In addition, this class provides several methods for converting * a {@code long} to a {@code String} and a {@code String} to a {@code * long}, as well as other constants and methods useful when dealing * with a {@code long}. * *

Implementation note: The implementations of the "bit twiddling" * methods (such as {@link #highestOneBit(long) highestOneBit} and * {@link #numberOfTrailingZeros(long) numberOfTrailingZeros}) are * based on material from Henry S. Warren, Jr.'s Hacker's * Delight, (Addison Wesley, 2002). * * @author Lee Boynton * @author Arthur van Hoff * @author Josh Bloch * @author Joseph D. Darcy * @since JDK1.0 */ public final class Long extends Number implements Comparable { /** * A constant holding the minimum value a {@code long} can * have, -2⁶³. */ @Native public static final long MIN_VALUE = 0x8000000000000000L; /** * A constant holding the maximum value a {@code long} can * have, 2⁶³-1. */ @Native public static final long MAX_VALUE = 0x7fffffffffffffffL; /** * The {@code Class} instance representing the primitive type * {@code long}. * * @since JDK1.1 */ @SuppressWarnings("unchecked") public static final Class TYPE = (Class) Class.getPrimitiveClass("long"); /** * Returns a string representation of the first argument in the * radix specified by the second argument. * *

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. * *

If the first argument is negative, the first element of the * result is the ASCII minus sign {@code '-'} * ({@code '\u005Cu002d'}). If the first argument is not * negative, no sign character appears in the result. * *

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: * *

* {@code 0123456789abcdefghijklmnopqrstuvwxyz} *

* {@code Long.toString(n, 16).toUpperCase()} *

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. * *

Note that since the first argument is treated as an unsigned * value, no leading sign character is printed. * *

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 behavior of radixes and the characters used as digits * are the same as {@link #toString(long, 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(long, int) * @since 1.8 */ public static String toUnsignedString(long i, int radix) { if (i >= 0) return toString(i, radix); else { switch (radix) { case 2: return toBinaryString(i); case 4: return toUnsignedString0(i, 2); case 8: return toOctalString(i); case 10: /* * We can get the effect of an unsigned division by 10 * on a long value by first shifting right, yielding a * positive value, and then dividing by 5. This * allows the last digit and preceding digits to be * isolated more quickly than by an initial conversion * to BigInteger. */ long quot = (i >>> 1) / 5; long rem = i - quot * 10; return toString(quot) + rem; case 16: return toHexString(i); case 32: return toUnsignedString0(i, 5); default: return toUnsignedBigInteger(i).toString(radix); } } } /** * Return a BigInteger equal to the unsigned value of the * argument. */ private static BigInteger toUnsignedBigInteger(long i) { if (i >= 0L) return BigInteger.valueOf(i); else { int upper = (int) (i >>> 32); int lower = (int) i; // return (upper << 32) + lower return (BigInteger.valueOf(Integer.toUnsignedLong(upper))).shiftLeft(32). add(BigInteger.valueOf(Integer.toUnsignedLong(lower))); } } /** * Returns a string representation of the {@code long} * argument as an unsigned integer in base 16. * *

The unsigned {@code long} value is the argument plus * 2⁶⁴ 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. * *

The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, * 16)}. * *

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: * *

* {@code 0123456789abcdef} *

* {@code Long.toHexString(n).toUpperCase()} *

The unsigned {@code long} value is the argument plus * 2⁶⁴ 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. * *

The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, * 8)}. * *

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: * *

* {@code 01234567} *

The unsigned {@code long} value is the argument plus * 2⁶⁴ 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. * *

The value of the argument can be recovered from the returned * string {@code s} by calling {@link * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, * 2)}. * *

