In addition, this class provides several methods for converting a * {@code double} to a {@code String} and a * {@code String} to a {@code double}, as well as other * constants and methods useful when dealing with a * {@code double}. * * @author Lee Boynton * @author Arthur van Hoff * @author Joseph D. Darcy * @since JDK1.0 */ public final class Double extends Number implements Comparable { /** * A constant holding the positive infinity of type * {@code double}. It is equal to the value returned by * {@code Double.longBitsToDouble(0x7ff0000000000000L)}. */ public static final double POSITIVE_INFINITY = 1.0 / 0.0; /** * A constant holding the negative infinity of type * {@code double}. It is equal to the value returned by * {@code Double.longBitsToDouble(0xfff0000000000000L)}. */ public static final double NEGATIVE_INFINITY = -1.0 / 0.0; /** * A constant holding a Not-a-Number (NaN) value of type * {@code double}. It is equivalent to the value returned by * {@code Double.longBitsToDouble(0x7ff8000000000000L)}. */ public static final double NaN = 0.0d / 0.0; /** * A constant holding the largest positive finite value of type * {@code double}, * (2-2^-52)·2¹⁰²³. It is equal to * the hexadecimal floating-point literal * {@code 0x1.fffffffffffffP+1023} and also equal to * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}. */ public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308 /** * A constant holding the smallest positive normal value of type * {@code double}, 2^-1022. It is equal to the * hexadecimal floating-point literal {@code 0x1.0p-1022} and also * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}. * * @since 1.6 */ public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308 /** * A constant holding the smallest positive nonzero value of type * {@code double}, 2^-1074. It is equal to the * hexadecimal floating-point literal * {@code 0x0.0000000000001P-1022} and also equal to * {@code Double.longBitsToDouble(0x1L)}. */ public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324 /** * Maximum exponent a finite {@code double} variable may have. * It is equal to the value returned by * {@code Math.getExponent(Double.MAX_VALUE)}. * * @since 1.6 */ public static final int MAX_EXPONENT = 1023; /** * Minimum exponent a normalized {@code double} variable may * have. It is equal to the value returned by * {@code Math.getExponent(Double.MIN_NORMAL)}. * * @since 1.6 */ public static final int MIN_EXPONENT = -1022; /** * The number of bits used to represent a {@code double} value. * * @since 1.5 */ public static final int SIZE = 64; /** * The number of bytes used to represent a {@code double} value. * * @since 1.8 */ public static final int BYTES = SIZE / Byte.SIZE; /** * The {@code Class} instance representing the primitive type * {@code double}. * * @since JDK1.1 */ @SuppressWarnings("unchecked") public static final Class TYPE = (Class) Class.getPrimitiveClass("double"); /** * Returns a string representation of the {@code double} * argument. All characters mentioned below are ASCII characters. *

*
• If the argument is NaN, the result is the string * "{@code NaN}". *
• Otherwise, the result is a string that represents the sign and * magnitude (absolute value) of the argument. If the sign is negative, * the first character of the result is '{@code -}' * ({@code '\u005Cu002D'}); if the sign is positive, no sign character * appears in the result. As for the magnitude m: *
  *
  • If m is infinity, it is represented by the characters * {@code "Infinity"}; thus, positive infinity produces the result * {@code "Infinity"} and negative infinity produces the result * {@code "-Infinity"}. * *
  • If m is zero, it is represented by the characters * {@code "0.0"}; thus, negative zero produces the result * {@code "-0.0"} and positive zero produces the result * {@code "0.0"}. * *
  • If m is greater than or equal to 10^-3 but less * than 10⁷, then it is represented as the integer part of * m, in decimal form with no leading zeroes, followed by * '{@code .}' ({@code '\u005Cu002E'}), followed by one or * more decimal digits representing the fractional part of m. * *
  • If m is less than 10^-3 or greater than or * equal to 10⁷, then it is represented in so-called * "computerized scientific notation." Let n be the unique * integer such that 10ⁿ ≤ m {@literal <} * 10ⁿ⁺¹; then let a be the * mathematically exact quotient of m and * 10ⁿ so that 1 ≤ a {@literal <} 10. The * magnitude is then represented as the integer part of a, * as a single decimal digit, followed by '{@code .}' * ({@code '\u005Cu002E'}), followed by decimal digits * representing the fractional part of a, followed by the * letter '{@code E}' ({@code '\u005Cu0045'}), followed * by a representation of n as a decimal integer, as * produced by the method {@link Integer#toString(int)}. *
  *

