Double class wraps a value of the primitive type
* double in an object. An object of type
* Double contains a single field whose type is
* double.
*
* In addition, this class provides several methods for converting a
* double to a String and a
* String to a double, as well as other
* constants and methods useful when dealing with a
* double.
*
* @author Lee Boynton
* @author Arthur van Hoff
* @version 1.82, 01/23/03
* @since JDK1.0
*/
public final class Double extends Number implements Comparable {
/**
* A constant holding the positive infinity of type
* double. It is equal to the value returned by
* Double.longBitsToDouble(0x7ff0000000000000L).
*/
public static final double POSITIVE_INFINITY = 1.0 / 0.0;
/**
* A constant holding the negative infinity of type
* double. It is equal to the value returned by
* Double.longBitsToDouble(0xfff0000000000000L).
*/
public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
/**
* A constant holding a Not-a-Number (NaN) value of type
* double. It is equivalent to the value returned by
* Double.longBitsToDouble(0x7ff8000000000000L).
*/
public static final double NaN = 0.0d / 0.0;
/**
* A constant holding the largest positive finite value of type
* double, (2-2-52)·21023.
* It is equal to the value returned by:
* Double.longBitsToDouble(0x7fefffffffffffffL).
*/
public static final double MAX_VALUE = 1.7976931348623157e+308;
/**
* A constant holding the smallest positive nonzero value of type
* double, 2-1074. It is equal to the
* value returned by Double.longBitsToDouble(0x1L).
*/
public static final double MIN_VALUE = 4.9e-324;
/**
* The Class instance representing the primitive type
* double.
*
* @since JDK1.1
*/
public static final Class TYPE = Class.getPrimitiveClass("double");
/**
* Returns a string representation of the double
* argument. All characters mentioned below are ASCII characters.
*
NaN".
* -'
* ('\u002D'); if the sign is positive, no sign character
* appears in the result. As for the magnitude m:
* "Infinity"; thus, positive infinity produces the result
* "Infinity" and negative infinity produces the result
* "-Infinity".
*
* "0.0"; thus, negative zero produces the result
* "-0.0" and positive zero produces the result
* "0.0".
*
* .' ('\u002E'), followed by one or
* more decimal digits representing the fractional part of m.
*
* .'
* ('\u002E'), followed by decimal digits
* representing the fractional part of a, followed by the
* letter 'E' ('\u0045'), followed
* by a representation of n as a decimal integer, as
* produced by the method {@link Integer#toString(int)}.
* 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 double value nearest
* to x; or if two 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 0.
*
* To create localized string representations of a floating-point
* value, use subclasses of {@link java.text.NumberFormat}.
*
* @param d the double to be converted.
* @return a string representation of the argument.
*/
public static String toString(double d) {
return new FloatingDecimal(d).toJavaFormatString();
}
/**
* Returns a Double object holding the
* double value represented by the argument string
* s.
*
* If s is null, then a
* NullPointerException is thrown.
*
* Leading and trailing whitespace characters in s
* are ignored. The rest of s should constitute a
* FloatValue as described by the lexical rule:
*
** where Sign and FloatingPointLiteral are as * defined in * §3.10.2 * of the Java * Language Specification. If*
*- FloatValue: *
- Signopt
NaN*- Signopt
Infinity*- Signopt FloatingPointLiteral *
s does not have the
* form of a FloatValue, then a NumberFormatException
* is thrown. Otherwise, s is regarded as
* representing an exact decimal value in the usual "computerized
* scientific notation"; this exact decimal value is then
* conceptually converted to an "infinitely precise" binary value
* that is then rounded to type double by the usual
* round-to-nearest rule of IEEE 754 floating-point arithmetic,
* which includes preserving the sign of a zero value. Finally, a
* Double object representing this
* double value is returned.
* * 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
* (1.0f is a float value;
* 1.0d is a 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 float followed
* by float to double, is not
* equivalent to converting a string directly to
* double. For example, the float
* literal 0.1f is equal to the double
* value 0.10000000149011612; the float
* literal 0.1f represents a different numerical
* value than the double literal
* 0.1. (The numerical value 0.1 cannot be exactly
* represented in a binary floating-point number.)
*
* @param s the string to be parsed.
* @return a Double object holding the value
* represented by the String argument.
* @exception NumberFormatException if the string does not contain a
* parsable number.
*/
public static Double valueOf(String s) throws NumberFormatException {
return new Double(FloatingDecimal.readJavaFormatString(s).doubleValue());
}
/**
* Returns a new double initialized to the value
* represented by the specified String, as performed
* by the valueOf method of class
* Double.
*
* @param s the string to be parsed.
* @return the double value represented by the string
* argument.
* @exception NumberFormatException if the string does not contain
* a parsable double.
* @see java.lang.Double#valueOf(String)
* @since 1.2
*/
public static double parseDouble(String s) throws NumberFormatException {
return FloatingDecimal.readJavaFormatString(s).doubleValue();
}
/**
* Returns true if the specified number is a
* Not-a-Number (NaN) value, false otherwise.
