| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 java.lang; |
| |
| /** |
| * The wrapper for the primitive type {@code int}. |
| * <p> |
| * As with the specification, this implementation relies on code laid out in <a |
| * href="http://www.hackersdelight.org/">Henry S. Warren, Jr.'s Hacker's |
| * Delight, (Addison Wesley, 2002)</a> as well as <a |
| * href="http://aggregate.org/MAGIC/">The Aggregate's Magic Algorithms</a>. |
| * |
| * @see java.lang.Number |
| * @since 1.1 |
| */ |
| public final class Integer extends Number implements Comparable<Integer> { |
| |
| private static final long serialVersionUID = 1360826667806852920L; |
| |
| /** |
| * The value which the receiver represents. |
| */ |
| private final int value; |
| |
| /** |
| * Constant for the maximum {@code int} value, 2<sup>31</sup>-1. |
| */ |
| public static final int MAX_VALUE = 0x7FFFFFFF; |
| |
| /** |
| * Constant for the minimum {@code int} value, -2<sup>31</sup>. |
| */ |
| public static final int MIN_VALUE = 0x80000000; |
| |
| /** |
| * Constant for the number of bits needed to represent an {@code int} in |
| * two's complement form. |
| * |
| * @since 1.5 |
| */ |
| public static final int SIZE = 32; |
| |
| /* |
| * Progressively smaller decimal order of magnitude that can be represented |
| * by an instance of Integer. Used to help compute the String |
| * representation. |
| */ |
| private static final int[] decimalScale = new int[] { 1000000000, 100000000, |
| 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1 }; |
| |
| /** |
| * The {@link Class} object that represents the primitive type {@code int}. |
| */ |
| @SuppressWarnings("unchecked") |
| public static final Class<Integer> TYPE = (Class<Integer>) new int[0] |
| .getClass().getComponentType(); |
| |
| // Note: This can't be set to "int.class", since *that* is |
| // defined to be "java.lang.Integer.TYPE"; |
| |
| /** |
| * Constructs a new {@code Integer} with the specified primitive integer |
| * value. |
| * |
| * @param value |
| * the primitive integer value to store in the new instance. |
| */ |
| public Integer(int value) { |
| this.value = value; |
| } |
| |
| /** |
| * Constructs a new {@code Integer} from the specified string. |
| * |
| * @param string |
| * the string representation of an integer value. |
| * @throws NumberFormatException |
| * if {@code string} can not be decoded into an integer value. |
| * @see #parseInt(String) |
| */ |
| public Integer(String string) throws NumberFormatException { |
| this(parseInt(string)); |
| } |
| |
| @Override |
| public byte byteValue() { |
| return (byte) value; |
| } |
| |
| /** |
| * Compares this object to the specified integer object to determine their |
| * relative order. |
| * |
| * @param object |
| * the integer object to compare this object to. |
| * @return a negative value if the value of this integer is less than the |
| * value of {@code object}; 0 if the value of this integer and the |
| * value of {@code object} are equal; a positive value if the value |
| * of this integer is greater than the value of {@code object}. |
| * @see java.lang.Comparable |
| * @since 1.2 |
| */ |
| public int compareTo(Integer object) { |
| return value > object.value ? 1 : (value < object.value ? -1 : 0); |
| } |
| |
| /** |
| * Parses the specified string and returns a {@code Integer} instance if the |
| * string can be decoded into an integer value. The string may be an |
| * optional minus sign "-" followed by a hexadecimal ("0x..." or "#..."), |
| * octal ("0..."), or decimal ("...") representation of an integer. |
| * |
| * @param string |
| * a string representation of an integer value. |
| * @return an {@code Integer} containing the value represented by |
| * {@code string}. |
| * @throws NumberFormatException |
| * if {@code string} can not be parsed as an integer value. |
| */ |
| public static Integer decode(String string) throws NumberFormatException { |
| int length = string.length(), i = 0; |
| if (length == 0) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| char firstDigit = string.charAt(i); |
