程序包 java.math

类 BigDecimal

java.lang.Object

java.lang.Number

java.math.BigDecimal

所有已实现的接口:

Serializable, Comparable<BigDecimal>

public class BigDecimal
extends Number
implements Comparable<BigDecimal>

Immutable, arbitrary-precision signed decimal numbers. A BigDecimal consists of an arbitrary precision integer unscaled value and a 32-bit integer scale. If zero or positive, the scale is the number of digits to the right of the decimal point. If negative, the unscaled value of the number is multiplied by ten to the power of the negation of the scale. The value of the number represented by the BigDecimal is therefore (unscaledValue × 10^-scale).

The BigDecimal class provides operations for arithmetic, scale manipulation, rounding, comparison, hashing, and format conversion. The toString() method provides a canonical representation of a BigDecimal.

The BigDecimal class gives its user complete control over rounding behavior. If no rounding mode is specified and the exact result cannot be represented, an exception is thrown; otherwise, calculations can be carried out to a chosen precision and rounding mode by supplying an appropriate MathContext object to the operation. In either case, eight rounding modes are provided for the control of rounding. Using the integer fields in this class (such as ROUND_HALF_UP) to represent rounding mode is largely obsolete; the enumeration values of the RoundingMode enum, (such as RoundingMode#HALF_UP) should be used instead.

When a MathContext object is supplied with a precision setting of 0 (for example, MathContext#UNLIMITED), arithmetic operations are exact, as are the arithmetic methods which take no MathContext object. (This is the only behavior that was supported in releases prior to 5.) As a corollary of computing the exact result, the rounding mode setting of a MathContext object with a precision setting of 0 is not used and thus irrelevant. In the case of divide, the exact quotient could have an infinitely long decimal expansion; for example, 1 divided by 3. If the quotient has a nonterminating decimal expansion and the operation is specified to return an exact result, an ArithmeticException is thrown. Otherwise, the exact result of the division is returned, as done for other operations.

When the precision setting is not 0, the rules of BigDecimal arithmetic are broadly compatible with selected modes of operation of the arithmetic defined in ANSI X3.274-1996 and ANSI X3.274-1996/AM 1-2000 (section 7.4). Unlike those standards, BigDecimal includes many rounding modes, which were mandatory for division in BigDecimal releases prior to 5. Any conflicts between these ANSI standards and the BigDecimal specification are resolved in favor of BigDecimal.

Since the same numerical value can have different representations (with different scales), the rules of arithmetic and rounding must specify both the numerical result and the scale used in the result's representation.

In general the rounding modes and precision setting determine how operations return results with a limited number of digits when the exact result has more digits (perhaps infinitely many in the case of division) than the number of digits returned. First, the total number of digits to return is specified by the MathContext's precision setting; this determines the result's precision. The digit count starts from the leftmost nonzero digit of the exact result. The rounding mode determines how any discarded trailing digits affect the returned result.

For all arithmetic operators , the operation is carried out as though an exact intermediate result were first calculated and then rounded to the number of digits specified by the precision setting (if necessary), using the selected rounding mode. If the exact result is not returned, some digit positions of the exact result are discarded. When rounding increases the magnitude of the returned result, it is possible for a new digit position to be created by a carry propagating to a leading "9" digit. For example, rounding the value 999.9 to three digits rounding up would be numerically equal to one thousand, represented as 100×10¹. In such cases, the new "1" is the leading digit position of the returned result.

Besides a logical exact result, each arithmetic operation has a preferred scale for representing a result. The preferred scale for each operation is listed in the table below.

Preferred Scales for Results of Arithmetic Operations

Operation	Preferred Scale of Result
Add	max(addend.scale(), augend.scale())
Subtract	max(minuend.scale(), subtrahend.scale())
Multiply	multiplier.scale() + multiplicand.scale()
Divide	dividend.scale() - divisor.scale()

These scales are the ones used by the methods which return exact arithmetic results; except that an exact divide may have to use a larger scale since the exact result may have more digits. For example, 1/32 is 0.03125.