*
* @param v the value to be tested.
* @return true if the value of the argument is NaN;
* false otherwise.
*/
static public boolean isNaN(double v) {
return (v != v);
}
/**
* Returns true if the specified number is infinitely
* large in magnitude, false otherwise.
*
* @param v the value to be tested.
* @return true if the value of the argument is positive
* infinity or negative infinity; false otherwise.
*/
static public boolean isInfinite(double v) {
return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
}
/**
* The value of the Double.
*
* @serial
*/
private double value;
/**
* Constructs a newly allocated Double object that
* represents the primitive double argument.
*
* @param value the value to be represented by the Double.
*/
public Double(double value) {
this.value = value;
}
/**
* Constructs a newly allocated Double object that
* represents the floating-point value of type double
* represented by the string. The string is converted to a
* double value as if by the valueOf method.
*
* @param s a string to be converted to a Double.
* @exception NumberFormatException if the string does not contain a
* parsable number.
* @see java.lang.Double#valueOf(java.lang.String)
*/
public Double(String s) throws NumberFormatException {
// REMIND: this is inefficient
this(valueOf(s).doubleValue());
}
/**
* Returns true if this Double value is
* a Not-a-Number (NaN), false otherwise.
*
* @return true if the value represented by this object is
* NaN; false otherwise.
*/
public boolean isNaN() {
return isNaN(value);
}
/**
* Returns true if this Double value is
* infinitely large in magnitude, false otherwise.
*
* @return true if the value represented by this object is
* positive infinity or negative infinity;
* false otherwise.
*/
public boolean isInfinite() {
return isInfinite(value);
}
/**
* Returns a string representation of this Double object.
* The primitive double value represented by this
* object is converted to a string exactly as if by the method
* toString of one argument.
*
* @return a String representation of this object.
* @see java.lang.Double#toString(double)
*/
public String toString() {
return String.valueOf(value);
}
/**
* Returns the value of this Double as a byte (by
* casting to a byte).
*
* @return the double value represented by this object
* converted to type byte
* @since JDK1.1
*/
public byte byteValue() {
return (byte)value;
}
/**
* Returns the value of this Double as a
* short (by casting to a short).
*
* @return the double value represented by this object
* converted to type short
* @since JDK1.1
*/
public short shortValue() {
return (short)value;
}
/**
* Returns the value of this Double as an
* int (by casting to type int).
*
* @return the double value represented by this object
* converted to type int
*/
public int intValue() {
return (int)value;
}
/**
* Returns the value of this Double as a
* long (by casting to type long).
*
* @return the double value represented by this object
* converted to type long
*/
public long longValue() {
return (long)value;
}
/**
* Returns the float value of this
* Double object.
*
* @return the double value represented by this object
* converted to type float
* @since JDK1.0
*/
public float floatValue() {
return (float)value;
}
/**
* Returns the double value of this
* Double object.
*
* @return the double value represented by this object
*/
public double doubleValue() {
return (double)value;
}
/**
* Returns a hash code for this Double object. The
* result is the exclusive OR of the two halves of the
* long integer bit representation, exactly as
* produced by the method {@link #doubleToLongBits(double)}, of
* the primitive double value represented by this
* Double object. That is, the hash code is the value
* of the expression:
*
* (int)(v^(v>>>32))
* v is defined by:
*
* long v = Double.doubleToLongBits(this.doubleValue());
* hash code value for this object.
*/
public int hashCode() {
long bits = doubleToLongBits(value);
return (int)(bits ^ (bits >>> 32));
}
/**
* Compares this object against the specified object. The result
* is true if and only if the argument is not
* null and is a Double object that
* represents a double that has the same value as the
* double represented by this object. For this
* purpose, two double values are considered to be
* the same if and only if the method {@link
* #doubleToLongBits(double)} returns the identical
* long value when applied to each.
*
* Note that in most cases, for two instances of class
* Double, d1 and d2, the
* value of d1.equals(d2) is true if and
* only if
*
* d1.doubleValue() == d2.doubleValue()
*
* also has the value true. However, there are two
* exceptions:
*
d1 and d2 both represent
* Double.NaN, then the equals method
* returns true, even though
* Double.NaN==Double.NaN has the value
* false.
* d1 represents +0.0 while
* d2 represents -0.0, or vice versa,
* the equal test has the value false,
* even though +0.0==-0.0 has the value true.
* true if the objects are the same;
* false otherwise.
* @see java.lang.Double#doubleToLongBits(double)
*/
public boolean equals(Object obj) {
return (obj instanceof Double)
&& (doubleToLongBits(((Double)obj).value) ==
doubleToLongBits(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
* 0x8000000000000000L) represents the sign of the
* floating-point number. Bits
* 62-52 (the bits that are selected by the mask
* 0x7ff0000000000000L) represent the exponent. Bits 51-0
* (the bits that are selected by the mask
* 0x000fffffffffffffL) represent the significand
* (sometimes called the mantissa) of the floating-point number.