| boolean negative = firstDigit == '-'; |
| if (negative) { |
| if (length == 1) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| firstDigit = string.charAt(++i); |
| } |
| |
| int base = 10; |
| if (firstDigit == '0') { |
| if (++i == length) { |
| return valueOf(0); |
| } |
| if ((firstDigit = string.charAt(i)) == 'x' || firstDigit == 'X') { |
| if (++i == length) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| base = 16; |
| } else { |
| base = 8; |
| } |
| } else if (firstDigit == '#') { |
| if (++i == length) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| base = 16; |
| } |
| |
| int result = parse(string, i, base, negative); |
| return valueOf(result); |
| } |
| |
| @Override |
| public double doubleValue() { |
| return value; |
| } |
| |
| /** |
| * Compares this instance with the specified object and indicates if they |
| * are equal. In order to be equal, {@code o} must be an instance of |
| * {@code Integer} and have the same integer value as this object. |
| * |
| * @param o |
| * the object to compare this integer with. |
| * @return {@code true} if the specified object is equal to this |
| * {@code Integer}; {@code false} otherwise. |
| */ |
| @Override |
| public boolean equals(Object o) { |
| return (o instanceof Integer) |
| && (value == ((Integer) o).value); |
| } |
| |
| @Override |
| public float floatValue() { |
| return value; |
| } |
| |
| /** |
| * Returns the {@code Integer} value of the system property identified by |
| * {@code string}. Returns {@code null} if {@code string} is {@code null} |
| * or empty, if the property can not be found or if its value can not be |
| * parsed as an integer. |
| * |
| * @param string |
| * the name of the requested system property. |
| * @return the requested property's value as an {@code Integer} or |
| * {@code null}. |
| */ |
| public static Integer getInteger(String string) { |
| if (string == null || string.length() == 0) { |
| return null; |
| } |
| String prop = System.getProperty(string); |
| if (prop == null) { |
| return null; |
| } |
| try { |
| return decode(prop); |
| } catch (NumberFormatException ex) { |
| return null; |
| } |
| } |
| |
| /** |
| * Returns the {@code Integer} value of the system property identified by |
| * {@code string}. Returns the specified default value if {@code string} is |
| * {@code null} or empty, if the property can not be found or if its value |
| * can not be parsed as an integer. |
| * |
| * @param string |
| * the name of the requested system property. |
| * @param defaultValue |
| * the default value that is returned if there is no integer |
| * system property with the requested name. |
| * @return the requested property's value as an {@code Integer} or the |
| * default value. |
| */ |
| public static Integer getInteger(String string, int defaultValue) { |
| if (string == null || string.length() == 0) { |
| return valueOf(defaultValue); |
| } |
| String prop = System.getProperty(string); |
| if (prop == null) { |
| return valueOf(defaultValue); |
| } |
| try { |
| return decode(prop); |
| } catch (NumberFormatException ex) { |
| return valueOf(defaultValue); |
| } |
| } |
| |
| /** |
| * Returns the {@code Integer} value of the system property identified by |
| * {@code string}. Returns the specified default value if {@code string} is |
| * {@code null} or empty, if the property can not be found or if its value |
| * can not be parsed as an integer. |
| * |
| * @param string |
| * the name of the requested system property. |
| * @param defaultValue |
| * the default value that is returned if there is no integer |
| * system property with the requested name. |
| * @return the requested property's value as an {@code Integer} or the |
| * default value. |
| */ |
| public static Integer getInteger(String string, Integer defaultValue) { |
| if (string == null || string.length() == 0) { |
| return defaultValue; |
| } |
| String prop = System.getProperty(string); |
| if (prop == null) { |
| return defaultValue; |
| } |
| try { |
| return decode(prop); |
| } catch (NumberFormatException ex) { |
