {@code Integer} object representing this value is returned. * * <p>If there is no property with the specified name, if the * specified name is empty or {@code null}, or if the property * does not have the correct numeric format, then {@code null} is * returned. * * <p>In other words, this method returns an {@code Integer} * object equal to the value of: * * <blockquote> * {@code getInteger(nm, null)} * </blockquote> * * @param nm property name. * @return the {@code Integer} value of the property. * @throws SecurityException for the same reasons as * {@link System#getProperty(String) System.getProperty} * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) */ public static Integer getInteger(String nm) { return getInteger(nm, null); } /** * Determines the integer value of the system property with the * specified name. * * <p>The first argument is treated as the name of a system * property. System properties are accessible through the {@link * java.lang.System#getProperty(java.lang.String)} method. The * string value of this property is then interpreted as an integer * value using the grammar supported by {@link Integer#decode decode} and * an {@code Integer} object representing this value is returned. * * <p>The second argument is the default value. An {@code Integer} object * that represents the value of the second argument is returned if there * is no property of the specified name, if the property does not have * the correct numeric format, or if the specified name is empty or * {@code null}. * * <p>In other words, this method returns an {@code Integer} object * equal to the value of: * * <blockquote> * {@code getInteger(nm, new Integer(val))} * </blockquote> * * but in practice it may be implemented in a manner such as: * * <blockquote><pre> * Integer result = getInteger(nm, null); * return (result == null) ? new Integer(val) : result; * </pre></blockquote> * * to avoid the unnecessary allocation of an {@code Integer} * object when the default value is not needed. * * @param nm property name. * @param val default value. * @return the {@code Integer} value of the property. * @throws SecurityException for the same reasons as * {@link System#getProperty(String) System.getProperty} * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) */ public static Integer getInteger(String nm, int val) { Integer result = getInteger(nm, null); return (result == null) ? Integer.valueOf(val) : result; } /** * Returns the integer value of the system property with the * specified name. The first argument is treated as the name of a * system property. System properties are accessible through the * {@link java.lang.System#getProperty(java.lang.String)} method. * The string value of this property is then interpreted as an * integer value, as per the {@link Integer#decode decode} method, * and an {@code Integer} object representing this value is * returned; in summary: * * <ul><li>If the property value begins with the two ASCII characters * {@code 0x} or the ASCII character {@code #}, not * followed by a minus sign, then the rest of it is parsed as a * hexadecimal integer exactly as by the method * {@link #valueOf(java.lang.String, int)} with radix 16. * <li>If the property value begins with the ASCII character * {@code 0} followed by another character, it is parsed as an * octal integer exactly as by the method * {@link #valueOf(java.lang.String, int)} with radix 8. * <li>Otherwise, the property value is parsed as a decimal integer * exactly as by the method {@link #valueOf(java.lang.String, int)} * with radix 10. * </ul> * * <p>The second argument is the default value. The default value is * returned if there is no property of the specified name, if the * property does not have the correct numeric format, or if the * specified name is empty or {@code null}. * * @param nm property name. * @param val default value. * @return the {@code Integer} value of the property. * @throws SecurityException for the same reasons as * {@link System#getProperty(String) System.getProperty} * @see System#getProperty(java.lang.String) * @see System#getProperty(java.lang.String, java.lang.String) */ public static Integer getInteger(String nm, Integer val) { String v = null; try { v = System.getProperty(nm); } catch (IllegalArgumentException | NullPointerException e) { } if (v != null) { try { return Integer.decode(v); } catch (NumberFormatException e) { } } return val; } /** * Decodes a {@code String} into an {@code Integer}. * Accepts decimal, hexadecimal, and octal numbers given * by the following grammar: * * <blockquote> * <dl> * <dt><i>DecodableString:</i> * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> * * <dt><i>Sign:</i> * <dd>{@code -} * <dd>{@code +} * </dl> * </blockquote> * * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> * are as defined in section 3.10.1 of * <cite>The Java™ Language Specification</cite>, * except that underscores are not accepted between digits. * * <p>The sequence of characters following an optional * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", * "{@code #}", or leading zero) is parsed as by the {@code * Integer.parseInt} method with the indicated radix (10, 16, or * 8). This sequence of characters must represent a positive * value or a {@link NumberFormatException} will be thrown. The * result is negated if first character of the specified {@code * String} is the minus sign. No whitespace characters are * permitted in the {@code String}. * * @param nm the {@code String} to decode. * @return an {@code Integer} object holding the {@code int} * value represented by {@code nm} * @exception NumberFormatException if the {@code String} does not * contain a parsable integer. * @see java.lang.Integer#parseInt(java.lang.String, int) */ public static Integer decode(String nm) throws NumberFormatException { int radix = 10; int index = 0; boolean negative = false; Integer result; if (nm.isEmpty()) throw new NumberFormatException("Zero length string"); char firstChar = nm.charAt(0); // Handle sign, if present if (firstChar == '-') { negative = true; index++; } else if (firstChar == '+') index++; // Handle radix specifier, if present if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { index += 2; radix = 16; } else if (nm.startsWith("#", index)) { index++; radix = 16; } else if (nm.startsWith("0", index) && nm.length() > 1 + index) { index++; radix = 8; } if (nm.startsWith("-", index) || nm.startsWith("+", index)) throw new NumberFormatException("Sign character in wrong position"); try { result = Integer.valueOf(nm.substring(index), radix); result = negative ? Integer.valueOf(-result.intValue()) : result; } catch (NumberFormatException e) { // If number is Integer.MIN_VALUE, we'll end up here. The next line // handles this case, and causes any genuine format error to be // rethrown. String constant = negative ? ("-" + nm.substring(index)) : nm.substring(index); result = Integer.valueOf(constant, radix); } return result; } /** * Compares two {@code Integer} objects numerically. * * @param anotherInteger the {@code Integer} to be compared. * @return the value {@code 0} if this {@code Integer} is * equal to the argument {@code Integer}; a value less than * {@code 0} if this {@code Integer} is numerically less * than the argument {@code Integer}; and a value greater * than {@code 0} if this {@code Integer} is numerically * greater than the argument {@code Integer} (signed * comparison). * @since 1.2 */ public int compareTo(Integer anotherInteger) { return compare(this.value, anotherInteger.value); } /** * Compares two {@code int} values numerically. * The value returned is identical to what would be returned by: * <pre> * Integer.valueOf(x).compareTo(Integer.valueOf(y)) * </pre> * * @param x the first {@code int} to compare * @param y the second {@code int} to compare * @return the value {@code 0} if {@code x == y}; * a value less than {@code 0} if {@code x < y}; and * a value greater than {@code 0} if {@code x > y} * @since 1.7 */ public static int compare(int x, int y) { return (x < y) ? -1 : ((x == y) ? 0 : 1); } /** * Compares two {@code int} values numerically treating the values * as unsigned. * * @param x the first {@code int} to compare * @param y the second {@code int} to compare * @return the value {@code 0} if {@code x == y}; a value less * than {@code 0} if {@code x < y} as unsigned values; and * a value greater than {@code 0} if {@code x > y} as * unsigned values * @since 1.8 */ public static int compareUnsigned(int x, int y) { return compare(x + MIN_VALUE, y + MIN_VALUE); } /** * Converts the argument to a {@code long} by an unsigned * conversion. In an unsigned conversion to a {@code long}, the * high-order 32 bits of the {@code long} are zero and the * low-order 32 bits are equal to the bits of the integer * argument. * * Consequently, zero and positive {@code int} values are mapped * to a numerically equal {@code long} value and negative {@code * int} values are mapped to a {@code long} value equal to the * input plus 2<sup>32</sup>. * * @param x the value to convert to an unsigned {@code long} * @return the argument converted to {@code long} by an unsigned * conversion * @since 1.8 */ public static long toUnsignedLong(int x) { return ((long) x) & 0xffffffffL; } /** * Returns the unsigned quotient of dividing the first argument by * the second where each argument and the result is interpreted as * an unsigned value. * * <p>Note that in two's complement arithmetic, the three other * basic arithmetic operations of add, subtract, and multiply are * bit-wise identical if the two operands are regarded as both * being signed or both being unsigned. Therefore separate {@code * addUnsigned}, etc. methods are not provided. * * @param dividend the value to be divided * @param divisor the value doing the dividing * @return the unsigned quotient of the first argument divided by * the second argument * @see #remainderUnsigned * @since 1.8 */ public static int divideUnsigned(int dividend, int divisor) { // In lieu of tricky code, for now just use long arithmetic. return (int) (toUnsignedLong(dividend) / toUnsignedLong(divisor)); } /** * Returns the unsigned remainder from dividing the first argument * by the second where each argument and the result is interpreted * as an unsigned value. * * @param dividend the value to be divided * @param divisor the value doing the dividing * @return the unsigned remainder of the first argument divided by * the second argument * @see #divideUnsigned * @since 1.8 */ public static int remainderUnsigned(int dividend, int divisor) { // In lieu of tricky code, for now just use long arithmetic. return (int) (toUnsignedLong(dividend) % toUnsignedLong(divisor)); } // Bit twiddling /** * The number of bits used to represent an {@code int} value in two's * complement binary form. * * @since 1.5 */ @Native public static final int SIZE = 32; /** * The number of bytes used to represent an {@code int} value in two's * complement binary form. * * @since 1.8 */ public static final int BYTES = SIZE / Byte.SIZE; /** * Returns an {@code int} value with at most a single one-bit, in the * position of the highest-order ("leftmost") one-bit in the specified * {@code int} value. Returns zero if the specified value has no * one-bits in its two's complement binary representation, that is, if it * is equal to zero. * * @param i the value whose highest one bit is to be computed * @return an {@code int} value with a single one-bit, in the position * of the highest-order one-bit in the specified value, or zero if * the specified value is itself equal to zero. * @since 1.5 */ public static int highestOneBit(int i) { return i & (MIN_VALUE >>> numberOfLeadingZeros(i)); } /** * Returns an {@code int} value with at most a single one-bit, in the * position of the lowest-order ("rightmost") one-bit in the specified * {@code int} value. Returns zero if the specified value has no * one-bits in its two's complement binary representation, that is, if it * is equal to zero. * * @param i the value whose lowest one bit is to be computed * @return an {@code int} value with a single one-bit, in the position * of the lowest-order one-bit in the specified value, or zero if * the specified value is itself equal to zero. * @since 1.5 */ public static int lowestOneBit(int i) { // HD, Section 2-1 return i & -i; } /** * Returns the number of zero bits preceding the highest-order * ("leftmost") one-bit in the two's complement binary representation * of the specified {@code int} value. Returns 32 if the * specified value has no one-bits in its two's complement representation, * in other words if it is equal to zero. * * <p>Note that this method is closely related to the logarithm base 2. * For all positive {@code int} values x: * <ul> * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)} * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)} * </ul> * * @param i the value whose number of leading zeros is to be computed * @return the number of zero bits preceding the highest-order * ("leftmost") one-bit in the two's complement binary representation * of the specified {@code int} value, or 32 if the value * is equal to zero. * @since 1.5 */ @HotSpotIntrinsicCandidate public static int numberOfLeadingZeros(int i) { // HD, Count leading 0's if (i <= 0) return i == 0 ? 32 : 0; int n = 31; if (i >= 1 << 16) { n -= 16; i >>>= 16; } if (i >= 1 << 8) { n -= 8; i >>>= 8; } if (i >= 1 << 4) { n -= 4; i >>>= 4; } if (i >= 1 << 2) { n -= 2; i >>>= 2; } return n - (i >>> 1); } /** * Returns the number of zero bits following the lowest-order ("rightmost") * one-bit in the two's complement binary representation of the specified * {@code int} value. Returns 32 if the specified value has no * one-bits in its two's complement representation, in other words if it is * equal to zero. * * @param i the value whose number of trailing zeros is to be computed * @return the number of zero bits following the lowest-order ("rightmost") * one-bit in the two's complement binary representation of the * specified {@code int} value, or 32 if the value is equal * to zero. * @since 1.5 */ @HotSpotIntrinsicCandidate public static int numberOfTrailingZeros(int i) { // HD, Count trailing 0's i = ~i & (i - 1); if (i <= 0) return i & 32; int n = 1; if (i > 1 << 16) { n += 16; i >>>= 16; } if (i > 1 << 8) { n += 8; i >>>= 8; } if (i > 1 << 4) { n += 4; i >>>= 4; } if (i > 1 << 2) { n += 2; i >>>= 2; } return n + (i >>> 1); } /** * Returns the number of one-bits in the two's complement binary * representation of the specified {@code int} value. This function is * sometimes referred to as the <i>population count</i>. * * @param i the value whose bits are to be counted * @return the number of one-bits in the two's complement binary * representation of the specified {@code int} value. * @since 1.5 */ @HotSpotIntrinsicCandidate public static int bitCount(int i) { // HD, Figure 5-2 i = i - ((i >>> 1) & 0x55555555); i = (i & 0x33333333) + ((i >>> 2) & 0x33333333); i = (i + (i >>> 4)) & 0x0f0f0f0f; i = i + (i >>> 8); i = i + (i >>> 16); return i & 0x3f; } /** * Returns