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 a {@code long} to be converted to a string. * @return the string representation of the unsigned {@code long} * value represented by the argument in binary (base 2). * @see #parseUnsignedLong(String, int) * @see #toUnsignedString(long, int) * @since JDK 1.0.2 */ public static String toBinaryString(long i) { return toUnsignedString0(i, 1); } /** * Format a long (treated as unsigned) into a String. * @param val the value to format * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) */ static String toUnsignedString0(long val, int shift) { // assert shift > 0 && shift <=5 : "Illegal shift value"; int mag = Long.SIZE - Long.numberOfLeadingZeros(val); int chars = Math.max(((mag + (shift - 1)) / shift), 1); char[] buf = new char[chars]; formatUnsignedLong(val, shift, buf, 0, chars); return new String(buf, true); } /** * Format a long (treated as unsigned) into a character buffer. * @param val the unsigned long 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 * @return the lowest character location used */ static int formatUnsignedLong(long val, int shift, char[] buf, int offset, int len) { int charPos = len; int radix = 1 << shift; int mask = radix - 1; do { buf[offset + --charPos] = Integer.digits[((int) val) & mask]; val >>>= shift; } while (val != 0 && charPos > 0); return charPos; } /** * Returns a {@code String} object representing the specified * {@code long}. The argument is converted to signed decimal * representation and returned as a string, exactly as if the * argument and the radix 10 were given as arguments to the {@link * #toString(long, int)} method. * * @param i a {@code long} to be converted. * @return a string representation of the argument in base 10. */ public static String toString(long i) { if (i == Long.MIN_VALUE) return "-9223372036854775808"; int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); char[] buf = new char[size]; getChars(i, size, buf); return new String(buf, true); } /** * 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(long, * int)} method. * * @param i an integer to be converted to an unsigned string. * @return an unsigned string representation of the argument. * @see #toUnsignedString(long, int) * @since 1.8 */ public static String toUnsignedString(long i) { return toUnsignedString(i, 10); } /** * 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. * * Will fail if i == Long.MIN_VALUE */ static void getChars(long i, int index, char[] buf) { long q; int r; int charPos = index; char sign = 0; if (i < 0) { sign = '-'; i = -i; } // Get 2 digits/iteration using longs until quotient fits into an int while (i > Integer.MAX_VALUE) { q = i / 100; // really: r = i - (q * 100); r = (int)(i - ((q << 6) + (q << 5) + (q << 2))); i = q; buf[--charPos] = Integer.DigitOnes[r]; buf[--charPos] = Integer.DigitTens[r]; } // Get 2 digits/iteration using ints int q2; int i2 = (int)i; while (i2 >= 65536) { q2 = i2 / 100; // really: r = i2 - (q * 100); r = i2 - ((q2 << 6) + (q2 << 5) + (q2 << 2)); i2 = q2; buf[--charPos] = Integer.DigitOnes[r]; buf[--charPos] = Integer.DigitTens[r]; } // Fall thru to fast mode for smaller numbers // assert(i2 <= 65536, i2); for (;;) { q2 = (i2 * 52429) >>> (16+3); r = i2 - ((q2 << 3) + (q2 << 1)); // r = i2-(q2*10) ... buf[--charPos] = Integer.digits[r]; i2 = q2; if (i2 == 0) break; } if (sign != 0) { buf[--charPos] = sign; } } // Requires positive x static int stringSize(long x) { long p = 10; for (int i=1; i<19; i++) { if (x < p) return i; p = 10*p; } return 19; } /** * Parses the string argument as a signed {@code long} 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 {@code long} value is returned. * *

Note that neither the character {@code L} * ({@code '\u005Cu004C'}) nor {@code l} * ({@code '\u005Cu006C'}) is permitted to appear at the end * of the string as a type indicator, as would be permitted in * Java programming language source code - except that either * {@code L} or {@code l} may appear as a digit for a * radix greater than or equal to 22. * *

An exception of type {@code NumberFormatException} is * thrown if any of the following situations occurs: *

* *
• The first argument is {@code null} or is a string of * length zero. * *
• The {@code radix} is either smaller than {@link * java.lang.Character#MIN_RADIX} or larger than {@link * java.lang.Character#MAX_RADIX}. * *
• 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. * *
• The value represented by the string is not a value of type * {@code long}. *