| return defaultValue; |
| } |
| } |
| |
| @Override |
| public int hashCode() { |
| return value; |
| } |
| |
| /** |
| * Gets the primitive value of this int. |
| * |
| * @return this object's primitive value. |
| */ |
| @Override |
| public int intValue() { |
| return value; |
| } |
| |
| @Override |
| public long longValue() { |
| return value; |
| } |
| |
| /** |
| * Parses the specified string as a signed decimal integer value. The ASCII |
| * character \u002d ('-') is recognized as the minus sign. |
| * |
| * @param string |
| * the string representation of an integer value. |
| * @return the primitive integer value represented by {@code string}. |
| * @throws NumberFormatException |
| * if {@code string} is {@code null}, has a length of zero or |
| * can not be parsed as an integer value. |
| */ |
| public static int parseInt(String string) throws NumberFormatException { |
| return parseInt(string, 10); |
| } |
| |
| /** |
| * Parses the specified string as a signed integer value using the specified |
| * radix. The ASCII character \u002d ('-') is recognized as the minus sign. |
| * |
| * @param string |
| * the string representation of an integer value. |
| * @param radix |
| * the radix to use when parsing. |
| * @return the primitive integer value represented by {@code string} using |
| * {@code radix}. |
| * @throws NumberFormatException |
| * if {@code string} is {@code null} or has a length of zero, |
| * {@code radix < Character.MIN_RADIX}, |
| * {@code radix > Character.MAX_RADIX}, or if {@code string} |
| * can not be parsed as an integer value. |
| */ |
| public static int parseInt(String string, int radix) |
| throws NumberFormatException { |
| if (string == null || radix < Character.MIN_RADIX |
| || radix > Character.MAX_RADIX) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| int length = string.length(), i = 0; |
| if (length == 0) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| boolean negative = string.charAt(i) == '-'; |
| if (negative && ++i == length) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| |
| return parse(string, i, radix, negative); |
| } |
| |
| private static int parse(String string, int offset, int radix, |
| boolean negative) throws NumberFormatException { |
| int max = Integer.MIN_VALUE / radix; |
| int result = 0, length = string.length(); |
| while (offset < length) { |
| int digit = Character.digit(string.charAt(offset++), radix); |
| if (digit == -1) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| if (max > result) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| int next = result * radix - digit; |
| if (next > result) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| result = next; |
| } |
| if (!negative) { |
| result = -result; |
| if (result < 0) { |
| // BEGIN android-changed |
| throw new NumberFormatException("unable to parse '"+string+"' as integer"); |
| // END android-changed |
| } |
| } |
| return result; |
| } |
| |
| @Override |
| public short shortValue() { |
| return (short) value; |
| } |
| |
| /** |
| * Converts the specified integer into its binary string representation. The |
| * returned string is a concatenation of '0' and '1' characters. |
| * |
| * @param i |
| * the integer to convert. |
| * @return the binary string representation of {@code i}. |
| */ |
| public static String toBinaryString(int i) { |
| int count = 1, j = i; |
| |
| if (i < 0) { |
| count = 32; |
| } else { |
| while ((j >>>= 1) != 0) { |
| count++; |
| } |
| } |
| |
| char[] buffer = new char[count]; |
| do { |
| buffer[--count] = (char) ((i & 1) + '0'); |
| i >>>= 1; |
| } while (count > 0); |
| return new String(0, buffer.length, buffer); |
| } |
| |
| /** |
| * Converts the specified integer into its hexadecimal string |
| * representation. The returned string is a concatenation of characters from |
| * '0' to '9' and 'a' to 'f'. |
| * |
| * @param i |
| * the integer to convert. |
| * @return the hexadecimal string representation of {@code i}. |
| */ |
| public static String toHexString(int i) { |
| int count = 1, j = i; |
| |