Before rounding, the scale of the logical exact intermediate result is the preferred scale for that operation. If the exact numerical result cannot be represented in precision digits, rounding selects the set of digits to return and the scale of the result is reduced from the scale of the intermediate result to the least scale which can represent the precision digits actually returned. If the exact result can be represented with at most precision digits, the representation of the result with the scale closest to the preferred scale is returned. In particular, an exactly representable quotient may be represented in fewer than precision digits by removing trailing zeros and decreasing the scale. For example, rounding to three digits using the RoundingMode#FLOOR rounding mode,
19/100 = 0.19 // integer=19, scale=2
but
21/110 = 0.190 // integer=190, scale=3

Note that for add, subtract, and multiply, the reduction in scale will equal the number of digit positions of the exact result which are discarded. If the rounding causes a carry propagation to create a new high-order digit position, an additional digit of the result is discarded than when no new digit position is created.

Other methods may have slightly different rounding semantics. For example, the result of the pow method using the specified algorithm can occasionally differ from the rounded mathematical result by more than one unit in the last place, one ulp.

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 and round) return a BigDecimal whose value is approximately (or exactly) equal to that of the operand, but whose scale or precision is the specified value; that is, they increase or decrease the precision of the stored 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.

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 added to 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 BigDecimal j." Other pseudo-code expressions are interpreted similarly. Square brackets are used to represent the particular BigInteger and scale pair defining a BigDecimal value; for example [19, 2] is the BigDecimal numerically equal to 0.19 having a scale of 2.

Note: care should be exercised if BigDecimal objects are used as keys in a SortedMap or elements in a SortedSet since BigDecimal's natural ordering is inconsistent with equals. See Comparable, SortedMap or SortedSet for more information.

All methods and constructors for this class throw NullPointerException when passed a null object reference for any input parameter.

另请参阅:

BigInteger, MathContext, RoundingMode, SortedMap, SortedSet, 序列化表格

字段概要

字段

限定符和类型	字段	说明
static BigDecimal	ONE	The value 1, with a scale of 0.
static int	ROUND_CEILING	Rounding mode to round towards positive infinity.
static int	ROUND_DOWN	Rounding mode to round towards zero.
static int	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.
static int	ROUND_UP	Rounding mode to round away from zero.
static BigDecimal	TEN	The value 10, with a scale of 0.
static BigDecimal	ZERO	The value 0, with a scale of 0.

构造器概要

构造器

构造器	说明
BigDecimal(char[] in)	Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor.
BigDecimal(char[] in, int offset, int len)	Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor, while allowing a sub-array to be specified.
BigDecimal(char[] in, int offset, int len, MathContext mc)	Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor, while allowing a sub-array to be specified and with rounding according to the context settings.
BigDecimal(char[] in, MathContext mc)	Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor and with rounding according to the context settings.
BigDecimal(double val)	Translates a double into a BigDecimal which is the exact decimal representation of the double's binary floating-point value.
BigDecimal(double val, MathContext mc)	Translates a double into a BigDecimal, with rounding according to the context settings.
BigDecimal(int val)	Translates an int into a BigDecimal.
BigDecimal(int val, MathContext mc)	Translates an int into a BigDecimal, with rounding according to the context settings.
BigDecimal(long val)	Translates a long into a BigDecimal.
BigDecimal(long val, MathContext mc)	Translates a long into a BigDecimal, with rounding according to the context settings.
BigDecimal(String val)	Translates the string representation of a BigDecimal into a BigDecimal.
BigDecimal(String val, MathContext mc)	Translates the string representation of a BigDecimal into a BigDecimal, accepting the same strings as the BigDecimal(java.lang.String) constructor, with rounding according to the context settings.
BigDecimal(BigInteger val)	Translates a BigInteger into a BigDecimal.
BigDecimal(BigInteger unscaledVal, int scale)	Translates a BigInteger unscaled value and an int scale into a BigDecimal.
BigDecimal(BigInteger unscaledVal, int scale, MathContext mc)	Translates a BigInteger unscaled value and an int scale into a BigDecimal, with rounding according to the context settings.
BigDecimal(BigInteger val, MathContext mc)	Translates a BigInteger into a BigDecimal rounding according to the context settings.