Examples: *

     * parseLong("0", 10) returns 0L
     * parseLong("473", 10) returns 473L
     * parseLong("+42", 10) returns 42L
     * parseLong("-0", 10) returns 0L
     * parseLong("-FF", 16) returns -255L
     * parseLong("1100110", 2) returns 102L
     * parseLong("99", 8) throws a NumberFormatException
     * parseLong("Hazelnut", 10) throws a NumberFormatException
     * parseLong("Hazelnut", 36) returns 1356099454469L
     * 

Note that neither the character {@code L} * ({@code '\u005Cu004C'}) nor {@code l} * ({@code '\u005Cu006C'}) is permitted to appear at the end * of the string as a type indicator, as would be permitted in * Java programming language source code. * * @param s a {@code String} containing the {@code long} * representation to be parsed * @return the {@code long} represented by the argument in * decimal. * @throws NumberFormatException if the string does not contain a * parsable {@code long}. */ public static long parseLong(String s) throws NumberFormatException { return parseLong(s, 10); } /** * Parses the string argument as an unsigned {@code long} 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. * *

An exception of type {@code NumberFormatException} is * thrown if any of the following situations occurs: *

*
• The first argument is {@code null} or is a string of * length zero. * *
• The radix is either smaller than * {@link java.lang.Character#MIN_RADIX} or * larger than {@link java.lang.Character#MAX_RADIX}. * *
• 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. * *
• The value represented by the string is larger than the * largest unsigned {@code long}, 2⁶⁴-1. * *

In other words, this method returns a {@code Long} object equal * to the value of: * *

* {@code new Long(Long.parseLong(s, radix))} *

In other words, this method returns a {@code Long} object * equal to the value of: * *

* {@code new Long(Long.parseLong(s))} *

*

*

DecodableString: *

Sign_opt DecimalNumeral *

Sign_opt {@code 0x} HexDigits *

Sign_opt {@code 0X} HexDigits *

Sign_opt {@code #} HexDigits *

Sign_opt {@code 0} OctalDigits * *

Sign: *

{@code -} *

{@code +} *

*

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 * Long.parseLong} 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 a {@code Long} object holding the {@code long} * value represented by {@code nm} * @throws NumberFormatException if the {@code String} does not * contain a parsable {@code long}. * @see java.lang.Long#parseLong(String, int) * @since 1.2 */ public static Long decode(String nm) throws NumberFormatException { int radix = 10; int index = 0; boolean negative = false; Long result; if (nm.length() == 0) 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 = Long.valueOf(nm.substring(index), radix); result = negative ? Long.valueOf(-result.longValue()) : result; } catch (NumberFormatException e) { // If number is Long.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 = Long.valueOf(constant, radix); } return result; } /** * The value of the {@code Long}. * * @serial */ private final long value; /** * Constructs a newly allocated {@code Long} object that * represents the specified {@code long} argument. * * @param value the value to be represented by the * {@code Long} object. */ public Long(long value) { this.value = value; } /** * Constructs a newly allocated {@code Long} object that * represents the {@code long} value indicated by the * {@code String} parameter. The string is converted to a * {@code long} value in exactly the manner used by the * {@code parseLong} method for radix 10. * * @param s the {@code String} to be converted to a * {@code Long}. * @throws NumberFormatException if the {@code String} does not * contain a parsable {@code long}. * @see java.lang.Long#parseLong(java.lang.String, int) */ public Long(String s) throws NumberFormatException { this.value = parseLong(s, 10); } /** * Returns the value of this {@code Long} as a {@code byte} after * a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversions */ public byte byteValue() { return (byte)value; } /** * Returns the value of this {@code Long} as a {@code short} after * a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversions */ public short shortValue() { return (short)value; } /** * Returns the value of this {@code Long} as an {@code int} after * a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversions */ public int intValue() { return (int)value; } /** * Returns the value of this {@code Long} as a * {@code long} value. */ public long longValue() { return value; } /** * Returns the value of this {@code Long} as a {@code float} after * a widening primitive conversion. * @jls 5.1.2 Widening Primitive Conversions */ public float floatValue() { return (float)value; } /** * Returns the value of this {@code Long} as a {@code double} * after a widening primitive conversion. * @jls 5.1.2 Widening Primitive Conversions */ public double doubleValue() { return (double)value; } /** * Returns a {@code String} object representing this * {@code Long}'s value. The value is converted to signed * decimal representation and returned as a string, exactly as if * the {@code long} value were given as an argument to the * {@link java.lang.Long#toString(long)} 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 Long}. The result is * the exclusive OR of the two halves of the primitive * {@code long} value held by this {@code Long} * object. That is, the hashcode is the value of the expression: * *