| if (i < 0) { |
| count = 8; |
| } else { |
| while ((j >>>= 4) != 0) { |
| count++; |
| } |
| } |
| |
| char[] buffer = new char[count]; |
| do { |
| int t = i & 15; |
| if (t > 9) { |
| t = t - 10 + 'a'; |
| } else { |
| t += '0'; |
| } |
| buffer[--count] = (char) t; |
| i >>>= 4; |
| } while (count > 0); |
| return new String(0, buffer.length, buffer); |
| } |
| |
| /** |
| * Converts the specified integer into its octal string representation. The |
| * returned string is a concatenation of characters from '0' to '7'. |
| * |
| * @param i |
| * the integer to convert. |
| * @return the octal string representation of {@code i}. |
| */ |
| public static String toOctalString(int i) { |
| int count = 1, j = i; |
| |
| if (i < 0) { |
| count = 11; |
| } else { |
| while ((j >>>= 3) != 0) { |
| count++; |
| } |
| } |
| |
| char[] buffer = new char[count]; |
| do { |
| buffer[--count] = (char) ((i & 7) + '0'); |
| i >>>= 3; |
| } while (count > 0); |
| return new String(0, buffer.length, buffer); |
| } |
| |
| @Override |
| public String toString() { |
| return Integer.toString(value); |
| } |
| |
| /** |
| * Converts the specified integer into its decimal string representation. |
| * The returned string is a concatenation of a minus sign if the number is |
| * negative and characters from '0' to '9'. |
| * |
| * @param value |
| * the integer to convert. |
| * @return the decimal string representation of {@code value}. |
| */ |
| public static String toString(int value) { |
| // BEGIN android-note |
| // cache the strings in the range 0..99 to save allocations? |
| // END android-note |
| if (value == 0) { |
| return "0"; //$NON-NLS-1$ |
| } |
| |
| // Faster algorithm for smaller Integers |
| if (value < 1000 && value > -1000) { |
| char[] buffer = new char[4]; |
| int positive_value = value < 0 ? -value : value; |
| int first_digit = 0; |
| if (value < 0) { |
| buffer[0] = '-'; |
| first_digit++; |
| } |
| int last_digit = first_digit; |
| int quot = positive_value; |
| do { |
| int res = quot / 10; |
| int digit_value = quot - ((res << 3) + (res << 1)); |
| digit_value += '0'; |
| buffer[last_digit++] = (char) digit_value; |
| quot = res; |
| } while (quot != 0); |
| |
| int count = last_digit--; |
| do { |
| char tmp = buffer[last_digit]; |
| buffer[last_digit--] = buffer[first_digit]; |
| buffer[first_digit++] = tmp; |
| } while (first_digit < last_digit); |
| return new String(0, count, buffer); |
| } |
| if (value == MIN_VALUE) { |
| return "-2147483648";//$NON-NLS-1$ |
| } |
| |
| char[] buffer = new char[11]; |
| int positive_value = value < 0 ? -value : value; |
| byte first_digit = 0; |
| if (value < 0) { |
| buffer[0] = '-'; |
| first_digit++; |
| } |
| byte last_digit = first_digit; |
| byte count; |
| int number; |
| boolean start = false; |
| for (int i = 0; i < 9; i++) { |
| count = 0; |
| if (positive_value < (number = decimalScale[i])) { |
| if (start) { |
| buffer[last_digit++] = '0'; |
| } |
| continue; |
| } |
| |
| if (i > 0) { |
| number = (decimalScale[i] << 3); |
| if (positive_value >= number) { |
| positive_value -= number; |
| count += 8; |
| } |
| number = (decimalScale[i] << 2); |
| if (positive_value >= number) { |
| positive_value -= number; |
| count += 4; |
| } |
| } |
| number = (decimalScale[i] << 1); |
| if (positive_value >= number) { |
| positive_value -= number; |
| count += 2; |
| } |
| if (positive_value >= decimalScale[i]) { |
| positive_value -= decimalScale[i]; |
| count++; |
| } |
| if (count > 0 && !start) { |
| start = true; |
| } |
| if (start) { |
| buffer[last_digit++] = (char) (count + '0'); |
| } |
| } |
| |
| buffer[last_digit++] = (char) (positive_value + '0'); |
| count = last_digit--; |
| return new String(0, count, buffer); |
| } |
| |
| /** |
| * Converts the specified integer into a string representation based on the |
| * specified radix. The returned string is a concatenation of a minus sign |
| * if the number is negative and characters from '0' to '9' and 'a' to 'z', |
| * depending on the radix. If {@code radix} is not in the interval defined |