*
* If the argument is positive infinity, the result is
* 0x7ff0000000000000L.
*
* If the argument is negative infinity, the result is
* 0xfff0000000000000L.
*
* If the argument is NaN, the result is
* 0x7ff8000000000000L.
*
* In all cases, the result is a long integer that, when
* given to the {@link #longBitsToDouble(long)} method, will produce a
* floating-point value the same as the argument to
* doubleToLongBits (except all NaN values are
* collapsed to a single "canonical" NaN value).
*
* @param value a double precision floating-point number.
* @return the bits that represent the floating-point number.
*/
public static native long doubleToLongBits(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
* 0x8000000000000000L) represents the sign of the
* floating-point number. Bits
* 62-52 (the bits that are selected by the mask
* 0x7ff0000000000000L) represent the exponent. Bits 51-0
* (the bits that are selected by the mask
* 0x000fffffffffffffL) represent the significand
* (sometimes called the mantissa) of the floating-point number.
*
* If the argument is positive infinity, the result is
* 0x7ff0000000000000L.
*
* If the argument is negative infinity, the result is
* 0xfff0000000000000L.
*
* If the argument is NaN, the result is the long
* integer representing the actual NaN value. Unlike the
* doubleToLongBits method,
* doubleToRawLongBits does not collapse all the bit
* patterns encoding a NaN to a single "canonical" NaN
* value.
*
* In all cases, the result is a long integer that,
* when given to the {@link #longBitsToDouble(long)} method, will
* produce a floating-point value the same as the argument to
* doubleToRawLongBits.
*
* @param value a double precision floating-point number.
* @return the bits that represent the floating-point number.
*/
public static native long doubleToRawLongBits(double value);
/**
* Returns the 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 0x7ff0000000000000L, the result
* is positive infinity.
*
* If the argument is 0xfff0000000000000L, the result
* is negative infinity.
*
* If the argument is any value in the range
* 0x7ff0000000000001L through
* 0x7fffffffffffffffL or in the range
* 0xfff0000000000001L through
* 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 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;
*
* Note that this method may not be able to return a
* double NaN with exactly same bit pattern as the
* 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 longBitsToDouble
* may not be able to return a double with a
* signaling NaN bit pattern. Consequently, for some
* long values,
* doubleToRawLongBits(longBitsToDouble(start)) may
* not equal 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 long integer.
* @return the double floating-point value with the same
* bit pattern.
*/
public static native double longBitsToDouble(long bits);
/**
* Compares two 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 (<, <=, ==, >= >)
* when applied to primitive double values:
*
Double.NaN is considered by this method
* to be equal to itself and greater than all other
* double values (including
* Double.POSITIVE_INFINITY).
* 0.0d is considered by this method to be greater
* than -0.0d.
* Double.compareTo(Object) (which
* forwards its behavior to this method) obeys the general
* contract for Comparable.compareTo, and that the
* natural order on Doubles is consistent
* with equals.
*
* @param anotherDouble the Double to be compared.
* @return the value 0 if anotherDouble is
* numerically equal to this Double; a value
* less than 0 if this Double
* is numerically less than anotherDouble;
* and a value greater than 0 if this
* Double is numerically greater than
* anotherDouble.
*
* @since 1.2
* @see Comparable#compareTo(Object)
*/
public int compareTo(Double anotherDouble) {
return Double.compare(value, anotherDouble.value);
}
/**
* Compares this Double object to another object. If
* the object is a Double, this function behaves like
* compareTo(Double). Otherwise, it throws a
* ClassCastException (as Double objects
* are comparable only to other Double objects).
*
* @param o the Object to be compared.
* @return the value 0 if the argument is a
* Double numerically equal to this
* Double; a value less than 0
* if the argument is a Double numerically
* greater than this Double; and a value
* greater than 0 if the argument is a
* Double numerically less than this
* Double.
* @exception ClassCastException if the argument is not a
* Double.
* @see java.lang.Comparable
* @since 1.2
*/
public int compareTo(Object o) {
return compareTo((Double)o);
}
/**
* Compares the two specified 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))
*
*
* @param d1 the first double to compare
* @param d2 the second double to compare
* @return the value 0 if d1 is
* numerically equal to d2; a value less than
* 0 if d1 is numerically less than
* d2; and a value greater than 0
* if d1 is numerically greater than
* d2.
* @since 1.4
*/
public static int compare(double d1, double d2) {
if (d1 < d2)
return -1; // Neither val is NaN, thisVal is smaller
if (d1 > d2)
return 1; // Neither val is NaN, thisVal is larger
long thisBits = Double.doubleToLongBits(d1);
long anotherBits = Double.doubleToLongBits(d2);
return (thisBits == anotherBits ? 0 : // Values are equal
(thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
1)); // (0.0, -0.0) or (NaN, !NaN)
}
/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = -9172774392245257468L;
}