- 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。
1 // final修饰符 2 public final class Long extends Number implements Comparable<Long> { 3 /** 4 * A constant holding the minimum value a {@code long} can 5 * have, -2<sup>63</sup>. 6 */ 7 // 最小值-负值 8 @Native public static final long MIN_VALUE = 0x8000000000000000L; 9 10 /** 11 * A constant holding the maximum value a {@code long} can 12 * have, 2<sup>63</sup>-1. 13 */ 14 // 最大值-有符号 15 @Native public static final long MAX_VALUE = 0x7fffffffffffffffL; 16 17 /** 18 * The {@code Class} instance representing the primitive type 19 * {@code long}. 20 * 21 * @since JDK1.1 22 */ 23 @SuppressWarnings("unchecked") 24 // class 25 public static final Class<Long> TYPE = (Class<Long>) Class.getPrimitiveClass("long"); 26 27 /** 28 * Returns a string representation of the first argument in the 29 * radix specified by the second argument. 30 * 31 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 32 * or larger than {@code Character.MAX_RADIX}, then the radix 33 * {@code 10} is used instead. 34 * 35 * <p>If the first argument is negative, the first element of the 36 * result is the ASCII minus sign {@code ‘-‘} 37 * ({@code ‘\u005Cu002d‘}). If the first argument is not 38 * negative, no sign character appears in the result. 39 * 40 * <p>The remaining characters of the result represent the magnitude 41 * of the first argument. If the magnitude is zero, it is 42 * represented by a single zero character {@code ‘0‘} 43 * ({@code ‘\u005Cu0030‘}); otherwise, the first character of 44 * the representation of the magnitude will not be the zero 45 * character. The following ASCII characters are used as digits: 46 * 47 * <blockquote> 48 * {@code 0123456789abcdefghijklmnopqrstuvwxyz} 49 * </blockquote> 50 * 51 * These are {@code ‘\u005Cu0030‘} through 52 * {@code ‘\u005Cu0039‘} and {@code ‘\u005Cu0061‘} through 53 * {@code ‘\u005Cu007a‘}. If {@code radix} is 54 * <var>N</var>, then the first <var>N</var> of these characters 55 * are used as radix-<var>N</var> digits in the order shown. Thus, 56 * the digits for hexadecimal (radix 16) are 57 * {@code 0123456789abcdef}. If uppercase letters are 58 * desired, the {@link java.lang.String#toUpperCase()} method may 59 * be called on the result: 60 * 61 * <blockquote> 62 * {@code Long.toString(n, 16).toUpperCase()} 63 * </blockquote> 64 * 65 * @param i a {@code long} to be converted to a string. 66 * @param radix the radix to use in the string representation. 67 * @return a string representation of the argument in the specified radix. 68 * @see java.lang.Character#MAX_RADIX 69 * @see java.lang.Character#MIN_RADIX 70 */ 71 // radix 基数 72 public static String toString(long i, int radix) { 73 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) 74 radix = 10; 75 if (radix == 10) 76 return toString(i); 77 char[] buf = new char[65]; 78 int charPos = 64; 79 boolean negative = (i < 0); 80 81 if (!negative) { 82 i = -i; 83 } 84 85 while (i <= -radix) { 86 buf[charPos--] = Integer.digits[(int)(-(i % radix))]; 87 i = i / radix; 88 } 89 buf[charPos] = Integer.digits[(int)(-i)]; 90 91 if (negative) { 92 buf[--charPos] = ‘-‘; 93 } 94 95 return new String(buf, charPos, (65 - charPos)); 96 } 97 98 /** 99 * Returns a string representation of the first argument as an 100 * unsigned integer value in the radix specified by the second 101 * argument. 102 * 103 * <p>If the radix is smaller than {@code Character.MIN_RADIX} 104 * or larger than {@code Character.MAX_RADIX}, then the radix 105 * {@code 10} is used instead. 106 * 107 * <p>Note that since the first argument is treated as an unsigned 108 * value, no leading sign character is printed. 109 * 110 * <p>If the magnitude is zero, it is represented by a single zero 111 * character {@code ‘0‘} ({@code ‘\u005Cu0030‘}); otherwise, 112 * the first character of the representation of the magnitude will 113 * not be the zero character. 114 * 115 * <p>The behavior of radixes and the characters used as digits 116 * are the same as {@link #toString(long, int) toString}. 117 * 118 * @param i an integer to be converted to an unsigned string. 119 * @param radix the radix to use in the string representation. 120 * @return an unsigned string representation of the argument in the specified radix. 121 * @see #toString(long, int) 122 * @since 1.8 123 */ 124 public static String toUnsignedString(long i, int radix) { 125 if (i >= 0) 126 return toString(i, radix); 127 else { 128 switch (radix) { 129 case 2: 130 return toBinaryString(i); 131 132 case 4: 133 return toUnsignedString0(i, 2); 134 135 case 8: 136 return toOctalString(i); 137 138 case 10: 139 /* 140 * We can get the effect of an unsigned division by 10 141 * on a long value by first shifting right, yielding a 142 * positive value, and then dividing by 5. This 143 * allows the last digit and preceding digits to be 144 * isolated more quickly than by an initial conversion 145 * to BigInteger. 146 */ 147 long quot = (i >>> 1) / 5; 148 long rem = i - quot * 10; 149 return toString(quot) + rem; 150 151 case 16: 152 return toHexString(i); 153 154 case 32: 155 return toUnsignedString0(i, 5); 156 157 default: 158 return toUnsignedBigInteger(i).toString(radix); 159 } 160 } 161 } 162 163 /** 164 * Return a BigInteger equal to the unsigned value of the 165 * argument. 166 */ 167 private static BigInteger toUnsignedBigInteger(long i) { 168 if (i >= 0L) 169 return BigInteger.valueOf(i); 170 else { 171 int upper = (int) (i >>> 32); 172 int lower = (int) i; 173 174 // return (upper << 32) + lower 175 return (BigInteger.valueOf(Integer.toUnsignedLong(upper))).shiftLeft(32). 176 add(BigInteger.valueOf(Integer.toUnsignedLong(lower))); 177 } 178 } 179 180 /** 181 * Returns a string representation of the {@code long} 182 * argument as an unsigned integer in base 16. 183 * 184 * <p>The unsigned {@code long} value is the argument plus 185 * 2<sup>64</sup> if the argument is negative; otherwise, it is 186 * equal to the argument. This value is converted to a string of 187 * ASCII digits in hexadecimal (base 16) with no extra 188 * leading {@code 0}s. 189 * 190 * <p>The value of the argument can be recovered from the returned 191 * string {@code s} by calling {@link 192 * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, 193 * 16)}. 194 * 195 * <p>If the unsigned magnitude is zero, it is represented by a 196 * single zero character {@code ‘0‘} ({@code ‘\u005Cu0030‘}); 197 * otherwise, the first character of the representation of the 198 * unsigned magnitude will not be the zero character. The 199 * following characters are used as hexadecimal digits: 200 * 201 * <blockquote> 202 * {@code 0123456789abcdef} 203 * </blockquote> 204 * 205 * These are the characters {@code ‘\u005Cu0030‘} through 206 * {@code ‘\u005Cu0039‘} and {@code ‘\u005Cu0061‘} through 207 * {@code ‘\u005Cu0066‘}. If uppercase letters are desired, 208 * the {@link java.lang.String#toUpperCase()} method may be called 209 * on the result: 210 * 211 * <blockquote> 212 * {@code Long.toHexString(n).toUpperCase()} 213 * </blockquote> 214 * 215 * @param i a {@code long} to be converted to a string. 