- 总体阅读了Long的源码，基本跟Integer类类似，所以特别全部贴出源码，直接注释进行理解。
// final修饰符
public final class Long extends Number implements Comparable<Long> {
/**
* A constant holding the minimum value a {@code long} can
* have, -2<sup>63</sup>.
*/
// 最小值-负值
@Native public static final long MIN_VALUE = 0x8000000000000000L; /**
* A constant holding the maximum value a {@code long} can
* have, 2<sup>63</sup>-1.
*/
// 最大值-有符号
@Native public static final long MAX_VALUE = 0x7fffffffffffffffL; /**
* The {@code Class} instance representing the primitive type
* {@code long}.
*
* @since JDK1.1
*/
@SuppressWarnings("unchecked")
// class
public static final Class<Long> TYPE = (Class<Long>) Class.getPrimitiveClass("long"); /**
* 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 sign {@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 Long.toString(n, 16).toUpperCase()}
* </blockquote>
*
* @param i a {@code long} 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
*/
// radix 基数
public static String toString(long i, int radix) {
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
radix = 10;
if (radix == 10)
return toString(i);
char[] buf = new char[65];
int charPos = 64;
boolean negative = (i < 0); if (!negative) {
i = -i;
} while (i <= -radix) {
buf[charPos--] = Integer.digits[(int)(-(i % radix))];
i = i / radix;
}
buf[charPos] = Integer.digits[(int)(-i)]; if (negative) {
buf[--charPos] = '-';
} return new String(buf, charPos, (65 - 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(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.
*
* <p>The unsigned {@code long} value is the argument plus
* 2<sup>64</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
* Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(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 Long.toHexString(n).toUpperCase()}
* </blockquote>
*
* @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 hexadecimal
* (base 16).
* @see #parseUnsignedLong(String, int)
* @see #toUnsignedString(long, int)
* @since JDK 1.0.2
*/
public static String toHexString(long i) {
return toUnsignedString0(i, 4);
} /**
* Returns a string representation of the {@code long}
* argument as an unsigned integer in base 8.
*
* <p>The unsigned {@code long} value is the argument plus
* 2<sup>64</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
* Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(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 a {@code long} to be converted to a string.
* @return the string representation of the unsigned {@code long}
* value represented by the argument in octal (base 8).
* @see #parseUnsignedLong(String, int)
* @see #toUnsignedString(long, int)
* @since JDK 1.0.2
*/
public static String toOctalString(long i) {
return toUnsignedString0(i, 3);
} /**
* Returns a string representation of the {@code long}
* argument as an unsigned integer in base 2.
*
* <p>The unsigned {@code long} value is the argument plus
* 2<sup>64</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
* Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(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 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.
*
* <p>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.
*
* <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 {@code 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 long}.
* </ul>
*
* <p>Examples:
* <blockquote><pre>
* 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
* </pre></blockquote>
*
* @param s the {@code String} containing the
* {@code long} representation to be parsed.
* @param radix the radix to be used while parsing {@code s}.
* @return the {@code long} represented by the string argument in
* the specified radix.
* @throws NumberFormatException if the string does not contain a
* parsable {@code long}.
*/
public static long parseLong(String s, int radix)
throws NumberFormatException
{
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");
} long result = 0;
boolean negative = false;
int i = 0, len = s.length();
long limit = -Long.MAX_VALUE;
long multmin;
int digit; if (len > 0) {
char firstChar = s.charAt(0);
if (firstChar < '0') { // Possible leading "+" or "-"
if (firstChar == '-') {
negative = true;
limit = Long.MIN_VALUE;
} else if (firstChar != '+')
throw NumberFormatException.forInputString(s); if (len == 1) // Cannot have lone "+" or "-"
throw NumberFormatException.forInputString(s);
i++;
}
multmin = limit / radix;
while (i < len) {
// Accumulating negatively avoids surprises near MAX_VALUE
digit = Character.digit(s.charAt(i++),radix);
if (digit < 0) {
throw NumberFormatException.forInputString(s);
}
if (result < multmin) {
throw NumberFormatException.forInputString(s);
}
result *= radix;
if (result < limit + digit) {
throw NumberFormatException.forInputString(s);
}
result -= digit;
}
} else {
throw NumberFormatException.forInputString(s);
}
return negative ? result : -result;
} /**
* Parses the string argument as a signed decimal {@code long}.
* 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 {@code long} value is
* returned, exactly as if the argument and the radix {@code 10}
* were given as arguments to the {@link
* #parseLong(java.lang.String, int)} method.
*
* <p>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.
*
* <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 long}, 2<sup>64</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 unsigned {@code long} represented by the string
* argument in the specified radix.
* @throws NumberFormatException if the {@code String}
* does not contain a parsable {@code long}.