To create localized string representations of a floating-point * value, use subclasses of {@link java.text.NumberFormat}. * * @param d the {@code double} to be converted. * @return a string representation of the argument. */ public static String toString(double d) { return FloatingDecimal.toJavaFormatString(d); } /** * Returns a hexadecimal string representation of the * {@code double} argument. All characters mentioned below * are ASCII characters. * *

*
• If the argument is NaN, the result is the string * "{@code NaN}". *
• Otherwise, the result is a string that represents the sign * and magnitude of the argument. If the sign is negative, the * first character of the result is '{@code -}' * ({@code '\u005Cu002D'}); if the sign is positive, no sign * character appears in the result. As for the magnitude m: * *
  *
  • If m is infinity, it is represented by the string * {@code "Infinity"}; thus, positive infinity produces the * result {@code "Infinity"} and negative infinity produces * the result {@code "-Infinity"}. * *
  • If m is zero, it is represented by the string * {@code "0x0.0p0"}; thus, negative zero produces the result * {@code "-0x0.0p0"} and positive zero produces the result * {@code "0x0.0p0"}. * *
  • If m is a {@code double} value with a * normalized representation, substrings are used to represent the * significand and exponent fields. The significand is * represented by the characters {@code "0x1."} * followed by a lowercase hexadecimal representation of the rest * of the significand as a fraction. Trailing zeros in the * hexadecimal representation are removed unless all the digits * are zero, in which case a single zero is used. Next, the * exponent is represented by {@code "p"} followed * by a decimal string of the unbiased exponent as if produced by * a call to {@link Integer#toString(int) Integer.toString} on the * exponent value. * *
  • If m is a {@code double} value with a subnormal * representation, the significand is represented by the * characters {@code "0x0."} followed by a * hexadecimal representation of the rest of the significand as a * fraction. Trailing zeros in the hexadecimal representation are * removed. Next, the exponent is represented by * {@code "p-1022"}. Note that there must be at * least one nonzero digit in a subnormal significand. * *
  * *

If {@code s} is {@code null}, then a * {@code NullPointerException} is thrown. * *

Leading and trailing whitespace characters in {@code s} * are ignored. Whitespace is removed as if by the {@link * String#trim} method; that is, both ASCII space and control * characters are removed. The rest of {@code s} should * constitute a FloatValue as described by the lexical * syntax rules: * *

*

*

FloatValue: *

Sign_opt {@code NaN} *

Sign_opt {@code Infinity} *

Sign_opt FloatingPointLiteral *

Sign_opt HexFloatingPointLiteral *

SignedInteger *

* *

*

HexFloatingPointLiteral: *

HexSignificand BinaryExponent FloatTypeSuffix_opt *

* *

*

HexSignificand: *

HexNumeral *

HexNumeral {@code .} *

{@code 0x} HexDigits_opt * {@code .} HexDigits *

{@code 0X} HexDigits_opt * {@code .} HexDigits *

* *

*

BinaryExponent: *

BinaryExponentIndicator SignedInteger *

* *

*

BinaryExponentIndicator: *

{@code p} *

{@code P} *

* *

To interpret localized string representations of a * floating-point value, use subclasses of {@link * java.text.NumberFormat}. * *

Note that trailing format specifiers, specifiers that * determine the type of a floating-point literal * ({@code 1.0f} is a {@code float} value; * {@code 1.0d} is a {@code double} value), do * not influence the results of this method. In other * words, the numerical value of the input string is converted * directly to the target floating-point type. The two-step * sequence of conversions, string to {@code float} followed * by {@code float} to {@code double}, is not * equivalent to converting a string directly to * {@code double}. For example, the {@code float} * literal {@code 0.1f} is equal to the {@code double} * value {@code 0.10000000149011612}; the {@code float} * literal {@code 0.1f} represents a different numerical * value than the {@code double} literal * {@code 0.1}. (The numerical value 0.1 cannot be exactly * represented in a binary floating-point number.) * *