216 * @return the string representation of the unsigned {@code long} 217 * value represented by the argument in hexadecimal 218 * (base 16). 219 * @see #parseUnsignedLong(String, int) 220 * @see #toUnsignedString(long, int) 221 * @since JDK 1.0.2 222 */ 223 public static String toHexString(long i) { 224 return toUnsignedString0(i, 4); 225 } 226 227 /** 228 * Returns a string representation of the {@code long} 229 * argument as an unsigned integer in base 8. 230 * 231 * <p>The unsigned {@code long} value is the argument plus 232 * 2<sup>64</sup> if the argument is negative; otherwise, it is 233 * equal to the argument. This value is converted to a string of 234 * ASCII digits in octal (base 8) with no extra leading 235 * {@code 0}s. 236 * 237 * <p>The value of the argument can be recovered from the returned 238 * string {@code s} by calling {@link 239 * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, 240 * 8)}. 241 * 242 * <p>If the unsigned magnitude is zero, it is represented by a 243 * single zero character {@code ‘0‘} ({@code ‘\u005Cu0030‘}); 244 * otherwise, the first character of the representation of the 245 * unsigned magnitude will not be the zero character. The 246 * following characters are used as octal digits: 247 * 248 * <blockquote> 249 * {@code 01234567} 250 * </blockquote> 251 * 252 * These are the characters {@code ‘\u005Cu0030‘} through 253 * {@code ‘\u005Cu0037‘}. 254 * 255 * @param i a {@code long} to be converted to a string. 256 * @return the string representation of the unsigned {@code long} 257 * value represented by the argument in octal (base 8). 258 * @see #parseUnsignedLong(String, int) 259 * @see #toUnsignedString(long, int) 260 * @since JDK 1.0.2 261 */ 262 public static String toOctalString(long i) { 263 return toUnsignedString0(i, 3); 264 } 265 266 /** 267 * Returns a string representation of the {@code long} 268 * argument as an unsigned integer in base 2. 269 * 270 * <p>The unsigned {@code long} value is the argument plus 271 * 2<sup>64</sup> if the argument is negative; otherwise, it is 272 * equal to the argument. This value is converted to a string of 273 * ASCII digits in binary (base 2) with no extra leading 274 * {@code 0}s. 275 * 276 * <p>The value of the argument can be recovered from the returned 277 * string {@code s} by calling {@link 278 * Long#parseUnsignedLong(String, int) Long.parseUnsignedLong(s, 279 * 2)}. 280 * 281 * <p>If the unsigned magnitude is zero, it is represented by a 282 * single zero character {@code ‘0‘} ({@code ‘\u005Cu0030‘}); 283 * otherwise, the first character of the representation of the 284 * unsigned magnitude will not be the zero character. The 285 * characters {@code ‘0‘} ({@code ‘\u005Cu0030‘}) and {@code 286 * ‘1‘} ({@code ‘\u005Cu0031‘}) are used as binary digits. 287 * 288 * @param i a {@code long} to be converted to a string. 289 * @return the string representation of the unsigned {@code long} 290 * value represented by the argument in binary (base 2). 291 * @see #parseUnsignedLong(String, int) 292 * @see #toUnsignedString(long, int) 293 * @since JDK 1.0.2 294 */ 295 public static String toBinaryString(long i) { 296 return toUnsignedString0(i, 1); 297 } 298 299 /** 300 * Format a long (treated as unsigned) into a String. 301 * @param val the value to format 302 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) 303 */ 304 static String toUnsignedString0(long val, int shift) { 305 // assert shift > 0 && shift <=5 : "Illegal shift value"; 306 int mag = Long.SIZE - Long.numberOfLeadingZeros(val); 307 int chars = Math.max(((mag + (shift - 1)) / shift), 1); 308 char[] buf = new char[chars]; 309 310 formatUnsignedLong(val, shift, buf, 0, chars); 311 return new String(buf, true); 312 } 313 314 /** 315 * Format a long (treated as unsigned) into a character buffer. 316 * @param val the unsigned long to format 317 * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary) 318 * @param buf the character buffer to write to 319 * @param offset the offset in the destination buffer to start at 320 * @param len the number of characters to write 321 * @return the lowest character location used 322 */ 323 static int formatUnsignedLong(long val, int shift, char[] buf, int offset, int len) { 324 int charPos = len; 325 int radix = 1 << shift; 326 int mask = radix - 1; 327 do { 328 buf[offset + --charPos] = Integer.digits[((int) val) & mask]; 329 val >>>= shift; 330 } while (val != 0 && charPos > 0); 331 332 return charPos; 333 } 334 335 /** 336 * Returns a {@code String} object representing the specified 337 * {@code long}. The argument is converted to signed decimal 338 * representation and returned as a string, exactly as if the 339 * argument and the radix 10 were given as arguments to the {@link 340 * #toString(long, int)} method. 341 * 342 * @param i a {@code long} to be converted. 343 * @return a string representation of the argument in base 10. 344 */ 345 public static String toString(long i) { 346 if (i == Long.MIN_VALUE) 347 return "-9223372036854775808"; 348 int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i); 349 char[] buf = new char[size]; 350 getChars(i, size, buf); 351 return new String(buf, true); 352 } 353 354 /** 355 * Returns a string representation of the argument as an unsigned 356 * decimal value. 357 * 358 * The argument is converted to unsigned decimal representation 359 * and returned as a string exactly as if the argument and radix 360 * 10 were given as arguments to the {@link #toUnsignedString(long, 361 * int)} method. 362 * 363 * @param i an integer to be converted to an unsigned string. 364 * @return an unsigned string representation of the argument. 365 * @see #toUnsignedString(long, int) 366 * @since 1.8 367 */ 368 public static String toUnsignedString(long i) { 369 return toUnsignedString(i, 10); 370 } 371 372 /** 373 * Places characters representing the integer i into the 374 * character array buf. The characters are placed into 375 * the buffer backwards starting with the least significant 376 * digit at the specified index (exclusive), and working 377 * backwards from there. 378 * 379 * Will fail if i == Long.MIN_VALUE 380 */ 381 static void getChars(long i, int index, char[] buf) { 382 long q; 383 int r; 384 int charPos = index; 385 char sign = 0; 386 387 if (i < 0) { 388 sign = ‘-‘; 389 i = -i; 390 } 391 392 // Get 2 digits/iteration using longs until quotient fits into an int 393 while (i > Integer.MAX_VALUE) { 394 q = i / 100; 395 // really: r = i - (q * 100); 396 r = (int)(i - ((q << 6) + (q << 5) + (q << 2))); 397 i = q; 398 buf[--charPos] = Integer.DigitOnes[r]; 399 buf[--charPos] = Integer.DigitTens[r]; 400 } 401 402 // Get 2 digits/iteration using ints 403 int q2; 404 int i2 = (int)i; 405 while (i2 >= 65536) { 406 q2 = i2 / 100; 407 // really: r = i2 - (q * 100); 408 r = i2 - ((q2 << 6) + (q2 << 5) + (q2 << 2)); 409 i2 = q2; 410 buf[--charPos] = Integer.DigitOnes[r]; 411 buf[--charPos] = Integer.DigitTens[r]; 412 } 413 414 // Fall thru to fast mode for smaller numbers 415 // assert(i2 <= 65536, i2); 416 for (;;) { 417 q2 = (i2 * 52429) >>> (16+3); 418 r = i2 - ((q2 << 3) + (q2 << 1)); // r = i2-(q2*10) ... 