* @since 1.8
*/
public static long parseUnsignedLong(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 <= 12 || // Long.MAX_VALUE in Character.MAX_RADIX is 13 digits
(radix == 10 && len <= 18) ) { // Long.MAX_VALUE in base 10 is 19 digits
return parseLong(s, radix);
} // No need for range checks on len due to testing above.
long first = parseLong(s.substring(0, len - 1), radix);
int second = Character.digit(s.charAt(len - 1), radix);
if (second < 0) {
throw new NumberFormatException("Bad digit at end of " + s);
}
long result = first * radix + second;
if (compareUnsigned(result, first) < 0) {
/*
* The maximum unsigned value, (2^64)-1, takes at
* most one more digit to represent than the
* maximum signed value, (2^63)-1. Therefore,
* parsing (len - 1) digits will be appropriately
* in-range of the signed parsing. In other
* words, if parsing (len -1) digits overflows
* signed parsing, parsing len digits will
* certainly overflow unsigned parsing.
*
* The compareUnsigned check above catches
* situations where an unsigned overflow occurs
* incorporating the contribution of the final
* digit.
*/
throw new NumberFormatException(String.format("String value %s exceeds " +
"range of unsigned long.", s));
}
return result;
}
} else {
throw NumberFormatException.forInputString(s);
}
} /**
* Parses the string argument as an unsigned decimal {@code long}. The
* characters in the string must all be decimal digits, except
* that the first character may be an 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
* #parseUnsignedLong(java.lang.String, int)} method.
*
* @param s a {@code String} containing the unsigned {@code long}
* representation to be parsed
* @return the unsigned {@code long} value represented by the decimal string argument
* @throws NumberFormatException if the string does not contain a
* parsable unsigned integer.
* @since 1.8
*/
public static long parseUnsignedLong(String s) throws NumberFormatException {
return parseUnsignedLong(s, 10);
} /**
* Returns a {@code Long} 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
* {@code long} in the radix specified by the second
* argument, exactly as if the arguments were given to the {@link
* #parseLong(java.lang.String, int)} method. The result is a
* {@code Long} object that represents the {@code long}
* value specified by the string.
*
* <p>In other words, this method returns a {@code Long} object equal
* to the value of:
*
* <blockquote>
* {@code new Long(Long.parseLong(s, radix))}
* </blockquote>
*
* @param s the string to be parsed
* @param radix the radix to be used in interpreting {@code s}
* @return a {@code Long} object holding the value
* represented by the string argument in the specified
* radix.
* @throws NumberFormatException If the {@code String} does not
* contain a parsable {@code long}.
*/
public static Long valueOf(String s, int radix) throws NumberFormatException {
return Long.valueOf(parseLong(s, radix));
} /**
* Returns a {@code Long} object holding the value
* of the specified {@code String}. The argument is
* interpreted as representing a signed decimal {@code long},
* exactly as if the argument were given to the {@link
* #parseLong(java.lang.String)} method. The result is a
* {@code Long} object that represents the integer value
* specified by the string.
*
* <p>In other words, this method returns a {@code Long} object
* equal to the value of:
*
* <blockquote>
* {@code new Long(Long.parseLong(s))}
* </blockquote>
*
* @param s the string to be parsed.
* @return a {@code Long} object holding the value
* represented by the string argument.
* @throws NumberFormatException If the string cannot be parsed
* as a {@code long}.
*/
public static Long valueOf(String s) throws NumberFormatException
{
return Long.valueOf(parseLong(s, 10));
} private static class LongCache {
private LongCache(){} static final Long cache[] = new Long[-(-128) + 127 + 1]; static {
for(int i = 0; i < cache.length; i++)
cache[i] = new Long(i - 128);
}
} /**
* Returns a {@code Long} instance representing the specified
* {@code long} value.
* If a new {@code Long} instance is not required, this method
* should generally be used in preference to the constructor
* {@link #Long(long)}, as this method is likely to yield
* significantly better space and time performance by caching
* frequently requested values.
*
* Note that unlike the {@linkplain Integer#valueOf(int)
* corresponding method} in the {@code Integer} class, this method
* is <em>not</em> required to cache values within a particular
* range.
*
* @param l a long value.
* @return a {@code Long} instance representing {@code l}.
* @since 1.5
*/
public static Long valueOf(long l) {
final int offset = 128;
if (l >= -128 && l <= 127) { // will cache
return LongCache.cache[(int)l + offset];
}
return new Long(l);
} /**
* Decodes a {@code String} into a {@code Long}.
* 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
* 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:
*
* <blockquote>
* {@code (int)(this.longValue()^(this.longValue()>>>32))}
* </blockquote>
*
* @return a hash code value for this object.
*/
@Override
public int hashCode() {
return Long.hashCode(value);
} /**
* Returns a hash code for a {@code long} value; compatible with
* {@code Long.hashCode()}.
*
* @param value the value to hash
* @return a hash code value for a {@code long} value.