To avoid calling this method on an invalid string and having * a {@code NumberFormatException} be thrown, the regular * expression below can be used to screen the input string: * *

{@code
     *  final String Digits     = "(\\p{Digit}+)";
     *  final String HexDigits  = "(\\p{XDigit}+)";
     *  // an exponent is 'e' or 'E' followed by an optionally
     *  // signed decimal integer.
     *  final String Exp        = "[eE][+-]?"+Digits;
     *  final String fpRegex    =
     *      ("[\\x00-\\x20]*"+  // Optional leading "whitespace"
     *       "[+-]?(" + // Optional sign character
     *       "NaN|" +           // "NaN" string
     *       "Infinity|" +      // "Infinity" string
     *
     *       // A decimal floating-point string representing a finite positive
     *       // number without a leading sign has at most five basic pieces:
     *       // Digits . Digits ExponentPart FloatTypeSuffix
     *       //
     *       // Since this method allows integer-only strings as input
     *       // in addition to strings of floating-point literals, the
     *       // two sub-patterns below are simplifications of the grammar
     *       // productions from section 3.10.2 of
     *       // The Java Language Specification.
     *
     *       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
     *       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
     *
     *       // . Digits ExponentPart_opt FloatTypeSuffix_opt
     *       "(\\.("+Digits+")("+Exp+")?)|"+
     *
     *       // Hexadecimal strings
     *       "((" +
     *        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
     *        "(0[xX]" + HexDigits + "(\\.)?)|" +
     *
     *        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
     *        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
     *
     *        ")[pP][+-]?" + Digits + "))" +
     *       "[fFdD]?))" +
     *       "[\\x00-\\x20]*");// Optional trailing "whitespace"
     *
     *  if (Pattern.matches(fpRegex, myString))
     *      Double.valueOf(myString); // Will not throw NumberFormatException
     *  else {
     *      // Perform suitable alternative action
     *  }
     * }

* {@code (int)(v^(v>>>32))} *

* {@code long v = Double.doubleToLongBits(this.doubleValue());} *

Note that in most cases, for two instances of class * {@code Double}, {@code d1} and {@code d2}, the * value of {@code d1.equals(d2)} is {@code true} if and * only if * *

* {@code d1.doubleValue() == d2.doubleValue()} *

also has the value {@code true}. However, there are two * exceptions: *

*
• If {@code d1} and {@code d2} both represent * {@code Double.NaN}, then the {@code equals} method * returns {@code true}, even though * {@code Double.NaN==Double.NaN} has the value * {@code false}. *
• If {@code d1} represents {@code +0.0} while * {@code d2} represents {@code -0.0}, or vice versa, * the {@code equal} test has the value {@code false}, * even though {@code +0.0==-0.0} has the value {@code true}. *

Bit 63 (the bit that is selected by the mask * {@code 0x8000000000000000L}) represents the sign of the * floating-point number. Bits * 62-52 (the bits that are selected by the mask * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0 * (the bits that are selected by the mask * {@code 0x000fffffffffffffL}) represent the significand * (sometimes called the mantissa) of the floating-point number. * *

If the argument is positive infinity, the result is * {@code 0x7ff0000000000000L}. * *

If the argument is negative infinity, the result is * {@code 0xfff0000000000000L}. * *

If the argument is NaN, the result is * {@code 0x7ff8000000000000L}. * *

In all cases, the result is a {@code long} integer that, when * given to the {@link #longBitsToDouble(long)} method, will produce a * floating-point value the same as the argument to * {@code doubleToLongBits} (except all NaN values are * collapsed to a single "canonical" NaN value). * * @param value a {@code double} precision floating-point number. * @return the bits that represent the floating-point number. */ public static long doubleToLongBits(double value) { long result = doubleToRawLongBits(value); // Check for NaN based on values of bit fields, maximum // exponent and nonzero significand. if ( ((result & DoubleConsts.EXP_BIT_MASK) == DoubleConsts.EXP_BIT_MASK) && (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L) result = 0x7ff8000000000000L; return result; } /** * Returns a representation of the specified floating-point value * according to the IEEE 754 floating-point "double * format" bit layout, preserving Not-a-Number (NaN) values. * *