419 buf[--charPos] = Integer.digits[r]; 420 i2 = q2; 421 if (i2 == 0) break; 422 } 423 if (sign != 0) { 424 buf[--charPos] = sign; 425 } 426 } 427 428 // Requires positive x 429 static int stringSize(long x) { 430 long p = 10; 431 for (int i=1; i<19; i++) { 432 if (x < p) 433 return i; 434 p = 10*p; 435 } 436 return 19; 437 } 438 439 /** 440 * Parses the string argument as a signed {@code long} in the 441 * radix specified by the second argument. The characters in the 442 * string must all be digits of the specified radix (as determined 443 * by whether {@link java.lang.Character#digit(char, int)} returns 444 * a nonnegative value), except that the first character may be an 445 * ASCII minus sign {@code ‘-‘} ({@code ‘\u005Cu002D‘}) to 446 * indicate a negative value or an ASCII plus sign {@code ‘+‘} 447 * ({@code ‘\u005Cu002B‘}) to indicate a positive value. The 448 * resulting {@code long} value is returned. 449 * 450 * <p>Note that neither the character {@code L} 451 * ({@code ‘\u005Cu004C‘}) nor {@code l} 452 * ({@code ‘\u005Cu006C‘}) is permitted to appear at the end 453 * of the string as a type indicator, as would be permitted in 454 * Java programming language source code - except that either 455 * {@code L} or {@code l} may appear as a digit for a 456 * radix greater than or equal to 22. 457 * 458 * <p>An exception of type {@code NumberFormatException} is 459 * thrown if any of the following situations occurs: 460 * <ul> 461 * 462 * <li>The first argument is {@code null} or is a string of 463 * length zero. 464 * 465 * <li>The {@code radix} is either smaller than {@link 466 * java.lang.Character#MIN_RADIX} or larger than {@link 467 * java.lang.Character#MAX_RADIX}. 468 * 469 * <li>Any character of the string is not a digit of the specified 470 * radix, except that the first character may be a minus sign 471 * {@code ‘-‘} ({@code ‘\u005Cu002d‘}) or plus sign {@code 472 * ‘+‘} ({@code ‘\u005Cu002B‘}) provided that the string is 473 * longer than length 1. 474 * 475 * <li>The value represented by the string is not a value of type 476 * {@code long}. 477 * </ul> 478 * 479 * <p>Examples: 480 * <blockquote><pre> 481 * parseLong("0", 10) returns 0L 482 * parseLong("473", 10) returns 473L 483 * parseLong("+42", 10) returns 42L 484 * parseLong("-0", 10) returns 0L 485 * parseLong("-FF", 16) returns -255L 486 * parseLong("1100110", 2) returns 102L 487 * parseLong("99", 8) throws a NumberFormatException 488 * parseLong("Hazelnut", 10) throws a NumberFormatException 489 * parseLong("Hazelnut", 36) returns 1356099454469L 490 * </pre></blockquote> 491 * 492 * @param s the {@code String} containing the 493 * {@code long} representation to be parsed. 494 * @param radix the radix to be used while parsing {@code s}. 495 * @return the {@code long} represented by the string argument in 496 * the specified radix. 497 * @throws NumberFormatException if the string does not contain a 498 * parsable {@code long}. 499 */ 500 public static long parseLong(String s, int radix) 501 throws NumberFormatException 502 { 503 if (s == null) { 504 throw new NumberFormatException("null"); 505 } 506 507 if (radix < Character.MIN_RADIX) { 508 throw new NumberFormatException("radix " + radix + 509 " less than Character.MIN_RADIX"); 510 } 511 if (radix > Character.MAX_RADIX) { 512 throw new NumberFormatException("radix " + radix + 513 " greater than Character.MAX_RADIX"); 514 } 515 516 long result = 0; 517 boolean negative = false; 518 int i = 0, len = s.length(); 519 long limit = -Long.MAX_VALUE; 520 long multmin; 521 int digit; 522 523 if (len > 0) { 524 char firstChar = s.charAt(0); 525 if (firstChar < ‘0‘) { // Possible leading "+" or "-" 526 if (firstChar == ‘-‘) { 527 negative = true; 528 limit = Long.MIN_VALUE; 529 } else if (firstChar != ‘+‘) 530 throw NumberFormatException.forInputString(s); 531 532 if (len == 1) // Cannot have lone "+" or "-" 533 throw NumberFormatException.forInputString(s); 534 i++; 535 } 536 multmin = limit / radix; 537 while (i < len) { 538 // Accumulating negatively avoids surprises near MAX_VALUE 539 digit = Character.digit(s.charAt(i++),radix); 540 if (digit < 0) { 541 throw NumberFormatException.forInputString(s); 542 } 543 if (result < multmin) { 544 throw NumberFormatException.forInputString(s); 545 } 546 result *= radix; 547 if (result < limit + digit) { 548 throw NumberFormatException.forInputString(s); 549 } 550 result -= digit; 551 } 552 } else { 553 throw NumberFormatException.forInputString(s); 554 } 555 return negative ? result : -result; 556 } 557 558 /** 559 * Parses the string argument as a signed decimal {@code long}. 560 * The characters in the string must all be decimal digits, except 561 * that the first character may be an ASCII minus sign {@code ‘-‘} 562 * ({@code \u005Cu002D‘}) to indicate a negative value or an 563 * ASCII plus sign {@code ‘+‘} ({@code ‘\u005Cu002B‘}) to 564 * indicate a positive value. The resulting {@code long} value is 565 * returned, exactly as if the argument and the radix {@code 10} 566 * were given as arguments to the {@link 567 * #parseLong(java.lang.String, int)} method. 568 * 569 * <p>Note that neither the character {@code L} 570 * ({@code ‘\u005Cu004C‘}) nor {@code l} 571 * ({@code ‘\u005Cu006C‘}) is permitted to appear at the end 572 * of the string as a type indicator, as would be permitted in 573 * Java programming language source code. 574 * 575 * @param s a {@code String} containing the {@code long} 576 * representation to be parsed 577 * @return the {@code long} represented by the argument in 578 * decimal. 579 * @throws NumberFormatException if the string does not contain a 580 * parsable {@code long}. 581 */ 582 public static long parseLong(String s) throws NumberFormatException { 583 return parseLong(s, 10); 584 } 585 586 /** 587 * Parses the string argument as an unsigned {@code long} in the 588 * radix specified by the second argument. An unsigned integer 589 * maps the values usually associated with negative numbers to 590 * positive numbers larger than {@code MAX_VALUE}. 591 * 592 * The characters in the string must all be digits of the 593 * specified radix (as determined by whether {@link 594 * java.lang.Character#digit(char, int)} returns a nonnegative 595 * value), except that the first character may be an ASCII plus 596 * sign {@code ‘+‘} ({@code ‘\u005Cu002B‘}). The resulting 597 * integer value is returned. 598 * 599 * <p>An exception of type {@code NumberFormatException} is 600 * thrown if any of the following situations occurs: 601 * <ul> 602 * <li>The first argument is {@code null} or is a string of 603 * length zero. 604 * 605 * <li>The radix is either smaller than 606 * {@link java.lang.Character#MIN_RADIX} or 607 * larger than {@link java.lang.Character#MAX_RADIX}. 