方法概要

限定符和类型	方法	说明
BigDecimal	abs()	Returns a BigDecimal whose value is the absolute value of this BigDecimal, and whose scale is this.scale().
BigDecimal	abs(MathContext mc)	Returns a BigDecimal whose value is the absolute value of this BigDecimal, with rounding according to the context settings.
BigDecimal	add(BigDecimal augend)	Returns a BigDecimal whose value is (this + augend), and whose scale is max(this.scale(), augend.scale()).
BigDecimal	add(BigDecimal augend, MathContext mc)	Returns a BigDecimal whose value is (this + augend), with rounding according to the context settings.
byte	byteValueExact()	Converts this BigDecimal to a byte, checking for lost information.
int	compareTo(BigDecimal val)	Compares this BigDecimal with the specified BigDecimal.
BigDecimal	divide(BigDecimal divisor)	Returns a BigDecimal whose value is (this / divisor), and whose preferred scale is (this.scale() - divisor.scale()); if the exact quotient cannot be represented (because it has a non-terminating decimal expansion) an ArithmeticException is thrown.
BigDecimal	divide(BigDecimal divisor, int roundingMode)	Returns a BigDecimal whose value is (this / divisor), and whose scale is this.scale().
BigDecimal	divide(BigDecimal divisor, int scale, int roundingMode)	Returns a BigDecimal whose value is (this / divisor), and whose scale is as specified.
BigDecimal	divide(BigDecimal divisor, int scale, RoundingMode roundingMode)	Returns a BigDecimal whose value is (this / divisor), and whose scale is as specified.
BigDecimal	divide(BigDecimal divisor, MathContext mc)	Returns a BigDecimal whose value is (this / divisor), with rounding according to the context settings.
BigDecimal	divide(BigDecimal divisor, RoundingMode roundingMode)	Returns a BigDecimal whose value is (this / divisor), and whose scale is this.scale().
BigDecimal[]	divideAndRemainder(BigDecimal divisor)	Returns a two-element BigDecimal array containing the result of divideToIntegralValue followed by the result of remainder on the two operands.
BigDecimal[]	divideAndRemainder(BigDecimal divisor, MathContext mc)	Returns a two-element BigDecimal array containing the result of divideToIntegralValue followed by the result of remainder on the two operands calculated with rounding according to the context settings.
BigDecimal	divideToIntegralValue(BigDecimal divisor)	Returns a BigDecimal whose value is the integer part of the quotient (this / divisor) rounded down.
BigDecimal	divideToIntegralValue(BigDecimal divisor, MathContext mc)	Returns a BigDecimal whose value is the integer part of (this / divisor).
double	doubleValue()	Converts this BigDecimal to a double.
boolean	equals(Object x)	Compares this BigDecimal with the specified Object for equality.
float	floatValue()	Converts this BigDecimal to a float.
int	hashCode()	Returns the hash code for this BigDecimal.
int	intValue()	Converts this BigDecimal to an int.
int	intValueExact()	Converts this BigDecimal to an int, checking for lost information.
long	longValue()	Converts this BigDecimal to a long.
long	longValueExact()	Converts this BigDecimal to a long, checking for lost information.
BigDecimal	max(BigDecimal val)	Returns the maximum of this BigDecimal and val.
BigDecimal	min(BigDecimal val)	Returns the minimum of this BigDecimal and val.
BigDecimal	movePointLeft(int n)	Returns a BigDecimal which is equivalent to this one with the decimal point moved n places to the left.
BigDecimal	movePointRight(int n)	Returns a BigDecimal which is equivalent to this one with the decimal point moved n places to the right.
BigDecimal	multiply(BigDecimal multiplicand)	Returns a BigDecimal whose value is (this × multiplicand), and whose scale is (this.scale() + multiplicand.scale()).
BigDecimal	multiply(BigDecimal multiplicand, MathContext mc)	Returns a BigDecimal whose value is (this × multiplicand), with rounding according to the context settings.
BigDecimal	negate()	Returns a BigDecimal whose value is (-this), and whose scale is this.scale().
BigDecimal	negate(MathContext mc)	Returns a BigDecimal whose value is (-this), with rounding according to the context settings.
BigDecimal	plus()	Returns a BigDecimal whose value is (+this), and whose scale is this.scale().
BigDecimal	plus(MathContext mc)	Returns a BigDecimal whose value is (+this), with rounding according to the context settings.
BigDecimal	pow(int n)	Returns a BigDecimal whose value is (thisn), The power is computed exactly, to unlimited precision.
BigDecimal	pow(int n, MathContext mc)	Returns a BigDecimal whose value is (thisn).
int	precision()	Returns the precision of this BigDecimal.
BigDecimal	remainder(BigDecimal divisor)	Returns a BigDecimal whose value is (this % divisor).
BigDecimal	remainder(BigDecimal divisor, MathContext mc)	Returns a BigDecimal whose value is (this % divisor), with rounding according to the context settings.
BigDecimal	round(MathContext mc)	Returns a BigDecimal rounded according to the MathContext settings.
int	scale()	Returns the scale of this BigDecimal.
BigDecimal	scaleByPowerOfTen(int n)	Returns a BigDecimal whose numerical value is equal to (this * 10n).
BigDecimal	setScale(int newScale)	Returns a BigDecimal whose scale is the specified value, and whose value is numerically equal to this BigDecimal's.
BigDecimal	setScale(int newScale, 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.
BigDecimal	setScale(int newScale, RoundingMode 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.
short	shortValueExact()	Converts this BigDecimal to a short, checking for lost information.
int	signum()	Returns the signum function of this BigDecimal.
BigDecimal	stripTrailingZeros()	Returns a BigDecimal which is numerically equal to this one but with any trailing zeros removed from the representation.
BigDecimal	subtract(BigDecimal subtrahend)	Returns a BigDecimal whose value is (this - subtrahend), and whose scale is max(this.scale(), subtrahend.scale()).
BigDecimal	subtract(BigDecimal subtrahend, MathContext mc)	Returns a BigDecimal whose value is (this - subtrahend), with rounding according to the context settings.
BigInteger	toBigInteger()	Converts this BigDecimal to a BigInteger.
BigInteger	toBigIntegerExact()	Converts this BigDecimal to a BigInteger, checking for lost information.
String	toEngineeringString()	Returns a string representation of this BigDecimal, using engineering notation if an exponent is needed.
String	toPlainString()	Returns a string representation of this BigDecimal without an exponent field.
String	toString()	Returns the string representation of this BigDecimal, using scientific notation if an exponent is needed.
BigDecimal	ulp()	Returns the size of an ulp, a unit in the last place, of this BigDecimal.
BigInteger	unscaledValue()	Returns a BigInteger whose value is the unscaled value of this BigDecimal.
static BigDecimal	valueOf(double val)	Translates a double into a BigDecimal, using the double's canonical string representation provided by the Double#toString(double) method.
static BigDecimal	valueOf(long val)	Translates a long value into a BigDecimal with a scale of zero.
static BigDecimal	valueOf(long unscaledVal, int scale)	Translates a long unscaled value and an int scale into a BigDecimal.

