java.lang.Objectjava.lang.Number
java.lang.Double
public final class Double
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.
Field Summary | |
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static int |
MAX_EXPONENT
Maximum exponent a finite double variable may have. |
static double |
MAX_VALUE
A constant holding the largest positive finite value of type double, (2-2 -52 )·2 1023 . |
static int |
MIN_EXPONENT
Minimum exponent a normalized double variable may have. |
static double |
MIN_NORMAL
A constant holding the smallest positive normal value of type double, 2 -1022 . |
static double |
MIN_VALUE
A constant holding the smallest positive nonzero value of type double, 2 -1074 . |
static double |
NaN
A constant holding a Not-a-Number (NaN) value of type double. |
static double |
NEGATIVE_INFINITY
A constant holding the negative infinity of type double. |
static double |
POSITIVE_INFINITY
A constant holding the positive infinity of type double. |
static int |
SIZE
The number of bits used to represent a double value. |
static Class < Double > |
TYPE
The Class instance representing the primitive type double. |
Constructor Summary | |
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Double
(double value) Constructs a newly allocated Double object that represents the primitive double argument. |
|
Double
(
String
s) Constructs a newly allocated Double object that represents the floating-point value of type double represented by the string. |
Method Summary | |
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byte |
byteValue
() Returns the value of this Double as a byte (by casting to a byte). |
static int |
compare
(double d1, double d2) Compares the two specified double values. |
int |
compareTo
(
Double
anotherDouble) Compares two Double objects numerically. |
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. |
static 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. |
double |
doubleValue
() Returns the double value of this Double object. |
boolean |
equals
(
Object
obj) Compares this object against the specified object. |
float |
floatValue
() Returns the float value of this Double object. |
int |
hashCode
() Returns a hash code for this Double object. |
int |
intValue
() Returns the value of this Double as an int (by casting to type int). |
boolean |
isInfinite
() Returns true if this Double value is infinitely large in magnitude, false otherwise. |
static boolean |
isInfinite
(double v) Returns true if the specified number is infinitely large in magnitude, false otherwise. |
boolean |
isNaN
() Returns true if this Double value is a Not-a-Number (NaN), false otherwise. |
static boolean |
isNaN
(double v) Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise. |
static double |
longBitsToDouble
(long bits) Returns the double value corresponding to a given bit representation. |
long |
longValue
() Returns the value of this Double as a long (by casting to type long). |
static double |
parseDouble
(
String
s) Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double. |
short |
shortValue
() Returns the value of this Double as a short (by casting to a short). |
static String |
toHexString
(double d) Returns a hexadecimal string representation of the double argument. |
String |
toString
() Returns a string representation of this Double object. |
static String |
toString
(double d) Returns a string representation of the double argument. |
static Double |
valueOf
(double d) Returns a Double instance representing the specified double value. |
static Double |
valueOf
(
String
s) Returns a Double object holding the double value represented by the argument string s. |
Methods inherited from class java.lang. Object |
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clone , finalize , getClass , notify , notifyAll , wait , wait , wait |
Field Detail |
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public static final double POSITIVE_INFINITY
public static final double NEGATIVE_INFINITY
public static final double NaN
public static final double MAX_VALUE
public static final double MIN_NORMAL
public static final double MIN_VALUE
public static final int MAX_EXPONENT
public static final int MIN_EXPONENT
public static final int SIZE
public static final Class<Double> TYPE
Constructor Detail |
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public Double(double value)
public Double(String s) throws NumberFormatException
Method Detail |
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public static String toString(double d)
To create localized string representations of a floating-point value, use subclasses of NumberFormat .
public static String toHexString(double d)
Floating-point Value | Hexadecimal String |
---|---|
1.0 | 0x1.0p0 |
-1.0 | -0x1.0p0 |
2.0 | 0x1.0p1 |
3.0 | 0x1.8p1 |
0.5 | 0x1.0p-1 |
0.25 | 0x1.0p-2 |
Double.MAX_VALUE | 0x1.fffffffffffffp1023 |
Minimum Normal Value | 0x1.0p-1022 |
Maximum Subnormal Value | 0x0.fffffffffffffp-1022 |
Double.MIN_VALUE | 0x0.0000000000001p-1022 |
public static Double valueOf(String s) throws NumberFormatException
If s is null, then a NullPointerException is thrown.
Leading and trailing whitespace characters in 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 s should constitute a FloatValue as described by the lexical syntax rules:
where Sign , FloatingPointLiteral , HexNumeral , HexDigits , SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of the of the Java Language Specification . If 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" 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 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.
- FloatValue:
- Sign opt NaN
- Sign opt Infinity
- Sign opt FloatingPointLiteral
- Sign opt HexFloatingPointLiteral
- SignedInteger
- HexFloatingPointLiteral :
- HexSignificand BinaryExponent FloatTypeSuffix opt
- HexSignificand:
- HexNumeral
- HexNumeral .
- 0x HexDigits opt . HexDigits
- 0X HexDigits opt . HexDigits
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
- p
- P
To interpret localized string representations of a floating-point value, use subclasses of 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.)
To avoid calling this method on
an
a
invalid string and having a 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 the Java Language Specification, 2nd // edition, section 3.10.2. // 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)
public static double parseDouble(String s) throws NumberFormatException
public static boolean isNaN(double v)
public static boolean isInfinite(double v)
public boolean isNaN()
public boolean isInfinite()
public String toString()
public byte byteValue()
public short shortValue()
public int intValue()
public long longValue()
public float floatValue()
public double doubleValue()
public int hashCode()
where v is defined by:(int)(v^(v>>>32))
long v = Double.doubleToLongBits(this.doubleValue());
public boolean equals(Object obj)
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:
public static long doubleToLongBits(double value)
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 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).
public static long doubleToRawLongBits(double value)
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 longBitsToDouble(long) method, will produce a floating-point value the same as the argument to doubleToRawLongBits.
public static double longBitsToDouble(long bits)
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:
Then the floating-point result equals the value of the mathematical expression s · m ·2 e -1075 .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.
public int compareTo(Double anotherDouble)
public static int compare(double d1, double d2)
new Double(d1).compareTo(new Double(d2))