608 * 609 * <li>Any character of the string is not a digit of the specified 610 * radix, except that the first character may be a plus sign 611 * {@code ‘+‘} ({@code ‘\u005Cu002B‘}) provided that the 612 * string is longer than length 1. 613 * 614 * <li>The value represented by the string is larger than the 615 * largest unsigned {@code long}, 2<sup>64</sup>-1. 616 * 617 * </ul> 618 * 619 * 620 * @param s the {@code String} containing the unsigned integer 621 * representation to be parsed 622 * @param radix the radix to be used while parsing {@code s}. 623 * @return the unsigned {@code long} represented by the string 624 * argument in the specified radix. 625 * @throws NumberFormatException if the {@code String} 626 * does not contain a parsable {@code long}. 627 * @since 1.8 628 */ 629 public static long parseUnsignedLong(String s, int radix) 630 throws NumberFormatException { 631 if (s == null) { 632 throw new NumberFormatException("null"); 633 } 634 635 int len = s.length(); 636 if (len > 0) { 637 char firstChar = s.charAt(0); 638 if (firstChar == ‘-‘) { 639 throw new 640 NumberFormatException(String.format("Illegal leading minus sign " + 641 "on unsigned string %s.", s)); 642 } else { 643 if (len <= 12 || // Long.MAX_VALUE in Character.MAX_RADIX is 13 digits 644 (radix == 10 && len <= 18) ) { // Long.MAX_VALUE in base 10 is 19 digits 645 return parseLong(s, radix); 646 } 647 648 // No need for range checks on len due to testing above. 649 long first = parseLong(s.substring(0, len - 1), radix); 650 int second = Character.digit(s.charAt(len - 1), radix); 651 if (second < 0) { 652 throw new NumberFormatException("Bad digit at end of " + s); 653 } 654 long result = first * radix + second; 655 if (compareUnsigned(result, first) < 0) { 656 /* 657 * The maximum unsigned value, (2^64)-1, takes at 658 * most one more digit to represent than the 659 * maximum signed value, (2^63)-1. Therefore, 660 * parsing (len - 1) digits will be appropriately 661 * in-range of the signed parsing. In other 662 * words, if parsing (len -1) digits overflows 663 * signed parsing, parsing len digits will 664 * certainly overflow unsigned parsing. 665 * 666 * The compareUnsigned check above catches 667 * situations where an unsigned overflow occurs 668 * incorporating the contribution of the final 669 * digit. 670 */ 671 throw new NumberFormatException(String.format("String value %s exceeds " + 672 "range of unsigned long.", s)); 673 } 674 return result; 675 } 676 } else { 677 throw NumberFormatException.forInputString(s); 678 } 679 } 680 681 /** 682 * Parses the string argument as an unsigned decimal {@code long}. The 683 * characters in the string must all be decimal digits, except 684 * that the first character may be an an ASCII plus sign {@code 685 * ‘+‘} ({@code ‘\u005Cu002B‘}). The resulting integer value 686 * is returned, exactly as if the argument and the radix 10 were 687 * given as arguments to the {@link 688 * #parseUnsignedLong(java.lang.String, int)} method. 689 * 690 * @param s a {@code String} containing the unsigned {@code long} 691 * representation to be parsed 692 * @return the unsigned {@code long} value represented by the decimal string argument 693 * @throws NumberFormatException if the string does not contain a 694 * parsable unsigned integer. 695 * @since 1.8 696 */ 697 public static long parseUnsignedLong(String s) throws NumberFormatException { 698 return parseUnsignedLong(s, 10); 699 } 700 701 /** 702 * Returns a {@code Long} object holding the value 703 * extracted from the specified {@code String} when parsed 704 * with the radix given by the second argument. The first 705 * argument is interpreted as representing a signed 706 * {@code long} in the radix specified by the second 707 * argument, exactly as if the arguments were given to the {@link 708 * #parseLong(java.lang.String, int)} method. The result is a 709 * {@code Long} object that represents the {@code long} 710 * value specified by the string. 711 * 712 * <p>In other words, this method returns a {@code Long} object equal 713 * to the value of: 714 * 715 * <blockquote> 716 * {@code new Long(Long.parseLong(s, radix))} 717 * </blockquote> 718 * 719 * @param s the string to be parsed 720 * @param radix the radix to be used in interpreting {@code s} 721 * @return a {@code Long} object holding the value 722 * represented by the string argument in the specified 723 * radix. 724 * @throws NumberFormatException If the {@code String} does not 725 * contain a parsable {@code long}. 726 */ 727 public static Long valueOf(String s, int radix) throws NumberFormatException { 728 return Long.valueOf(parseLong(s, radix)); 729 } 730 731 /** 732 * Returns a {@code Long} object holding the value 733 * of the specified {@code String}. The argument is 734 * interpreted as representing a signed decimal {@code long}, 735 * exactly as if the argument were given to the {@link 736 * #parseLong(java.lang.String)} method. The result is a 737 * {@code Long} object that represents the integer value 738 * specified by the string. 739 * 740 * <p>In other words, this method returns a {@code Long} object 741 * equal to the value of: 742 * 743 * <blockquote> 744 * {@code new Long(Long.parseLong(s))} 745 * </blockquote> 746 * 747 * @param s the string to be parsed. 748 * @return a {@code Long} object holding the value 749 * represented by the string argument. 750 * @throws NumberFormatException If the string cannot be parsed 751 * as a {@code long}. 752 */ 753 public static Long valueOf(String s) throws NumberFormatException 754 { 755 return Long.valueOf(parseLong(s, 10)); 756 } 757 758 private static class LongCache { 759 private LongCache(){} 760 761 static final Long cache[] = new Long[-(-128) + 127 + 1]; 762 763 static { 764 for(int i = 0; i < cache.length; i++) 765 cache[i] = new Long(i - 128); 766 } 767 } 768 769 /** 770 * Returns a {@code Long} instance representing the specified 771 * {@code long} value. 772 * If a new {@code Long} instance is not required, this method 773 * should generally be used in preference to the constructor 774 * {@link #Long(long)}, as this method is likely to yield 775 * significantly better space and time performance by caching 776 * frequently requested values. 777 * 778 * Note that unlike the {@linkplain Integer#valueOf(int) 779 * corresponding method} in the {@code Integer} class, this method 780 * is <em>not</em> required to cache values within a particular 781 * range. 782 * 783 * @param l a long value. 784 * @return a {@code Long} instance representing {@code l}. 785 * @since 1.5 786 */ 787 public static Long valueOf(long l) { 788 final int offset = 128; 789 if (l >= -128 && l <= 127) { // will cache 790 return LongCache.cache[(int)l + offset]; 791 } 792 return new Long(l); 793 } 794 795 /** 796 * Decodes a {@code String} into a {@code Long}. 