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java.lang
public final class: Double [javadoc | source]
java.lang.Object
   java.lang.Number
      java.lang.Double

All Implemented Interfaces:
    Comparable, Serializable

The {@code Double} class wraps a value of the primitive type {@code double} in an object. An object of type {@code Double} contains a single field whose type is {@code double}.

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}.

Field Summary
public static final  double POSITIVE_INFINITY    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 NEGATIVE_INFINITY    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 NaN    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 MAX_VALUE    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 MIN_NORMAL    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_VALUE    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  int MAX_EXPONENT    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 MIN_EXPONENT    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 SIZE    The number of bits used to represent a {@code double} value.
    since: 1.5 -
 
public static final  Class<Double> TYPE    The {@code Class} instance representing the primitive type {@code double}.
    since: JDK1.1 -
 
Constructor:
 public Double(double value) 
 public Double(String s) throws NumberFormatException 
    Constructs a newly allocated {@code Double} object that represents the floating-point value of type {@code double} represented by the string. The string is converted to a {@code double} value as if by the {@code valueOf} method.
    Parameters:
    s - a string to be converted to a {@code Double}.
    Throws:
    NumberFormatException - if the string does not contain a parsable number.
    Also see:
    java.lang.Double#valueOf(java.lang.String)
Method from java.lang.Double Summary:
byteValue,   compare,   compareTo,   doubleToLongBits,   doubleToRawLongBits,   doubleValue,   equals,   floatValue,   hashCode,   intValue,   isInfinite,   isInfinite,   isNaN,   isNaN,   longBitsToDouble,   longValue,   parseDouble,   shortValue,   toHexString,   toString,   toString,   valueOf,   valueOf
Methods from java.lang.Number:
byteValue,   doubleValue,   floatValue,   intValue,   longValue,   shortValue
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.lang.Double Detail:
 public byte byteValue() 
    Returns the value of this {@code Double} as a {@code byte} (by casting to a {@code byte}).
 public static int compare(double d1,
    double d2) 
    Compares the two specified {@code double} values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:
       new Double(d1).compareTo(new Double(d2))
    
 public int compareTo(Double anotherDouble) 
    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}.
    This ensures that the natural ordering of {@code Double} objects imposed by this method is consistent with equals.
 public static long doubleToLongBits(double value) 
    Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.

    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 #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).

 public static native long doubleToRawLongBits(double value)
    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 #longBitsToDouble(long) method, will produce a floating-point value the same as the argument to {@code doubleToRawLongBits}.

 public double doubleValue() 
    Returns the {@code double} value of this {@code Double} object.
 public boolean equals(Object obj) 
    Compares this object against the specified object. The result is {@code true} if and only if the argument is not {@code null} and is a {@code Double} object that represents a {@code double} that has the same value as the {@code double} represented by this object. For this purpose, two {@code double} values are considered to be the same if and only if the method #doubleToLongBits(double) returns the identical {@code long} value when applied to each.

    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}.
    This definition allows hash tables to operate properly.
 public float floatValue() 
    Returns the {@code float} value of this {@code Double} object.
 public int hashCode() 
    Returns a hash code for this {@code Double} object. The result is the exclusive OR of the two halves of the {@code long} integer bit representation, exactly as produced by the method #doubleToLongBits(double) , of the primitive {@code double} value represented by this {@code Double} object. That is, the hash code is the value of the expression:
    {@code (int)(v^(v>>>32))}
    where {@code v} is defined by:
    {@code long v = Double.doubleToLongBits(this.doubleValue());}
 public int intValue() 
    Returns the value of this {@code Double} as an {@code int} (by casting to type {@code int}).
 public boolean isInfinite() 
    Returns {@code true} if this {@code Double} value is infinitely large in magnitude, {@code false} otherwise.
 public static boolean isInfinite(double v) 
    Returns {@code true} if the specified number is infinitely large in magnitude, {@code false} otherwise.
 public boolean isNaN() 
    Returns {@code true} if this {@code Double} value is a Not-a-Number (NaN), {@code false} otherwise.
 public static boolean isNaN(double v) 
    Returns {@code true} if the specified number is a Not-a-Number (NaN) value, {@code false} otherwise.
 public static native double longBitsToDouble(long bits)
    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:

    int s = ((bits >> 63) == 0) ? 1 : -1;
    int e = (int)((bits >> 52) & 0x7ffL);
    long m = (e == 0) ?
                    (bits & 0xfffffffffffffL) << 1 :
                    (bits & 0xfffffffffffffL) | 0x10000000000000L;
    
    Then the floating-point result equals the value of the mathematical expression s·m·2e-1075.

