Immutable, arbitrary-precision signed decimal numbers. A BigDecimal
consists of an arbitrary precision integer unscaled value and a
non-negative 32-bit integer scale, which represents the number of
digits to the right of the decimal point. The number represented by the
BigDecimal is (unscaledValue/10^{scale}). BigDecimal
provides operations for basic arithmetic, scale manipulation, comparison,
hashing, and format conversion.
The BigDecimal class gives its user complete control over rounding
behavior, forcing the user to explicitly specify a rounding behavior for
operations capable of discarding precision (divide and
setScale). Eight rounding modes are provided for this
purpose.
Two types of operations are provided for manipulating the scale of a
BigDecimal: scaling/rounding operations and decimal point motion
operations. Scaling/rounding operations (SetScale) return a
BigDecimal whose value is approximately (or exactly) equal to that of the
operand, but whose scale is the specified value; that is, they increase or
decrease the precision of the number with minimal effect on its value.
Decimal point motion operations (movePointLeft and
movePointRight) return a BigDecimal created from the operand by
moving the decimal point a specified distance in the specified direction;
that is, they change a number's value without affecting its precision.
For the sake of brevity and clarity, pseudo-code is used throughout the
descriptions of BigDecimal methods. The pseudo-code expression
(i + j) is shorthand for "a BigDecimal whose value is
that of the BigDecimal i plus that of the BigDecimal j."
The pseudo-code expression (i == j) is shorthand for
"true if and only if the BigDecimal i represents the same
value as the the BigDecimal j." Other pseudo-code expressions are
interpreted similarly.
Note: care should be exercised if BigDecimals are to be used as keys in a
SortedMap or elements in a SortedSet, as BigDecimal's natural
ordering is inconsistent with equals. See Comparable, SortedMap
or SortedSet for more information.
ROUND_FLOOR
Rounding mode to round towards negative infinity.
static int
ROUND_HALF_DOWN
Rounding mode to round towards "nearest neighbor" unless both
neighbors are equidistant, in which case round down.
static int
ROUND_HALF_EVEN
Rounding mode to round towards the "nearest neighbor" unless both
neighbors are equidistant, in which case, round towards the even
neighbor.
static int
ROUND_HALF_UP
Rounding mode to round towards "nearest neighbor" unless both
neighbors are equidistant, in which case round up.
static int
ROUND_UNNECESSARY
Rounding mode to assert that the requested operation has an exact
result, hence no rounding is necessary.
setScale(int scale,
int roundingMode)
Returns a BigDecimal whose scale is the specified value, and whose
unscaled value is determined by multiplying or dividing this
BigDecimal's unscaled value by the appropriate power of ten to maintain
its overall value.
int
signum()
Returns the signum function of this BigDecimal.
Rounding mode to round away from zero. Always increments the
digit prior to a non-zero discarded fraction. Note that this rounding
mode never decreases the magnitude of the calculated value.
ROUND_DOWN
public static final int ROUND_DOWN
Rounding mode to round towards zero. Never increments the digit
prior to a discarded fraction (i.e., truncates). Note that this
rounding mode never increases the magnitude of the calculated value.
ROUND_CEILING
public static final int ROUND_CEILING
Rounding mode to round towards positive infinity. If the
BigDecimal is positive, behaves as for ROUND_UP; if negative,
behaves as for ROUND_DOWN. Note that this rounding mode never
decreases the calculated value.
ROUND_FLOOR
public static final int ROUND_FLOOR
Rounding mode to round towards negative infinity. If the
BigDecimal is positive, behave as for ROUND_DOWN; if negative,
behave as for ROUND_UP. Note that this rounding mode never
increases the calculated value.
ROUND_HALF_UP
public static final int ROUND_HALF_UP
Rounding mode to round towards "nearest neighbor" unless both
neighbors are equidistant, in which case round up.
Behaves as for ROUND_UP if the discarded fraction is >= .5;
otherwise, behaves as for ROUND_DOWN. Note that this is the
rounding mode that most of us were taught in grade school.
ROUND_HALF_DOWN
public static final int ROUND_HALF_DOWN
Rounding mode to round towards "nearest neighbor" unless both
neighbors are equidistant, in which case round down.
Behaves as for ROUND_UP if the discarded fraction is > .5;
otherwise, behaves as for ROUND_DOWN.
ROUND_HALF_EVEN
public static final int ROUND_HALF_EVEN
Rounding mode to round towards the "nearest neighbor" unless both
neighbors are equidistant, in which case, round towards the even
neighbor. Behaves as for ROUND_HALF_UP if the digit to the left of the
discarded fraction is odd; behaves as for ROUND_HALF_DOWN if it's even.