797 * Accepts decimal, hexadecimal, and octal numbers given by the 798 * following grammar: 799 * 800 * <blockquote> 801 * <dl> 802 * <dt><i>DecodableString:</i> 803 * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i> 804 * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i> 805 * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i> 806 * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i> 807 * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i> 808 * 809 * <dt><i>Sign:</i> 810 * <dd>{@code -} 811 * <dd>{@code +} 812 * </dl> 813 * </blockquote> 814 * 815 * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i> 816 * are as defined in section 3.10.1 of 817 * <cite>The Java™ Language Specification</cite>, 818 * except that underscores are not accepted between digits. 819 * 820 * <p>The sequence of characters following an optional 821 * sign and/or radix specifier ("{@code 0x}", "{@code 0X}", 822 * "{@code #}", or leading zero) is parsed as by the {@code 823 * Long.parseLong} method with the indicated radix (10, 16, or 8). 824 * This sequence of characters must represent a positive value or 825 * a {@link NumberFormatException} will be thrown. The result is 826 * negated if first character of the specified {@code String} is 827 * the minus sign. No whitespace characters are permitted in the 828 * {@code String}. 829 * 830 * @param nm the {@code String} to decode. 831 * @return a {@code Long} object holding the {@code long} 832 * value represented by {@code nm} 833 * @throws NumberFormatException if the {@code String} does not 834 * contain a parsable {@code long}. 835 * @see java.lang.Long#parseLong(String, int) 836 * @since 1.2 837 */ 838 public static Long decode(String nm) throws NumberFormatException { 839 int radix = 10; 840 int index = 0; 841 boolean negative = false; 842 Long result; 843 844 if (nm.length() == 0) 845 throw new NumberFormatException("Zero length string"); 846 char firstChar = nm.charAt(0); 847 // Handle sign, if present 848 if (firstChar == ‘-‘) { 849 negative = true; 850 index++; 851 } else if (firstChar == ‘+‘) 852 index++; 853 854 // Handle radix specifier, if present 855 if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) { 856 index += 2; 857 radix = 16; 858 } 859 else if (nm.startsWith("#", index)) { 860 index ++; 861 radix = 16; 862 } 863 else if (nm.startsWith("0", index) && nm.length() > 1 + index) { 864 index ++; 865 radix = 8; 866 } 867 868 if (nm.startsWith("-", index) || nm.startsWith("+", index)) 869 throw new NumberFormatException("Sign character in wrong position"); 870 871 try { 872 result = Long.valueOf(nm.substring(index), radix); 873 result = negative ? Long.valueOf(-result.longValue()) : result; 874 } catch (NumberFormatException e) { 875 // If number is Long.MIN_VALUE, we‘ll end up here. The next line 876 // handles this case, and causes any genuine format error to be 877 // rethrown. 878 String constant = negative ? ("-" + nm.substring(index)) 879 : nm.substring(index); 880 result = Long.valueOf(constant, radix); 881 } 882 return result; 883 } 884 885 /** 886 * The value of the {@code Long}. 887 * 888 * @serial 889 */ 890 private final long value; 891 892 /** 893 * Constructs a newly allocated {@code Long} object that 894 * represents the specified {@code long} argument. 895 * 896 * @param value the value to be represented by the 897 * {@code Long} object. 898 */ 899 public Long(long value) { 900 this.value = value; 901 } 902 903 /** 904 * Constructs a newly allocated {@code Long} object that 905 * represents the {@code long} value indicated by the 906 * {@code String} parameter. The string is converted to a 907 * {@code long} value in exactly the manner used by the 908 * {@code parseLong} method for radix 10. 909 * 910 * @param s the {@code String} to be converted to a 911 * {@code Long}. 912 * @throws NumberFormatException if the {@code String} does not 913 * contain a parsable {@code long}. 914 * @see java.lang.Long#parseLong(java.lang.String, int) 915 */ 916 public Long(String s) throws NumberFormatException { 917 this.value = parseLong(s, 10); 918 } 919 920 /** 921 * Returns the value of this {@code Long} as a {@code byte} after 922 * a narrowing primitive conversion. 923 * @jls 5.1.3 Narrowing Primitive Conversions 924 */ 925 public byte byteValue() { 926 return (byte)value; 927 } 928 929 /** 930 * Returns the value of this {@code Long} as a {@code short} after 931 * a narrowing primitive conversion. 932 * @jls 5.1.3 Narrowing Primitive Conversions 933 */ 934 public short shortValue() { 935 return (short)value; 936 } 937 938 /** 939 * Returns the value of this {@code Long} as an {@code int} after 940 * a narrowing primitive conversion. 941 * @jls 5.1.3 Narrowing Primitive Conversions 942 */ 943 public int intValue() { 944 return (int)value; 945 } 946 947 /** 948 * Returns the value of this {@code Long} as a 949 * {@code long} value. 950 */ 951 public long longValue() { 952 return value; 953 } 954 955 /** 956 * Returns the value of this {@code Long} as a {@code float} after 957 * a widening primitive conversion. 958 * @jls 5.1.2 Widening Primitive Conversions 959 */ 960 public float floatValue() { 961 return (float)value; 962 } 963 964 /** 965 * Returns the value of this {@code Long} as a {@code double} 966 * after a widening primitive conversion. 967 * @jls 5.1.2 Widening Primitive Conversions 968 */ 969 public double doubleValue() { 970 return (double)value; 971 } 972 973 /** 974 * Returns a {@code String} object representing this 975 * {@code Long}‘s value. The value is converted to signed 976 * decimal representation and returned as a string, exactly as if 977 * the {@code long} value were given as an argument to the 978 * {@link java.lang.Long#toString(long)} method. 979 * 980 * @return a string representation of the value of this object in 981 * base 10. 982 */ 983 public String toString() { 984 return toString(value); 985 } 986 987 /** 988 * Returns a hash code for this {@code Long}. The result is 989 * the exclusive OR of the two halves of the primitive 990 * {@code long} value held by this {@code Long} 991 * object. That is, the hashcode is the value of the expression: 992 * 993 * <blockquote> 994 * {@code (int)(this.longValue()^(this.longValue()>>>32))} 995 * </blockquote> 996 * 997 * @return a hash code value for this object. 998 */ 999 @Override 1000 public int hashCode() { 1001 return Long.hashCode(value); 1002 } 1003 1004 /** 1005 * Returns a hash code for a {@code long} value; compatible with 1006 * {@code Long.hashCode()}. 1007 * 1008 * @param value the value to hash 1009 * @return a hash code value for a {@code long} value. 1010 * @since 1.8 1011 */ 1012 public static int hashCode(long value) { 1013 return (int)(value ^ (value >>> 32)); 1014 } 1015 1016 /** 1017 * Compares this object to the specified object. The result is 1018 * {@code true} if and only if the argument is not 1019 * {@code null} and is a {@code Long} object that 1020 * contains the same {@code long} value as this object. 1021 * 1022 * @param obj the object to compare with. 1023 * @return {@code true} if the objects are the same; 1024 * {@code false} otherwise. 