the value obtained by rotating the two's complement binary * representation of the specified {@code int} value left by the * specified number of bits. (Bits shifted out of the left hand, or * high-order, side reenter on the right, or low-order.) * * <p>Note that left rotation with a negative distance is equivalent to * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, * distance)}. Note also that rotation by any multiple of 32 is a * no-op, so all but the last five bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateLeft(val, * distance) == rotateLeft(val, distance & 0x1F)}. * * @param i the value whose bits are to be rotated left * @param distance the number of bit positions to rotate left * @return the value obtained by rotating the two's complement binary * representation of the specified {@code int} value left by the * specified number of bits. * @since 1.5 */ public static int rotateLeft(int i, int distance) { return (i << distance) | (i >>> -distance); } /** * Returns the value obtained by rotating the two's complement binary * representation of the specified {@code int} value right by the * specified number of bits. (Bits shifted out of the right hand, or * low-order, side reenter on the left, or high-order.) * * <p>Note that right rotation with a negative distance is equivalent to * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, * distance)}. Note also that rotation by any multiple of 32 is a * no-op, so all but the last five bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateRight(val, * distance) == rotateRight(val, distance & 0x1F)}. * * @param i the value whose bits are to be rotated right * @param distance the number of bit positions to rotate right * @return the value obtained by rotating the two's complement binary * representation of the specified {@code int} value right by the * specified number of bits. * @since 1.5 */ public static int rotateRight(int i, int distance) { return (i >>> distance) | (i << -distance); } /** * Returns the value obtained by reversing the order of the bits in the * two's complement binary representation of the specified {@code int} * value. * * @param i the value to be reversed * @return the value obtained by reversing order of the bits in the * specified {@code int} value. * @since 1.5 */ public static int reverse(int i) { // HD, Figure 7-1 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333; i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; return reverseBytes(i); } /** * Returns the signum function of the specified {@code int} value. (The * return value is -1 if the specified value is negative; 0 if the * specified value is zero; and 1 if the specified value is positive.) * * @param i the value whose signum is to be computed * @return the signum function of the specified {@code int} value. * @since 1.5 */ public static int signum(int i) { // HD, Section 2-7 return (i >> 31) | (-i >>> 31); } /** * Returns the value obtained by reversing the order of the bytes in the * two's complement representation of the specified {@code int} value. * * @param i the value whose bytes are to be reversed * @return the value obtained by reversing the bytes in the specified * {@code int} value. * @since 1.5 */ @HotSpotIntrinsicCandidate public static int reverseBytes(int i) { return (i << 24) | ((i & 0xff00) << 8) | ((i >>> 8) & 0xff00) | (i >>> 24); } /** * Adds two integers together as per the + operator. * * @param a the first operand * @param b the second operand * @return the sum of {@code a} and {@code b} * @see java.util.function.BinaryOperator * @since 1.8 */ public static int sum(int a, int b) { return a + b; } /** * Returns the greater of two {@code int} values * as if by calling {@link Math#max(int, int) Math.max}. * * @param a the first operand * @param b the second operand * @return the greater of {@code a} and {@code b} * @see java.util.function.BinaryOperator * @since 1.8 */ public static int max(int a, int b) { return Math.max(a, b); } /** * Returns the smaller of two {@code int} values * as if by calling {@link Math#min(int, int) Math.min}. * * @param a the first operand * @param b the second operand * @return the smaller of {@code a} and {@code b} * @see java.util.function.BinaryOperator * @since 1.8 */ public static int min(int a, int b) { return Math.min(a, b); } /** * Returns an {@link Optional} containing the nominal descriptor for this * instance, which is the instance itself. * * @return an {@link Optional} describing the {@linkplain Integer} instance * @since 12 */ @Override public Optional<Integer> describeConstable() { return Optional.of(this); } /** * Resolves this instance as a {@link ConstantDesc}, the result of which is * the instance itself. * * @param lookup ignored * @return the {@linkplain Integer} instance * @since 12 */ @Override public Integer resolveConstantDesc(MethodHandles.Lookup lookup) { return this; } /** use serialVersionUID from JDK 1.0.2 for interoperability */ @Native private static final long serialVersionUID = 1360826667806852920L; }