Class java.lang.Double - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.lang.Double

java.lang.Object
   |
   +----java.lang.Number
           |
           +----java.lang.Double

public final class Double
extends Number

The 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.

MAX_VALUE: The largest positive value of type double.
MIN_VALUE: The smallest positive value of type double.
NaN: A NaN value of type double.
NEGATIVE_INFINITY: The negative infinity of type double.
POSITIVE_INFINITY: The positive infinity of type double.
TYPE: The Class object representing the primitive type double.

Double(double): Constructs a newly allocated Double object that represents the primitive double argument.
Double(String): Constructs a newly allocated Double object that represents the floating- point value of type double represented by the string.

byteValue(): Returns the value of this Double as a byte (by casting to a byte).
doubleToLongBits(double): Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "double format" bit layout.
doubleValue(): Returns the double value of this Double.
equals(Object): Compares this object against the specified object.
floatValue(): Returns the float value of this Double.
hashCode(): Returns a hashcode for this Double.
intValue(): Returns the integer value of this Double (by casting to an int).
isInfinite(): Returns true if this Double value is infinitely large in magnitude.
isInfinite(double): Returns true if the specified number is infinitely large in magnitude.
isNaN(): Returns true if this Double value is the special Not-a-Number (NaN) value.
isNaN(double): Returns true if the specified number is the special Not-a-Number (NaN) value.
longBitsToDouble(long): Returns the double-float corresponding to a given bit represention.
longValue(): Returns the long value of this Double (by casting to a long).
shortValue(): Returns the value of this Double as a short (by casting to a short).
toString(): Returns a String representation of this Double object.
toString(double): Creates a string representation of the double argument.
valueOf(String): Returns a new Double value initialized to the value represented by the specified String.

POSITIVE_INFINITY

 public static final double POSITIVE_INFINITY

The positive infinity of type double.

NEGATIVE_INFINITY

 public static final double NEGATIVE_INFINITY

The negative infinity of type double.

NaN

 public static final double NaN

A NaN value of type double.

MAX_VALUE

 public static final double MAX_VALUE

The largest positive value of type double.

MIN_VALUE

 public static final double MIN_VALUE

The smallest positive value of type double.

TYPE

 public static final Class TYPE

The Class object representing the primitive type double.

Double

 public Double(double value)

Constructs a newly allocated Double object that represents the primitive double argument.

Parameters:: value - the value to be represented by the Double.

Double

 public Double(String s) throws NumberFormatException

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.

Parameters:: s - a string to be converted to a Double.
Throws: NumberFormatException: if the string does not contain a parsable number.
See Also:: valueOf

toString

 public static String toString(double d)

Creates a string representation of the double argument.

The values NaN, NEGATIVE_INFINITY, POSITIVE_INFINITY, -0.0, and +0.0 are represented by the strings "NaN", "-Infinity", "Infinity", "-0.0", and "0.0", respectively.

If d is in the range 10^-3 <= |d| <=10⁷, then it is converted to a string in the style [-]ddd.ddd. Otherwise, it is converted to a string in the style [-]m.ddddE±xx.

There is always a minimum of one digit after the decimal point. The number of digits is the minimum needed to uniquely distinguish the argument value from adjacent values of type double.

Parameters:: d - the double to be converted.
Returns:: a string representation of the argument.

valueOf

 public static Double valueOf(String s) throws NumberFormatException

Returns a new Double value initialized to the value represented by the specified String.

Parameters:: s - the string to be parsed.
Returns:: a newly constructed Double initialized to the value represented by the string argument.
Throws: NumberFormatException: if the string does not contain a parsable number.

isNaN

 public static boolean isNaN(double v)

Returns true if the specified number is the special Not-a-Number (NaN) value.

Parameters:: v - the value to be tested.
Returns:: true if the value of the argument is NaN; false otherwise.

isInfinite

 public static boolean isInfinite(double v)

Returns true if the specified number is infinitely large in magnitude.

Parameters:: v - the value to be tested.
Returns:: true if the value of the argument is positive infinity or negative infinity; false otherwise.

isNaN

 public boolean isNaN()

Returns true if this Double value is the special Not-a-Number (NaN) value.

Returns:: true if the value represented by this object is NaN; false otherwise.

isInfinite

 public boolean isInfinite()

Returns true if this Double value is infinitely large in magnitude.

Returns:: true if the value represented by this object is positive infinity or negative infinity; false otherwise.

toString

 public String toString()

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.

Returns:: a String representation of this object.
Overrides:: toString in class Object
See Also:: toString

byteValue

 public byte byteValue()

Returns the value of this Double as a byte (by casting to a byte).

Overrides:: byteValue in class Number

shortValue

 public short shortValue()

Returns the value of this Double as a short (by casting to a short).

Overrides:: shortValue in class Number

intValue

 public int intValue()

Returns the integer value of this Double (by casting to an int).

Returns:: the double value represented by this object is converted to type int and the result of the conversion is returned.
Overrides:: intValue in class Number

longValue

 public long longValue()

Returns the long value of this Double (by casting to a long).

Returns:: the double value represented by this object is converted to type long and the result of the conversion is returned.
Overrides:: longValue in class Number

floatValue

 public float floatValue()

Returns the float value of this Double.

Returns:: the double value represented by this object is converted to type float and the result of the conversion is returned.
Overrides:: floatValue in class Number

doubleValue

 public double doubleValue()

Returns the double value of this Double.

Returns:: the double value represented by this object.
Overrides:: doubleValue in class Number

hashCode

 public int hashCode()

Returns a hashcode for this Double.

Returns:: a hash code value for this object.
Overrides:: hashCode in class Object

equals

 public boolean equals(Object obj)

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 identical bit pattern to the bit pattern of the double represented by this object.

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:

If d1 and d2 both represent Double.NaN, then the equals method returns true, even though Double.NaN==Double.NaN has the value false.
If 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.

Parameters:: obj - the object to compare with.
Returns:: true if the objects are the same; false otherwise.
Overrides:: equals in class Object

doubleToLongBits

 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.

Bit 63 represents the sign of the floating-point number. Bits 62-52 represent the exponent. Bits 51-0 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.

Parameters:: value - a double precision floating-point number.
Returns:: the bits that represent the floating-point number.

longBitsToDouble

 public static native double longBitsToDouble(long bits)

Returns the double-float corresponding to a given bit represention. The argument is considered to be a representation of a floating-point value according to the IEEE 754 floating-point "double precision" bit layout. That floating-point value is returned as the result.

If the argument is 0x7f80000000000000L, the result is positive infinity.

If the argument is 0xff80000000000000L, 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 NaN. All IEEE 754 NaN values are, in effect, lumped together by the Java language into a single value.

Parameters:: bits - any long integer.
Returns:: the double floating-point value with the same bit pattern.

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