Class Double

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).

A constant holding the smallest positive nonzero value of type double, 2^-1074. It is equal to the value returned by Double.longBitsToDouble(0x1L).

A constant holding a Not-a-Number (NaN) value of type double. It is equivalent to the value returned by Double.longBitsToDouble(0x7ff8000000000000L).

A constant holding the negative infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0xfff0000000000000L).

A constant holding the positive infinity of type double. It is equal to the value returned by Double.longBitsToDouble(0x7ff0000000000000L).

The Class instance representing the primitive type double.

Since: JDK1.1

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

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

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

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

Returns: the double value represented by this object converted to type byte

Since: JDK1.1

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))
 

Parameters: d1 the first double to compare d2 the second double to compare

Returns: 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

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.

This ensures that 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.

Parameters: anotherDouble the Double to be compared.

Returns: 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 Also: compareTo

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 Double 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).

Parameters: value a double precision floating-point number.

Returns: the bits that represent the floating-point number.

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 Double method, will produce a floating-point value the same as the argument to doubleToRawLongBits.

Parameters: value a double precision floating-point number.

Returns: the bits that represent the floating-point number.

Returns the double value of this Double object.

Returns: the double value represented by this object

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 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:

• 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.

This definition allows hash tables to operate properly.

Parameters: obj the object to compare with.

Returns: true if the objects are the same; false otherwise.

See Also: Double

Returns the float value of this Double object.

Returns: the double value represented by this object converted to type float

Since: JDK1.0

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 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))
 

where v is defined by:

 long v = Double.doubleToLongBits(this.doubleValue());
 

Returns: a hash code value for this object.

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

Returns: the double value represented by this object converted to type int

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

Parameters: v the value to be tested.

Returns: true if the value of the argument is positive infinity or negative infinity; false otherwise.

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

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

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

Parameters: v the value to be tested.

Returns: true if the value of the argument is NaN; false otherwise.

Returns true if this Double value is a Not-a-Number (NaN), false otherwise.

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

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;
 

Then the floating-point result equals the value of the mathematical expression s·m·2^e-1075.

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.

Parameters: bits any long integer.

Returns: the double floating-point value with the same bit pattern.

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

Returns: the double value represented by this object converted to type long

Returns a new double initialized to the value represented by the specified String, as performed by the valueOf method of class Double.

Parameters: s the string to be parsed.

Returns: the double value represented by the string argument.

Throws: NumberFormatException if the string does not contain a parsable double.

Since: 1.2

See Also: valueOf

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

Returns: the double value represented by this object converted to type short

Since: JDK1.1

Returns a string representation of the double argument. All characters mentioned below are ASCII characters.

• If the argument is NaN, the result is the string "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 '-' ('\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 "Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity".
  • If m is zero, it is represented by the characters "0.0"; thus, negative zero produces the result "-0.0" and positive zero produces the result "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 '.' ('\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 10ⁿ <= m < 10ⁿ⁺¹; then let a be the mathematically exact quotient of m and 10ⁿ so that 1 <= a < 10. The magnitude is then represented as the integer part of a, as a single decimal digit, followed by '.' ('\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 Integer.

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 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 java.text.NumberFormat.

Parameters: d the double to be converted.

Returns: a string representation of the argument.

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.

See Also: Double

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. Whitespace is removed as if by the String 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:

FloatValue:

Sign_opt NaN

Sign_opt Infinity

Sign_opt FloatingPointLiteral

SignedInteger

where Sign, FloatingPointLiteral, and SignedInteger are as defined in §3.10.2 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"; 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 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.)

To avoid calling this method on 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}+)";
	// 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 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+")?))"+
	     "[fFdD]?))" +
	     "[\\x00-\\x20]*");// Optional trailing "whitespace"
	    
	Pattern fpPattern = Pattern.compile(fpRegex);
	if (fpPattern.match(myString))
	    Double.valueOf(myString); // Will not throw NumberFormatException
	else {
	    // Perform suitable alternative action
	}
 

Parameters: s the string to be parsed.

Returns: a Double object holding the value represented by the String argument.

Throws: NumberFormatException if the string does not contain a parsable number.

Returns a Double instance representing the specified double value. If a new Double instance is not required, this method should generally be used in preference to the constructor Double, as this method is likely to to yield significantly better space and time performance by cacheing frequently requested values.

Parameters: d a double value.

Returns: a Double instance representing d.

Since: 1.5