Note that this is the rounding mode that minimizes cumulative error
when applied repeatedly over a sequence of calculations.
ROUND_UNNECESSARY
public static final int ROUND_UNNECESSARY
Rounding mode to assert that the requested operation has an exact
result, hence no rounding is necessary. If this rounding mode is
specified on an operation that yields an inexact result, an
ArithmeticException is thrown.
Translates the String representation of a BigDecmal into a BigDecimal.
The String representation consists of an optional minus sign followed
by a sequence of zero or more decimal digits, optionally followed by a
fraction. The fraction consists of of a decimal point followed by zero
or more decimal digits. The string must contain at least one digit in
the integer or fractional part. The scale of the resulting BigDecimal
will be the number of digits to the right of the decimal point in the
string, or 0 if the string contains no decimal point. The
character-to-digit mapping is provided by Character.digit. The String
may not contain any extraneous characters (whitespace, for example).
Translates a double into a BigDecimal. The scale of the BigDecimal
is the smallest value such that (10^{scale} * val)
is an integer.
Note: the results of this constructor can be somewhat unpredictable.
One might assume that new BigDecimal(.1) is exactly equal
to .1, but it is actually equal
to .1000000000000000055511151231257827021181583404541015625.
This is so because .1 cannot be represented exactly as a double
(or, for that matter, as a binary fraction of any finite length).
Thus, the long value that is being passed in to the constructor is
not exactly equal to .1, appearances nonwithstanding.
The (String) constructor, on the other hand, is perfectly predictable:
new BigDecimal(".1") is exactly equal to .1, as one
would expect. Therefore, it is generally recommended that the (String)
constructor be used in preference to this one.
Parameters:
val - double value to be converted to BigDecimal.
Throws:
NumberFormatException - val is equal to
Double.NEGATIVE_INFINITY,
Double.POSITIVE_INFINITY, or Double.NaN.
public static BigDecimalvalueOf(long unscaledVal,
int scale)
Translates a long unscaled value and an int scale into a BigDecimal.
This "static factory method" is provided in preference to a
(long, int) constructor because it allows for reuse of frequently used
BigDecimals.
Parameters:
unscaledVal - unscaled value of the BigDecimal.
scale - scale of the BigDecimal.
Returns:
a BigDecimal whose value is
(unscaledVal/10^{scale}).
Translates a long value into a BigDecimal with a scale of zero.
This "static factory method" is provided in preference to a
(long) constructor because it allows for reuse of frequently
used BigDecimals.
Returns a BigDecimal whose value is (this / val), and whose
scale is as specified. If rounding must be performed to generate a
result with the specified scale, the specified rounding mode is
applied.
Parameters:
val - value by which this BigDecimal is to be divided.
scale - scale of the BigDecimal quotient to be returned.
roundingMode - rounding mode to apply.
Returns:
this / val
Throws:
ArithmeticException - val is zero, scale is
negative, or roundingMode==ROUND_UNNECESSARY and
the specified scale is insufficient to represent the result
of the division exactly.
Returns a BigDecimal whose value is (this / val), and whose
scale is this.scale(). If rounding must be performed to
generate a result with the given scale, the specified rounding mode is
applied.
Parameters:
val - value by which this BigDecimal is to be divided.
roundingMode - rounding mode to apply.
Returns:
this / val
Throws:
ArithmeticException - val==0, or
roundingMode==ROUND_UNNECESSARY and
this.scale() is insufficient to represent the result
of the division exactly.
Returns a BigInteger whose value is the unscaled value of this
BigDecimal. (Computes (this * 10^{this.scale()}).)
Returns:
the unscaled value of this BigDecimal.
Since:
JDK1.2
setScale
public BigDecimalsetScale(int scale,
int roundingMode)
Returns a BigDecimal whose scale is the specified value, and whose
unscaled value is determined by multiplying or dividing this
BigDecimal's unscaled value by the appropriate power of ten to maintain
its overall value. If the scale is reduced by the operation, the
unscaled value must be divided (rather than multiplied), and the value
may be changed; in this case, the specified rounding mode is applied to
the division.
Parameters:
scale - scale of the BigDecimal value to be returned.
Returns:
a BigDecimal whose scale is the specified value, and whose
unscaled value is determined by multiplying or dividing this
BigDecimal's unscaled value by the appropriate power of ten to
maintain its overall value.
Throws:
ArithmeticException - scale is negative, or
roundingMode==ROUND_UNNECESSARY and the specified
scaling operation would require rounding.