* {@code (int)(this.longValue()^(this.longValue()>>>32))} *

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 a {@code * long} value using the grammar supported by {@link Long#decode decode} * and a {@code Long} object representing this value is returned. * *

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. * *

In other words, this method returns a {@code Long} object * equal to the value of: * *

* {@code getLong(nm, null)} *

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 a {@code * long} value using the grammar supported by {@link Long#decode decode} * and a {@code Long} object representing this value is returned. * *

The second argument is the default value. A {@code Long} 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 null. * *

In other words, this method returns a {@code Long} object equal * to the value of: * *

* {@code getLong(nm, new Long(val))} *

     * Long result = getLong(nm, null);
     * return (result == null) ? new Long(val) : result;
     * 

*
• 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 for the method {@link #valueOf(java.lang.String, int)} * with radix 16. *
• 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. *
• Otherwise the property value is parsed as a decimal * integer exactly as by the method * {@link #valueOf(java.lang.String, int)} with radix 10. *

Note that, in every case, neither {@code L} * ({@code '\u005Cu004C'}) nor {@code l} * ({@code '\u005Cu006C'}) is permitted to appear at the end * of the property value as a type indicator, as would be * permitted in Java programming language source code. * *

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 Long} 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 Long getLong(String nm, Long val) { String v = null; try { v = System.getProperty(nm); } catch (IllegalArgumentException | NullPointerException e) { } if (v != null) { try { return Long.decode(v); } catch (NumberFormatException e) { } } return val; } /** * Compares two {@code Long} objects numerically. * * @param anotherLong the {@code Long} to be compared. * @return the value {@code 0} if this {@code Long} is * equal to the argument {@code Long}; a value less than * {@code 0} if this {@code Long} is numerically less * than the argument {@code Long}; and a value greater * than {@code 0} if this {@code Long} is numerically * greater than the argument {@code Long} (signed * comparison). * @since 1.2 */ public int compareTo(Long anotherLong) { return compare(this.value, anotherLong.value); } /** * Compares two {@code long} values numerically. * The value returned is identical to what would be returned by: *