1025 */ 1026 public boolean equals(Object obj) { 1027 if (obj instanceof Long) { 1028 return value == ((Long)obj).longValue(); 1029 } 1030 return false; 1031 } 1032 1033 /** 1034 * Determines the {@code long} value of the system property 1035 * with the specified name. 1036 * 1037 * <p>The first argument is treated as the name of a system 1038 * property. System properties are accessible through the {@link 1039 * java.lang.System#getProperty(java.lang.String)} method. The 1040 * string value of this property is then interpreted as a {@code 1041 * long} value using the grammar supported by {@link Long#decode decode} 1042 * and a {@code Long} object representing this value is returned. 1043 * 1044 * <p>If there is no property with the specified name, if the 1045 * specified name is empty or {@code null}, or if the property 1046 * does not have the correct numeric format, then {@code null} is 1047 * returned. 1048 * 1049 * <p>In other words, this method returns a {@code Long} object 1050 * equal to the value of: 1051 * 1052 * <blockquote> 1053 * {@code getLong(nm, null)} 1054 * </blockquote> 1055 * 1056 * @param nm property name. 1057 * @return the {@code Long} value of the property. 1058 * @throws SecurityException for the same reasons as 1059 * {@link System#getProperty(String) System.getProperty} 1060 * @see java.lang.System#getProperty(java.lang.String) 1061 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1062 */ 1063 public static Long getLong(String nm) { 1064 return getLong(nm, null); 1065 } 1066 1067 /** 1068 * Determines the {@code long} value of the system property 1069 * with the specified name. 1070 * 1071 * <p>The first argument is treated as the name of a system 1072 * property. System properties are accessible through the {@link 1073 * java.lang.System#getProperty(java.lang.String)} method. The 1074 * string value of this property is then interpreted as a {@code 1075 * long} value using the grammar supported by {@link Long#decode decode} 1076 * and a {@code Long} object representing this value is returned. 1077 * 1078 * <p>The second argument is the default value. A {@code Long} object 1079 * that represents the value of the second argument is returned if there 1080 * is no property of the specified name, if the property does not have 1081 * the correct numeric format, or if the specified name is empty or null. 1082 * 1083 * <p>In other words, this method returns a {@code Long} object equal 1084 * to the value of: 1085 * 1086 * <blockquote> 1087 * {@code getLong(nm, new Long(val))} 1088 * </blockquote> 1089 * 1090 * but in practice it may be implemented in a manner such as: 1091 * 1092 * <blockquote><pre> 1093 * Long result = getLong(nm, null); 1094 * return (result == null) ? new Long(val) : result; 1095 * </pre></blockquote> 1096 * 1097 * to avoid the unnecessary allocation of a {@code Long} object when 1098 * the default value is not needed. 1099 * 1100 * @param nm property name. 1101 * @param val default value. 1102 * @return the {@code Long} value of the property. 1103 * @throws SecurityException for the same reasons as 1104 * {@link System#getProperty(String) System.getProperty} 1105 * @see java.lang.System#getProperty(java.lang.String) 1106 * @see java.lang.System#getProperty(java.lang.String, java.lang.String) 1107 */ 1108 public static Long getLong(String nm, long val) { 1109 Long result = Long.getLong(nm, null); 1110 return (result == null) ? Long.valueOf(val) : result; 1111 } 1112 1113 /** 1114 * Returns the {@code long} value of the system property with 1115 * the specified name. The first argument is treated as the name 1116 * of a system property. System properties are accessible through 1117 * the {@link java.lang.System#getProperty(java.lang.String)} 1118 * method. The string value of this property is then interpreted 1119 * as a {@code long} value, as per the 1120 * {@link Long#decode decode} method, and a {@code Long} object 1121 * representing this value is returned; in summary: 1122 * 1123 * <ul> 1124 * <li>If the property value begins with the two ASCII characters 1125 * {@code 0x} or the ASCII character {@code #}, not followed by 1126 * a minus sign, then the rest of it is parsed as a hexadecimal integer 1127 * exactly as for the method {@link #valueOf(java.lang.String, int)} 1128 * with radix 16. 1129 * <li>If the property value begins with the ASCII character 1130 * {@code 0} followed by another character, it is parsed as 1131 * an octal integer exactly as by the method {@link 1132 * #valueOf(java.lang.String, int)} with radix 8. 1133 * <li>Otherwise the property value is parsed as a decimal 1134 * integer exactly as by the method 1135 * {@link #valueOf(java.lang.String, int)} with radix 10. 1136 * </ul> 1137 * 1138 * <p>Note that, in every case, neither {@code L} 1139 * ({@code ‘\u005Cu004C‘}) nor {@code l} 1140 * ({@code ‘\u005Cu006C‘}) is permitted to appear at the end 1141 * of the property value as a type indicator, as would be 1142 * permitted in Java programming language source code. 1143 * 1144 * <p>The second argument is the default value. The default value is 1145 * returned if there is no property of the specified name, if the 1146 * property does not have the correct numeric format, or if the 1147 * specified name is empty or {@code null}. 1148 * 1149 * @param nm property name. 1150 * @param val default value. 1151 * @return the {@code Long} value of the property. 1152 * @throws SecurityException for the same reasons as 1153 * {@link System#getProperty(String) System.getProperty} 1154 * @see System#getProperty(java.lang.String) 1155 * @see System#getProperty(java.lang.String, java.lang.String) 1156 */ 1157 public static Long getLong(String nm, Long val) { 1158 String v = null; 1159 try { 1160 v = System.getProperty(nm); 1161 } catch (IllegalArgumentException | NullPointerException e) { 1162 } 1163 if (v != null) { 1164 try { 1165 return Long.decode(v); 1166 } catch (NumberFormatException e) { 1167 } 1168 } 1169 return val; 1170 } 1171 1172 /** 1173 * Compares two {@code Long} objects numerically. 1174 * 1175 * @param anotherLong the {@code Long} to be compared. 1176 * @return the value {@code 0} if this {@code Long} is 1177 * equal to the argument {@code Long}; a value less than 1178 * {@code 0} if this {@code Long} is numerically less 1179 * than the argument {@code Long}; and a value greater 1180 * than {@code 0} if this {@code Long} is numerically 1181 * greater than the argument {@code Long} (signed 1182 * comparison). 1183 * @since 1.2 1184 */ 1185 public int compareTo(Long anotherLong) { 1186 return compare(this.value, anotherLong.value); 1187 } 1188 1189 /** 1190 * Compares two {@code long} values numerically. 1191 * The value returned is identical to what would be returned by: 1192 * <pre> 1193 * Long.valueOf(x).compareTo(Long.valueOf(y)) 1194 * </pre> 1195 * 1196 * @param x the first {@code long} to compare 1197 * @param y the second {@code long} to compare 1198 * @return the value {@code 0} if {@code x == y}; 1199 * a value less than {@code 0} if {@code x < y}; and 1200 * a value greater than {@code 0} if {@code x > y} 1201 * @since 1.7 1202 */ 1203 public static int compare(long x, long y) { 1204 return (x < y) ? -1 : ((x == y) ? 