    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.

 public long longValue() 
    Returns the value of this {@code Double} as a {@code long} (by casting to type {@code long}).
 public static double parseDouble(String s) throws NumberFormatException 
    Returns a new {@code double} initialized to the value represented by the specified {@code String}, as performed by the {@code valueOf} method of class {@code Double}.
 public short shortValue() 
    Returns the value of this {@code Double} as a {@code short} (by casting to a {@code short}).
 public static String toHexString(double 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 -}' ('\u002D'); 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 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.

    Examples

    Floating-point ValueHexadecimal String
    {@code 1.0} {@code 0x1.0p0}
    {@code -1.0} {@code -0x1.0p0}
    {@code 2.0} {@code 0x1.0p1}
    {@code 3.0} {@code 0x1.8p1}
    {@code 0.5} {@code 0x1.0p-1}
    {@code 0.25} {@code 0x1.0p-2}
    {@code Double.MAX_VALUE} {@code 0x1.fffffffffffffp1023}
    {@code Minimum Normal Value} {@code 0x1.0p-1022}
    {@code Maximum Subnormal Value} {@code 0x0.fffffffffffffp-1022}
    {@code Double.MIN_VALUE} {@code 0x0.0000000000001p-1022}
 public String toString() 
    Returns a string representation of this {@code Double} object. The primitive {@code double} value represented by this object is converted to a string exactly as if by the method {@code toString} of one argument.
 public static String toString(double d) 
    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 -}' ('\u002D'); 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 .}' ('\u002E'), 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 10nm {@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 .}' ('\u002E'), followed by decimal digits representing the fractional part of a, followed by the letter '{@code E}' ('\u0045'), followed by a representation of n as a decimal integer, as produced by the method Integer#toString(int) .
    How many digits must be printed for the fractional part of m or a? There must be at least one digit to represent the fractional part, and beyond that as many, but only as many, more digits as are needed to uniquely distinguish the argument value from adjacent values of type {@code double}. That is, suppose that x is the exact mathematical value represented by the decimal representation produced by this method for a finite nonzero argument d. Then d must be the {@code double} value nearest to x; or if two {@code double} values are equally close to x, then d must be one of them and the least significant bit of the significand of d must be {@code 0}.

    To create localized string representations of a floating-point value, use subclasses of java.text.NumberFormat .

 public static Double valueOf(String s) throws NumberFormatException 
    Returns a {@code Double} object holding the {@code double} value represented by the argument string {@code s}.

    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 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:
    Signopt {@code NaN}
    Signopt {@code Infinity}
    Signopt FloatingPointLiteral
    Signopt HexFloatingPointLiteral
    SignedInteger

    HexFloatingPointLiteral:
    HexSignificand BinaryExponent FloatTypeSuffixopt

    HexSignificand:
    HexNumeral
    HexNumeral {@code .}
    {@code 0x} HexDigitsopt {@code .} HexDigits
    {@code 0X} HexDigitsopt {@code .} HexDigits

    BinaryExponent:
    BinaryExponentIndicator SignedInteger

    BinaryExponentIndicator:
    {@code p}
    {@code P}
    where Sign, FloatingPointLiteral, HexNumeral, HexDigits, SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of The Java™ Language Specification, except that underscores are not accepted between digits. If {@code s} does not have the form of a FloatValue, then a {@code NumberFormatException} is thrown. Otherwise, {@code s} is regarded as representing an exact decimal value in the usual "computerized scientific notation" or as an exact hexadecimal value; this exact numerical value is then conceptually converted to an "infinitely precise" binary value that is then rounded to type {@code double} by the usual round-to-nearest rule of IEEE 754 floating-point arithmetic, which includes preserving the sign of a zero value. Note that the round-to-nearest rule also implies overflow and underflow behaviour; if the exact value of {@code s} is large enough in magnitude (greater than or equal to (#MAX_VALUE + ulp(MAX_VALUE) /2), rounding to {@code double} will result in an infinity and if the exact value of {@code s} is small enough in magnitude (less than or equal to #MIN_VALUE /2), rounding to float will result in a zero. Finally, after rounding a {@code Double} object representing this {@code double} value is returned.

    To interpret localized string representations of a floating-point value, use subclasses of 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:

     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
     }
    
 public static Double valueOf(double d) 
    Returns a {@code Double} instance representing the specified {@code double} value. If a new {@code Double} instance is not required, this method should generally be used in preference to the constructor #Double(double) , as this method is likely to yield significantly better space and time performance by caching frequently requested values.