* @since 1.8
*/
public static int hashCode(long value) {
return (int)(value ^ (value >>> 32));
} /**
* Compares this object to the specified object. The result is
* {@code true} if and only if the argument is not
* {@code null} and is a {@code Long} object that
* contains the same {@code long} 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 Long) {
return value == ((Long)obj).longValue();
}
return false;
} /**
* Determines the {@code long} 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 a {@code
* long} value using the grammar supported by {@link Long#decode decode}
* and a {@code Long} 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 a {@code Long} object
* equal to the value of:
*
* <blockquote>
* {@code getLong(nm, null)}
* </blockquote>
*
* @param nm property name.
* @return the {@code Long} 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 Long getLong(String nm) {
return getLong(nm, null);
} /**
* Determines the {@code long} 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 a {@code
* long} value using the grammar supported by {@link Long#decode decode}
* and a {@code Long} object representing this value is returned.
*
* <p>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.
*
* <p>In other words, this method returns a {@code Long} object equal
* to the value of:
*
* <blockquote>
* {@code getLong(nm, new Long(val))}
* </blockquote>
*
* but in practice it may be implemented in a manner such as:
*
* <blockquote><pre>
* Long result = getLong(nm, null);
* return (result == null) ? new Long(val) : result;
* </pre></blockquote>
*
* to avoid the unnecessary allocation of a {@code Long} object when
* the default value is not needed.
*
* @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 java.lang.System#getProperty(java.lang.String)
* @see java.lang.System#getProperty(java.lang.String, java.lang.String)
*/
public static Long getLong(String nm, long val) {
Long result = Long.getLong(nm, null);
return (result == null) ? Long.valueOf(val) : result;
} /**
* Returns the {@code long} 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 a {@code long} value, as per the
* {@link Long#decode decode} method, and a {@code Long} 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 for 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>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.
*
* <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 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:
* <pre>
* Long.valueOf(x).compareTo(Long.valueOf(y))
* </pre>
*
* @param x the first {@code long} to compare
* @param y the second {@code long} 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(long x, long y) {
return (x < y) ? -1 : ((x == y) ? 0 : 1);
} /**
* Compares two {@code long} values numerically treating the values
* as unsigned.
*
* @param x the first {@code long} to compare
* @param y the second {@code long} 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(long x, long y) {
return compare(x + MIN_VALUE, y + MIN_VALUE);
} /**
* 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 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.
*
* <p>Note that this method is closely related to the logarithm base 2.
* For all positive {@code long} values x:
* <ul>
* <li>floor(log<sub>2</sub>(x)) = {@code 63 - numberOfLeadingZeros(x)}
* <li>ceil(log<sub>2</sub>(x)) = {@code 64 - 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 long} value, or 64 if the value
* is equal to zero.
* @since 1.5
*/
public static int numberOfLeadingZeros(long i) {
// HD, Figure 5-6
if (i == 0)
return 64;
int n = 1;
int x = (int)(i >>> 32);
if (x == 0) { n += 32; x = (int)i; }
if (x >>> 16 == 0) { n += 16; x <<= 16; }
if (x >>> 24 == 0) { n += 8; x <<= 8; }
if (x >>> 28 == 0) { n += 4; x <<= 4; }
if (x >>> 30 == 0) { n += 2; x <<= 2; }
n -= x >>> 31;
return n;
} /**
* Returns the number of zero bits following the lowest-order ("rightmost")
* 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.
*
* @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 long} value, or 64 if the value is equal
* to zero.
* @since 1.5
*/
public static int numberOfTrailingZeros(long i) {
// HD, Figure 5-14
int x, y;
if (i == 0) return 64;
int n = 63;
y = (int)i; if (y != 0) { n = n -32; x = y; } else x = (int)(i>>>32);
y = x <<16; if (y != 0) { n = n -16; x = y; }
y = x << 8; if (y != 0) { n = n - 8; x = y; }
y = x << 4; if (y != 0) { n = n - 4; x = y; }
y = x << 2; if (y != 0) { n = n - 2; x = y; }
return n - ((x << 1) >>> 31);
} /**
* Returns the number of one-bits in the two's complement binary
* representation of the specified {@code long} 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 long} value.
* @since 1.5
*/
public static int bitCount(long i) {
// HD, Figure 5-14
i = i - ((i >>> 1) & 0x5555555555555555L);
i = (i & 0x3333333333333333L) + ((i >>> 2) & 0x3333333333333333L);
i = (i + (i >>> 4)) & 0x0f0f0f0f0f0f0f0fL;
i = i + (i >>> 8);
i = i + (i >>> 16);
i = i + (i >>> 32);
return (int)i & 0x7f;
} /**
* Returns the value obtained by rotating the two's complement binary
* representation of the specified {@code long} 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 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.)
*
* <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 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;
}Long Source
LongCache的常量池 [-128,127] 有效值。
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