0 : 1); 1205 } 1206 1207 /** 1208 * Compares two {@code long} values numerically treating the values 1209 * as unsigned. 1210 * 1211 * @param x the first {@code long} to compare 1212 * @param y the second {@code long} to compare 1213 * @return the value {@code 0} if {@code x == y}; a value less 1214 * than {@code 0} if {@code x < y} as unsigned values; and 1215 * a value greater than {@code 0} if {@code x > y} as 1216 * unsigned values 1217 * @since 1.8 1218 */ 1219 public static int compareUnsigned(long x, long y) { 1220 return compare(x + MIN_VALUE, y + MIN_VALUE); 1221 } 1222 1223 1224 /** 1225 * Returns the unsigned quotient of dividing the first argument by 1226 * the second where each argument and the result is interpreted as 1227 * an unsigned value. 1228 * 1229 * <p>Note that in two‘s complement arithmetic, the three other 1230 * basic arithmetic operations of add, subtract, and multiply are 1231 * bit-wise identical if the two operands are regarded as both 1232 * being signed or both being unsigned. Therefore separate {@code 1233 * addUnsigned}, etc. methods are not provided. 1234 * 1235 * @param dividend the value to be divided 1236 * @param divisor the value doing the dividing 1237 * @return the unsigned quotient of the first argument divided by 1238 * the second argument 1239 * @see #remainderUnsigned 1240 * @since 1.8 1241 */ 1242 public static long divideUnsigned(long dividend, long divisor) { 1243 if (divisor < 0L) { // signed comparison 1244 // Answer must be 0 or 1 depending on relative magnitude 1245 // of dividend and divisor. 1246 return (compareUnsigned(dividend, divisor)) < 0 ? 0L :1L; 1247 } 1248 1249 if (dividend > 0) // Both inputs non-negative 1250 return dividend/divisor; 1251 else { 1252 /* 1253 * For simple code, leveraging BigInteger. Longer and faster 1254 * code written directly in terms of operations on longs is 1255 * possible; see "Hacker‘s Delight" for divide and remainder 1256 * algorithms. 1257 */ 1258 return toUnsignedBigInteger(dividend). 1259 divide(toUnsignedBigInteger(divisor)).longValue(); 1260 } 1261 } 1262 1263 /** 1264 * Returns the unsigned remainder from dividing the first argument 1265 * by the second where each argument and the result is interpreted 1266 * as an unsigned value. 1267 * 1268 * @param dividend the value to be divided 1269 * @param divisor the value doing the dividing 1270 * @return the unsigned remainder of the first argument divided by 1271 * the second argument 1272 * @see #divideUnsigned 1273 * @since 1.8 1274 */ 1275 public static long remainderUnsigned(long dividend, long divisor) { 1276 if (dividend > 0 && divisor > 0) { // signed comparisons 1277 return dividend % divisor; 1278 } else { 1279 if (compareUnsigned(dividend, divisor) < 0) // Avoid explicit check for 0 divisor 1280 return dividend; 1281 else 1282 return toUnsignedBigInteger(dividend). 1283 remainder(toUnsignedBigInteger(divisor)).longValue(); 1284 } 1285 } 1286 1287 // Bit Twiddling 1288 1289 /** 1290 * The number of bits used to represent a {@code long} value in two‘s 1291 * complement binary form. 1292 * 1293 * @since 1.5 1294 */ 1295 @Native public static final int SIZE = 64; 1296 1297 /** 1298 * The number of bytes used to represent a {@code long} value in two‘s 1299 * complement binary form. 1300 * 1301 * @since 1.8 1302 */ 1303 public static final int BYTES = SIZE / Byte.SIZE; 1304 1305 /** 1306 * Returns a {@code long} value with at most a single one-bit, in the 1307 * position of the highest-order ("leftmost") one-bit in the specified 1308 * {@code long} value. Returns zero if the specified value has no 1309 * one-bits in its two‘s complement binary representation, that is, if it 1310 * is equal to zero. 1311 * 1312 * @param i the value whose highest one bit is to be computed 1313 * @return a {@code long} value with a single one-bit, in the position 1314 * of the highest-order one-bit in the specified value, or zero if 1315 * the specified value is itself equal to zero. 1316 * @since 1.5 1317 */ 1318 public static long highestOneBit(long i) { 1319 // HD, Figure 3-1 1320 i |= (i >> 1); 1321 i |= (i >> 2); 1322 i |= (i >> 4); 1323 i |= (i >> 8); 1324 i |= (i >> 16); 1325 i |= (i >> 32); 1326 return i - (i >>> 1); 1327 } 1328 1329 /** 1330 * Returns a {@code long} value with at most a single one-bit, in the 1331 * position of the lowest-order ("rightmost") one-bit in the specified 1332 * {@code long} value. Returns zero if the specified value has no 1333 * one-bits in its two‘s complement binary representation, that is, if it 1334 * is equal to zero. 1335 * 1336 * @param i the value whose lowest one bit is to be computed 1337 * @return a {@code long} value with a single one-bit, in the position 1338 * of the lowest-order one-bit in the specified value, or zero if 1339 * the specified value is itself equal to zero. 1340 * @since 1.5 1341 */ 1342 public static long lowestOneBit(long i) { 1343 // HD, Section 2-1 1344 return i & -i; 1345 } 1346 1347 /** 1348 * Returns the number of zero bits preceding the highest-order 1349 * ("leftmost") one-bit in the two‘s complement binary representation 1350 * of the specified {@code long} value. Returns 64 if the 1351 * specified value has no one-bits in its two‘s complement representation, 1352 * in other words if it is equal to zero. 1353 * 1354 * <p>Note that this method is closely related to the logarithm base 2. 1355 * For all positive {@code long} values x: 1356 * <ul> 1357 * <li>floor(log<sub>2</sub>(x)) = {@code 63 - numberOfLeadingZeros(x)} 1358 * <li>ceil(log<sub>2</sub>(x)) = {@code 64 - numberOfLeadingZeros(x - 1)} 1359 * </ul> 1360 * 1361 * @param i the value whose number of leading zeros is to be computed 1362 * @return the number of zero bits preceding the highest-order 1363 * ("leftmost") one-bit in the two‘s complement binary representation 1364 * of the specified {@code long} value, or 64 if the value 1365 * is equal to zero. 1366 * @since 1.5 1367 */ 1368 public static int numberOfLeadingZeros(long i) { 1369 // HD, Figure 5-6 1370 if (i == 0) 1371 return 64; 1372 int n = 1; 1373 int x = (int)(i >>> 32); 1374 if (x == 0) { n += 32; x = (int)i; } 1375 if (x >>> 16 == 0) { n += 16; x <<= 16; } 1376 if (x >>> 24 == 0) { n += 8; x <<= 8; } 1377 if (x >>> 28 == 0) { n += 4; x <<= 4; } 1378 if (x >>> 30 == 0) { n += 2; x <<= 2; } 1379 n -= x >>> 31; 1380 return n; 1381 } 1382 1383 /** 1384 * Returns the number of zero bits following the lowest-order ("rightmost") 1385 * one-bit in the two‘s complement binary representation of the specified 1386 * {@code long} value. Returns 64 if the specified value has no 1387 * one-bits in its two‘s complement representation, in other words if it is 1388 * equal to zero. 1389 * 1390 * @param i the value whose number of trailing zeros is to be computed 1391 * @return the number of zero bits following the lowest-order ("rightmost") 1392 * one-bit in the two‘s complement binary representation of the 1393 * specified {@code long} value, or 64 if the value is equal 1394 * to zero. 1395 * @since 1.5 1396 */ 1397 public static int numberOfTrailingZeros(long i) { 1398 // HD, Figure 5-14 1399 int x, y; 1400 if (i == 0) return 64; 1401 int n = 63; 1402 y = (int)i; if (y != 0) { n = n -32; x = y; } else x = (int)(i>>>32); 1403 y = x <<16; if (y != 0) { n = n -16; x = y; } 1404 y = x << 8; if (y != 0) { n = n - 8; x = y; } 1405 y = x << 4; if (y != 0) { n = n - 4; x = y; } 1406 y = x << 2; if (y != 0) { n = n - 2; x = y; } 1407 return n - ((x << 1) >>> 31); 1408 } 1409 1410 /** 1411 * Returns the number of one-bits in the two‘s complement binary 1412 * representation of the specified {@code long} value. This function is 1413 * sometimes referred to as the <i>population count</i>. 