Returns a BigDecimal whose scale is the specified value, and whose
value is numerically equal to this BigDecimal's. Throws an
ArithmeticException if this is not possible. This call is typically
used to increase the scale, in which case it is guaranteed that there
exists a BigDecimal of the specified scale and the correct value. The
call can also be used to reduce the scale if the caller knows that the
BigDecimal has sufficiently many zeros at the end of its fractional
part (i.e., factors of ten in its integer value) to allow for the
rescaling without loss of precision.
Note that this call returns the same result as the two argument version
of setScale, but saves the caller the trouble of specifying a rounding
mode in cases where it is irrelevant.
Parameters:
scale - scale of the BigDecimal value to be returned.
Returns:
a BigDecimal whose scale is the specified value, and whose
unscaled value is determined by multiplying or dividing this
BigDecimal's unscaled value by the appropriate power of ten to
maintain its overall value.
Throws:
ArithmeticException - scale is negative, or
the specified scaling operation would require rounding.
Returns a BigDecimal which is equivalent to this one with the decimal
point moved n places to the left. If n is non-negative, the call merely
adds n to the scale. If n is negative, the call is equivalent to
movePointRight(-n). (The BigDecimal returned by this call has value
(this * 10^{-n}) and scale
max(this.scale()+n, 0).)
Parameters:
n - number of places to move the decimal point to the left.
Returns:
a BigDecimal which is equivalent to this one with the decimal
point moved n places to the left.
Moves the decimal point the specified number of places to the right.
If this BigDecimal's scale is >= n, the call merely
subtracts n from the scale; otherwise, it sets the scale to
zero, and multiplies the integer value by
10^{(n - this.scale)}. If n
is negative, the call is equivalent to movePointLeft(-n). (The
BigDecimal returned by this call has value
(this * 10^{n}) and scale
max(this.scale()-n, 0).)
Parameters:
n - number of places to move the decimal point to the right.
Returns:
a BigDecimal which is equivalent to this one with the decimal
point moved n places to the right.
Compares this BigDecimal with the specified BigDecimal. Two
BigDecimals that are equal in value but have a different scale (like
2.0 and 2.00) are considered equal by this method. This method is
provided in preference to individual methods for each of the six
boolean comparison operators (<, ==, >, >=, !=, <=). The
suggested idiom for performing these comparisons is:
(x.compareTo(y) <op> 0),
where <op> is one of the six comparison operators.
Parameters:
val - BigDecimal to which this BigDecimal is to be compared.
Returns:
-1, 0 or 1 as this BigDecimal is numerically less than, equal
to, or greater than val.
Compares this BigDecimal with the specified Object. If the Object is a
BigDecimal, this method behaves like compareTo(BigDecimal).
Otherwise, it throws a ClassCastException (as BigDecimals are
comparable only to other BigDecimals).
Compares this BigDecimal with the specified Object for equality.
Unlike compareTo, this method considers two BigDecimals equal only
if they are equal in value and scale (thus 2.0 is not equal to 2.00
when compared by this method).
Returns the hash code for this BigDecimal. Note that two BigDecimals
that are numerically equal but differ in scale (like 2.0 and 2.00)
will generally not have the same hash code.
Returns the string representation of this BigDecimal. The digit-to-
character mapping provided by Character.forDigit is used.
A leading minus sign is used to indicate sign, and the number of digits
to the right of the decimal point is used to indicate scale. (This
representation is compatible with the (String) constructor.)
Converts this BigDecimal to a BigInteger. Standard narrowing
primitive conversion as defined in The Java Language
Specification: any fractional part of this BigDecimal will be
discarded.
Returns:
this BigDecimal converted to a BigInteger.
intValue
public int intValue()
Converts this BigDecimal to an int. Standard narrowing primitive
conversion as defined in The Java Language Specification:
any fractional part of this BigDecimal will be discarded, and if the
resulting "BigInteger" is too big to fit in an int, only the low-order
32 bits are returned.
Converts this BigDecimal to a long. Standard narrowing primitive
conversion as defined in The Java Language Specification:
any fractional part of this BigDecimal will be discarded, and if the
resulting "BigInteger" is too big to fit in a long, only the low-order
64 bits are returned.
Converts this BigDecimal to a float. Similar to the double-to-float
narrowing primitive conversion defined in The Java Language
Specification: if this BigDecimal has too great a magnitude to
represent as a float, it will be converted to
FLOAT.NEGATIVE_INFINITY or FLOAT.POSITIVE_INFINITY
as appropriate.
Converts this BigDecimal to a double. Similar to the double-to-float
narrowing primitive conversion defined in The Java Language
Specification: if this BigDecimal has too great a magnitude to
represent as a double, it will be converted to
DOUBLE.NEGATIVE_INFINITY or DOUBLE.POSITIVE_INFINITY
as appropriate.
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