| * by {@code Character.MIN_RADIX} and {@code Character.MAX_RADIX} then 10 is |
| * used as the base for the conversion. |
| * |
| * @param i |
| * the integer to convert. |
| * @param radix |
| * the base to use for the conversion. |
| * @return the string representation of {@code i}. |
| */ |
| public static String toString(int i, int radix) { |
| // BEGIN android-note |
| // if radix==10, call thru to faster Integer.toString(int) ? |
| // only worthwhile if 10 is a popular parameter |
| // END android-note |
| if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) { |
| radix = 10; |
| } |
| if (i == 0) { |
| return "0"; //$NON-NLS-1$ |
| } |
| |
| int count = 2, j = i; |
| boolean negative = i < 0; |
| if (!negative) { |
| count = 1; |
| j = -i; |
| } |
| while ((i /= radix) != 0) { |
| count++; |
| } |
| |
| char[] buffer = new char[count]; |
| do { |
| int ch = 0 - (j % radix); |
| if (ch > 9) { |
| ch = ch - 10 + 'a'; |
| } else { |
| ch += '0'; |
| } |
| buffer[--count] = (char) ch; |
| } while ((j /= radix) != 0); |
| if (negative) { |
| buffer[0] = '-'; |
| } |
| return new String(0, buffer.length, buffer); |
| } |
| |
| /** |
| * Parses the specified string as a signed decimal integer value. |
| * |
| * @param string |
| * the string representation of an integer value. |
| * @return an {@code Integer} instance containing the integer value |
| * represented by {@code string}. |
| * @throws NumberFormatException |
| * if {@code string} is {@code null}, has a length of zero or |
| * can not be parsed as an integer value. |
| * @see #parseInt(String) |
| */ |
| public static Integer valueOf(String string) throws NumberFormatException { |
| return valueOf(parseInt(string)); |
| } |
| |
| /** |
| * Parses the specified string as a signed integer value using the specified |
| * radix. |
| * |
| * @param string |
| * the string representation of an integer value. |
| * @param radix |
| * the radix to use when parsing. |
| * @return an {@code Integer} instance containing the integer value |
| * represented by {@code string} using {@code radix}. |
| * @throws NumberFormatException |
| * if {@code string} is {@code null} or has a length of zero, |
| * {@code radix < Character.MIN_RADIX}, |
| * {@code radix > Character.MAX_RADIX}, or if {@code string} |
| * can not be parsed as an integer value. |
| * @see #parseInt(String, int) |
| */ |
| public static Integer valueOf(String string, int radix) |
| throws NumberFormatException { |
| return valueOf(parseInt(string, radix)); |
| } |
| |
| /** |
| * Determines the highest (leftmost) bit of the specified integer that is 1 |
| * and returns the bit mask value for that bit. This is also referred to as |
| * the Most Significant 1 Bit. Returns zero if the specified integer is |
| * zero. |
| * |
| * @param i |
| * the integer to examine. |
| * @return the bit mask indicating the highest 1 bit in {@code i}. |
| * @since 1.5 |
| */ |
| public static int highestOneBit(int i) { |
| i |= (i >> 1); |
| i |= (i >> 2); |
| i |= (i >> 4); |
| i |= (i >> 8); |
| i |= (i >> 16); |
| return (i & ~(i >>> 1)); |
| } |
| |
| /** |
| * Determines the lowest (rightmost) bit of the specified integer that is 1 |
| * and returns the bit mask value for that bit. This is also referred |
| * to as the Least Significant 1 Bit. Returns zero if the specified integer |
| * is zero. |
| * |
| * @param i |
| * the integer to examine. |
| * @return the bit mask indicating the lowest 1 bit in {@code i}. |
| * @since 1.5 |
| */ |
| public static int lowestOneBit(int i) { |
| return (i & (-i)); |
| } |
| |
| /** |
| * Determines the number of leading zeros in the specified integer prior to |
| * the {@link #highestOneBit(int) highest one bit}. |
| * |
| * @param i |
| * the integer to examine. |
| * @return the number of leading zeros in {@code i}. |
| * @since 1.5 |
| */ |
| public static int numberOfLeadingZeros(int i) { |
| i |= i >> 1; |
| i |= i >> 2; |
| i |= i >> 4; |
| i |= i >> 8; |
| i |= i >> 16; |
| return bitCount(~i); |
| } |
| |
| /** |
| * Determines the number of trailing zeros in the specified integer after |