     *    Long.valueOf(x).compareTo(Long.valueOf(y))
     * 

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 long divideUnsigned(long dividend, long divisor) { if (divisor < 0L) { // signed comparison // Answer must be 0 or 1 depending on relative magnitude // of dividend and divisor. return (compareUnsigned(dividend, divisor)) < 0 ? 0L :1L; } if (dividend > 0) // Both inputs non-negative return dividend/divisor; else { /* * For simple code, leveraging BigInteger. Longer and faster * code written directly in terms of operations on longs is * possible; see "Hacker's Delight" for divide and remainder * algorithms. */ return toUnsignedBigInteger(dividend). divide(toUnsignedBigInteger(divisor)).longValue(); } } /** * 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 long remainderUnsigned(long dividend, long divisor) { if (dividend > 0 && divisor > 0) { // signed comparisons return dividend % divisor; } else { if (compareUnsigned(dividend, divisor) < 0) // Avoid explicit check for 0 divisor return dividend; else return toUnsignedBigInteger(dividend). remainder(toUnsignedBigInteger(divisor)).longValue(); } } // Bit Twiddling /** * The number of bits used to represent a {@code long} value in two's * complement binary form. * * @since 1.5 */ @Native public static final int SIZE = 64; /** * The number of bytes used to represent a {@code long} value in two's * complement binary form. * * @since 1.8 */ public static final int BYTES = SIZE / Byte.SIZE; /** * Returns a {@code long} value with at most a single one-bit, in the * position of the highest-order ("leftmost") one-bit in the specified * {@code long} 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 a {@code long} 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 long highestOneBit(long i) { // HD, Figure 3-1 i |= (i >> 1); i |= (i >> 2); i |= (i >> 4); i |= (i >> 8); i |= (i >> 16); i |= (i >> 32); return i - (i >>> 1); } /** * Returns a {@code long} value with at most a single one-bit, in the * position of the lowest-order ("rightmost") one-bit in the specified * {@code long} 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 a {@code long} 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 long lowestOneBit(long 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 long} value. Returns 64 if the * specified value has no one-bits in its two's complement representation, * in other words if it is equal to zero. * *

Note that this method is closely related to the logarithm base 2. * For all positive {@code long} values x: *

*
• floor(log₂(x)) = {@code 63 - numberOfLeadingZeros(x)} *
• ceil(log₂(x)) = {@code 64 - numberOfLeadingZeros(x - 1)} *

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 64 is a * no-op, so all but the last six bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateLeft(val, * distance) == rotateLeft(val, distance & 0x3F)}. * * @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 long} value left by the * specified number of bits. * @since 1.5 */ public static long rotateLeft(long i, int distance) { return (i << distance) | (i >>> -distance); } /** * Returns the value obtained by rotating the two's complement binary * representation of the specified {@code long} 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.) * *

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 64 is a * no-op, so all but the last six bits of the rotation distance can be * ignored, even if the distance is negative: {@code rotateRight(val, * distance) == rotateRight(val, distance & 0x3F)}. * * @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 long} value right by the * specified number of bits. * @since 1.5 */ public static long rotateRight(long 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 long} * value. * * @param i the value to be reversed * @return the value obtained by reversing order of the bits in the * specified {@code long} value. * @since 1.5 */ public static long reverse(long i) { // HD, Figure 7-1 i = (i & 0x5555555555555555L) << 1 | (i >>> 1) & 0x5555555555555555L; i = (i & 0x3333333333333333L) << 2 | (i >>> 2) & 0x3333333333333333L; i = (i & 0x0f0f0f0f0f0f0f0fL) << 4 | (i >>> 4) & 0x0f0f0f0f0f0f0f0fL; i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; i = (i << 48) | ((i & 0xffff0000L) << 16) | ((i >>> 16) & 0xffff0000L) | (i >>> 48); return i; } /** * Returns the signum function of the specified {@code long} 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 long} value. * @since 1.5 */ public static int signum(long i) { // HD, Section 2-7 return (int) ((i >> 63) | (-i >>> 63)); } /** * Returns the value obtained by reversing the order of the bytes in the * two's complement representation of the specified {@code long} value. * * @param i the value whose bytes are to be reversed * @return the value obtained by reversing the bytes in the specified * {@code long} value. * @since 1.5 */ public static long reverseBytes(long i) { i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; return (i << 48) | ((i & 0xffff0000L) << 16) | ((i >>> 16) & 0xffff0000L) | (i >>> 48); } /** * Adds two {@code long} values 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 long sum(long a, long b) { return a + b; } /** * Returns the greater of two {@code long} values * as if by calling {@link Math#max(long, long) 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 long max(long a, long b) { return Math.max(a, b); } /** * Returns the smaller of two {@code long} values * as if by calling {@link Math#min(long, long) 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 long min(long a, long b) { return Math.min(a, b); } /** use serialVersionUID from JDK 1.0.2 for interoperability */ @Native private static final long serialVersionUID = 4290774380558885855L; }