从类继承的方法 java.lang.Number

byteValue, shortValue

从类继承的方法 java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

字段详细资料

ONE

public static final BigDecimal ONE

The value 1, with a scale of 0.

从以下版本开始:

1.5

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.

另请参阅:

常量字段值

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.

另请参阅:

常量字段值

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.

另请参阅:

常量字段值

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 > 0.5; otherwise, behaves as for ROUND_DOWN.

另请参阅:

常量字段值

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.

另请参阅:

常量字段值

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 ≥ 0.5; otherwise, behaves as for ROUND_DOWN. Note that this is the rounding mode that most of us were taught in grade school.

另请参阅:

常量字段值

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.

另请参阅:

常量字段值

ROUND_UP

public static final int ROUND_UP

Rounding mode to round away from zero. Always increments the digit prior to a nonzero discarded fraction. Note that this rounding mode never decreases the magnitude of the calculated value.

另请参阅:

常量字段值

TEN

public static final BigDecimal TEN

The value 10, with a scale of 0.

从以下版本开始:

1.5

ZERO

public static final BigDecimal ZERO

The value 0, with a scale of 0.

从以下版本开始:

1.5

构造器详细资料

BigDecimal

public BigDecimal(char[] in,
                  int offset,
                  int len)

Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor, while allowing a sub-array to be specified.

Note that if the sequence of characters is already available within a character array, using this constructor is faster than converting the char array to string and using the BigDecimal(String) constructor .

参数:

in - char array that is the source of characters.

offset - first character in the array to inspect.

len - number of characters to consider.