| * the {@link #lowestOneBit(int) lowest one bit}. |
| * |
| * @param i |
| * the integer to examine. |
| * @return the number of trailing zeros in {@code i}. |
| * @since 1.5 |
| */ |
| public static int numberOfTrailingZeros(int i) { |
| return bitCount((i & -i) - 1); |
| } |
| |
| /** |
| * Counts the number of 1 bits in the specified integer; this is also |
| * referred to as population count. |
| * |
| * @param i |
| * the integer to examine. |
| * @return the number of 1 bits in {@code i}. |
| * @since 1.5 |
| */ |
| public static int bitCount(int i) { |
| i -= ((i >> 1) & 0x55555555); |
| i = (i & 0x33333333) + ((i >> 2) & 0x33333333); |
| i = (((i >> 4) + i) & 0x0F0F0F0F); |
| i += (i >> 8); |
| i += (i >> 16); |
| return (i & 0x0000003F); |
| } |
| |
| /** |
| * Rotates the bits of the specified integer to the left by the specified |
| * number of bits. |
| * |
| * @param i |
| * the integer value to rotate left. |
| * @param distance |
| * the number of bits to rotate. |
| * @return the rotated value. |
| * @since 1.5 |
| */ |
| public static int rotateLeft(int i, int distance) { |
| if (distance == 0) { |
| return i; |
| } |
| /* |
| * According to JLS3, 15.19, the right operand of a shift is always |
| * implicitly masked with 0x1F, which the negation of 'distance' is |
| * taking advantage of. |
| */ |
| return ((i << distance) | (i >>> (-distance))); |
| } |
| |
| /** |
| * Rotates the bits of the specified integer to the right by the specified |
| * number of bits. |
| * |
| * @param i |
| * the integer value to rotate right. |
| * @param distance |
| * the number of bits to rotate. |
| * @return the rotated value. |
| * @since 1.5 |
| */ |
| public static int rotateRight(int i, int distance) { |
| if (distance == 0) { |
| return i; |
| } |
| /* |
| * According to JLS3, 15.19, the right operand of a shift is always |
| * implicitly masked with 0x1F, which the negation of 'distance' is |
| * taking advantage of. |
| */ |
| return ((i >>> distance) | (i << (-distance))); |
| } |
| |
| /** |
| * Reverses the order of the bytes of the specified integer. |
| * |
| * @param i |
| * the integer value for which to reverse the byte order. |
| * @return the reversed value. |
| * @since 1.5 |
| */ |
| public static int reverseBytes(int i) { |
| int b3 = i >>> 24; |
| int b2 = (i >>> 8) & 0xFF00; |
| int b1 = (i & 0xFF00) << 8; |
| int b0 = i << 24; |
| return (b0 | b1 | b2 | b3); |
| } |
| |
| /** |
| * Reverses the order of the bits of the specified integer. |
| * |
| * @param i |
| * the integer value for which to reverse the bit order. |
| * @return the reversed value. |
| * @since 1.5 |
| */ |
| public static int reverse(int i) { |
| // From Hacker's Delight, 7-1, 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 value of the {@code signum} function for the specified |
| * integer. |
| * |
| * @param i |
| * the integer value to check. |
| * @return -1 if {@code i} is negative, 1 if {@code i} is positive, 0 if |
| * {@code i} is zero. |
| * @since 1.5 |
| */ |
| public static int signum(int i) { |
| return (i == 0 ? 0 : (i < 0 ? -1 : 1)); |
| } |
| |
| /** |
| * Returns a {@code Integer} instance for the specified integer value. |
| * <p> |
| * If it is not necessary to get a new {@code Integer} instance, it is |
| * recommended to use this method instead of the constructor, since it |
| * maintains a cache of instances which may result in better performance. |
| * |
| * @param i |
| * the integer value to store in the instance. |
| * @return a {@code Integer} instance containing {@code i}. |
| * @since 1.5 |
| */ |
| public static Integer valueOf(int i) { |
| if (i < -128 || i > 127) { |
| return new Integer(i); |
| } |
| return valueOfCache.CACHE [i+128]; |
| |
| } |
| |
| static class valueOfCache { |
| /** |
| * <p> |
| * A cache of instances used by {@link Integer#valueOf(int)} and auto-boxing. |
| */ |
| static final Integer[] CACHE = new Integer[256]; |
| |
| static { |
| for(int i=-128; i<=127; i++) { |
| CACHE[i+128] = new Integer(i); |
| } |
| } |
| } |
| } |