1414 * 1415 * @param i the value whose bits are to be counted 1416 * @return the number of one-bits in the two‘s complement binary 1417 * representation of the specified {@code long} value. 1418 * @since 1.5 1419 */ 1420 public static int bitCount(long i) { 1421 // HD, Figure 5-14 1422 i = i - ((i >>> 1) & 0x5555555555555555L); 1423 i = (i & 0x3333333333333333L) + ((i >>> 2) & 0x3333333333333333L); 1424 i = (i + (i >>> 4)) & 0x0f0f0f0f0f0f0f0fL; 1425 i = i + (i >>> 8); 1426 i = i + (i >>> 16); 1427 i = i + (i >>> 32); 1428 return (int)i & 0x7f; 1429 } 1430 1431 /** 1432 * Returns the value obtained by rotating the two‘s complement binary 1433 * representation of the specified {@code long} value left by the 1434 * specified number of bits. (Bits shifted out of the left hand, or 1435 * high-order, side reenter on the right, or low-order.) 1436 * 1437 * <p>Note that left rotation with a negative distance is equivalent to 1438 * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val, 1439 * distance)}. Note also that rotation by any multiple of 64 is a 1440 * no-op, so all but the last six bits of the rotation distance can be 1441 * ignored, even if the distance is negative: {@code rotateLeft(val, 1442 * distance) == rotateLeft(val, distance & 0x3F)}. 1443 * 1444 * @param i the value whose bits are to be rotated left 1445 * @param distance the number of bit positions to rotate left 1446 * @return the value obtained by rotating the two‘s complement binary 1447 * representation of the specified {@code long} value left by the 1448 * specified number of bits. 1449 * @since 1.5 1450 */ 1451 public static long rotateLeft(long i, int distance) { 1452 return (i << distance) | (i >>> -distance); 1453 } 1454 1455 /** 1456 * Returns the value obtained by rotating the two‘s complement binary 1457 * representation of the specified {@code long} value right by the 1458 * specified number of bits. (Bits shifted out of the right hand, or 1459 * low-order, side reenter on the left, or high-order.) 1460 * 1461 * <p>Note that right rotation with a negative distance is equivalent to 1462 * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val, 1463 * distance)}. Note also that rotation by any multiple of 64 is a 1464 * no-op, so all but the last six bits of the rotation distance can be 1465 * ignored, even if the distance is negative: {@code rotateRight(val, 1466 * distance) == rotateRight(val, distance & 0x3F)}. 1467 * 1468 * @param i the value whose bits are to be rotated right 1469 * @param distance the number of bit positions to rotate right 1470 * @return the value obtained by rotating the two‘s complement binary 1471 * representation of the specified {@code long} value right by the 1472 * specified number of bits. 1473 * @since 1.5 1474 */ 1475 public static long rotateRight(long i, int distance) { 1476 return (i >>> distance) | (i << -distance); 1477 } 1478 1479 /** 1480 * Returns the value obtained by reversing the order of the bits in the 1481 * two‘s complement binary representation of the specified {@code long} 1482 * value. 1483 * 1484 * @param i the value to be reversed 1485 * @return the value obtained by reversing order of the bits in the 1486 * specified {@code long} value. 1487 * @since 1.5 1488 */ 1489 public static long reverse(long i) { 1490 // HD, Figure 7-1 1491 i = (i & 0x5555555555555555L) << 1 | (i >>> 1) & 0x5555555555555555L; 1492 i = (i & 0x3333333333333333L) << 2 | (i >>> 2) & 0x3333333333333333L; 1493 i = (i & 0x0f0f0f0f0f0f0f0fL) << 4 | (i >>> 4) & 0x0f0f0f0f0f0f0f0fL; 1494 i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; 1495 i = (i << 48) | ((i & 0xffff0000L) << 16) | 1496 ((i >>> 16) & 0xffff0000L) | (i >>> 48); 1497 return i; 1498 } 1499 1500 /** 1501 * Returns the signum function of the specified {@code long} value. (The 1502 * return value is -1 if the specified value is negative; 0 if the 1503 * specified value is zero; and 1 if the specified value is positive.) 1504 * 1505 * @param i the value whose signum is to be computed 1506 * @return the signum function of the specified {@code long} value. 1507 * @since 1.5 1508 */ 1509 public static int signum(long i) { 1510 // HD, Section 2-7 1511 return (int) ((i >> 63) | (-i >>> 63)); 1512 } 1513 1514 /** 1515 * Returns the value obtained by reversing the order of the bytes in the 1516 * two‘s complement representation of the specified {@code long} value. 1517 * 1518 * @param i the value whose bytes are to be reversed 1519 * @return the value obtained by reversing the bytes in the specified 1520 * {@code long} value. 1521 * @since 1.5 1522 */ 1523 public static long reverseBytes(long i) { 1524 i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL; 1525 return (i << 48) | ((i & 0xffff0000L) << 16) | 1526 ((i >>> 16) & 0xffff0000L) | (i >>> 48); 1527 } 1528 1529 /** 1530 * Adds two {@code long} values together as per the + operator. 1531 * 1532 * @param a the first operand 1533 * @param b the second operand 1534 * @return the sum of {@code a} and {@code b} 1535 * @see java.util.function.BinaryOperator 1536 * @since 1.8 1537 */ 1538 public static long sum(long a, long b) { 1539 return a + b; 1540 } 1541 1542 /** 1543 * Returns the greater of two {@code long} values 1544 * as if by calling {@link Math#max(long, long) Math.max}. 1545 * 1546 * @param a the first operand 1547 * @param b the second operand 1548 * @return the greater of {@code a} and {@code b} 1549 * @see java.util.function.BinaryOperator 1550 * @since 1.8 1551 */ 1552 public static long max(long a, long b) { 1553 return Math.max(a, b); 1554 } 1555 1556 /** 1557 * Returns the smaller of two {@code long} values 1558 * as if by calling {@link Math#min(long, long) Math.min}. 1559 * 1560 * @param a the first operand 1561 * @param b the second operand 1562 * @return the smaller of {@code a} and {@code b} 1563 * @see java.util.function.BinaryOperator 1564 * @since 1.8 1565 */ 1566 public static long min(long a, long b) { 1567 return Math.min(a, b); 1568 } 1569 1570 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 1571 @Native private static final long serialVersionUID = 4290774380558885855L; 1572 }Long Source
LongCache的常量池 [-128,127] 有效值。
原文地址：https://www.cnblogs.com/aben-blog/p/8728995.html
时间： 2024-10-31 13:47:52