Bit 63 (the bit that is selected by the mask * {@code 0x8000000000000000L}) represents the sign of the * floating-point number. Bits * 62-52 (the bits that are selected by the mask * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0 * (the bits that are selected by the mask * {@code 0x000fffffffffffffL}) represent the significand * (sometimes called the mantissa) of the floating-point number. * *

If the argument is positive infinity, the result is * {@code 0x7ff0000000000000L}. * *

If the argument is negative infinity, the result is * {@code 0xfff0000000000000L}. * *

If the argument is NaN, the result is the {@code long} * integer representing the actual NaN value. Unlike the * {@code doubleToLongBits} method, * {@code doubleToRawLongBits} does not collapse all the bit * patterns encoding a NaN to a single "canonical" NaN * value. * *

In all cases, the result is a {@code long} integer that, * when given to the {@link #longBitsToDouble(long)} method, will * produce a floating-point value the same as the argument to * {@code doubleToRawLongBits}. * * @param value a {@code double} precision floating-point number. * @return the bits that represent the floating-point number. * @since 1.3 */ public static native long doubleToRawLongBits(double value); /** * Returns the {@code double} value corresponding to a given * bit representation. * The argument is considered to be a representation of a * floating-point value according to the IEEE 754 floating-point * "double format" bit layout. * *

If the argument is {@code 0x7ff0000000000000L}, the result * is positive infinity. * *

If the argument is {@code 0xfff0000000000000L}, the result * is negative infinity. * *

If the argument is any value in the range * {@code 0x7ff0000000000001L} through * {@code 0x7fffffffffffffffL} or in the range * {@code 0xfff0000000000001L} through * {@code 0xffffffffffffffffL}, the result is a NaN. No IEEE * 754 floating-point operation provided by Java can distinguish * between two NaN values of the same type with different bit * patterns. Distinct values of NaN are only distinguishable by * use of the {@code Double.doubleToRawLongBits} method. * *

In all other cases, let s, e, and m be three * values that can be computed from the argument: * *

{@code
     * int s = ((bits >> 63) == 0) ? 1 : -1;
     * int e = (int)((bits >> 52) & 0x7ffL);
     * long m = (e == 0) ?
     *                 (bits & 0xfffffffffffffL) << 1 :
     *                 (bits & 0xfffffffffffffL) | 0x10000000000000L;
     * }

Note that this method may not be able to return a * {@code double} NaN with exactly same bit pattern as the * {@code long} argument. IEEE 754 distinguishes between two * kinds of NaNs, quiet NaNs and signaling NaNs. The * differences between the two kinds of NaN are generally not * visible in Java. Arithmetic operations on signaling NaNs turn * them into quiet NaNs with a different, but often similar, bit * pattern. However, on some processors merely copying a * signaling NaN also performs that conversion. In particular, * copying a signaling NaN to return it to the calling method * may perform this conversion. So {@code longBitsToDouble} * may not be able to return a {@code double} with a * signaling NaN bit pattern. Consequently, for some * {@code long} values, * {@code doubleToRawLongBits(longBitsToDouble(start))} may * not equal {@code start}. Moreover, which * particular bit patterns represent signaling NaNs is platform * dependent; although all NaN bit patterns, quiet or signaling, * must be in the NaN range identified above. * * @param bits any {@code long} integer. * @return the {@code double} floating-point value with the same * bit pattern. */ public static native double longBitsToDouble(long bits); /** * Compares two {@code Double} objects numerically. There * are two ways in which comparisons performed by this method * differ from those performed by the Java language numerical * comparison operators ({@code <, <=, ==, >=, >}) * when applied to primitive {@code double} values: *

• * {@code Double.NaN} is considered by this method * to be equal to itself and greater than all other * {@code double} values (including * {@code Double.POSITIVE_INFINITY}). *
• * {@code 0.0d} is considered by this method to be greater * than {@code -0.0d}. *

     *    new Double(d1).compareTo(new Double(d2))
     *