抛出:

NumberFormatException - if in is not a valid representation of a BigDecimal or the defined subarray is not wholly within in.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(char[] in,
                  int offset,
                  int len,
                  MathContext mc)

Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor, while allowing a sub-array to be specified and with rounding according to the context settings.

Note that if the sequence of characters is already available within a character array, using this constructor is faster than converting the char array to string and using the BigDecimal(String) constructor .

参数:

in - char array that is the source of characters.

offset - first character in the array to inspect.

len - number of characters to consider..

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

NumberFormatException - if in is not a valid representation of a BigDecimal or the defined subarray is not wholly within in.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(char[] in)

Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor.

Note that if the sequence of characters is already available as a character array, using this constructor is faster than converting the char array to string and using the BigDecimal(String) constructor .

参数:

in - char array that is the source of characters.

抛出:

NumberFormatException - if in is not a valid representation of a BigDecimal.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(char[] in,
                  MathContext mc)

Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(java.lang.String) constructor and with rounding according to the context settings.

Note that if the sequence of characters is already available as a character array, using this constructor is faster than converting the char array to string and using the BigDecimal(String) constructor .

参数:

in - char array that is the source of characters.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

NumberFormatException - if in is not a valid representation of a BigDecimal.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(String val)

Translates the string representation of a BigDecimal into a BigDecimal. The string representation consists of an optional sign, '+' ( '\u002B') or '-' ('\u002D'), followed by a sequence of zero or more decimal digits ("the integer"), optionally followed by a fraction, optionally followed by an exponent.

The fraction consists of a decimal point followed by zero or more decimal digits. The string must contain at least one digit in either the integer or the fraction. The number formed by the sign, the integer and the fraction is referred to as the significand.

The exponent consists of the character 'e' ('\u0065') or 'E' ('\u0045') followed by one or more decimal digits. The value of the exponent must lie between -Integer#MAX_VALUE (Integer#MIN_VALUE+1) and Integer#MAX_VALUE, inclusive.

More formally, the strings this constructor accepts are described by the following grammar:

BigDecimalString:

Sign_opt Significand Exponent_opt

Sign:

+

-

Significand:

IntegerPart . FractionPart_opt

. FractionPart

IntegerPart

IntegerPart:

Digits

FractionPart:

Digits

Exponent:

ExponentIndicator SignedInteger

ExponentIndicator:

e

E

SignedInteger:

Sign_opt Digits

Digits:

Digit

Digits Digit

Digit:

any character for which Character#isDigit returns true, including 0, 1, 2 ...

The scale of the returned BigDecimal will be the number of digits in the fraction, or zero if the string contains no decimal point, subject to adjustment for any exponent; if the string contains an exponent, the exponent is subtracted from the scale. The value of the resulting scale must lie between Integer.MIN_VALUE and Integer.MAX_VALUE, inclusive.

The character-to-digit mapping is provided by Character.digit(char, int) set to convert to radix 10. The String may not contain any extraneous characters (whitespace, for example).

Examples:
The value of the returned BigDecimal is equal to significand × 10 ^exponent. For each string on the left, the resulting representation [BigInteger, scale] is shown on the right.

 "0"            [0,0]
 "0.00"         [0,2]
 "123"          [123,0]
 "-123"         [-123,0]
 "1.23E3"       [123,-1]
 "1.23E+3"      [123,-1]
 "12.3E+7"      [123,-6]
 "12.0"         [120,1]
 "12.3"         [123,1]
 "0.00123"      [123,5]
 "-1.23E-12"    [-123,14]
 "1234.5E-4"    [12345,5]
 "0E+7"         [0,-7]
 "-0"           [0,0]
 

Note: For values other than float and double NaN and ±Infinity, this constructor is compatible with the values returned by Float#toString and Double#toString. This is generally the preferred way to convert a float or double into a BigDecimal, as it doesn't suffer from the unpredictability of the BigDecimal(double) constructor.

参数:

val - String representation of BigDecimal.

抛出:

NumberFormatException - if val is not a valid representation of a BigDecimal.

BigDecimal

public BigDecimal(String val,
                  MathContext mc)

Translates the string representation of a BigDecimal into a BigDecimal, accepting the same strings as the BigDecimal(java.lang.String) constructor, with rounding according to the context settings.

参数:

val - string representation of a BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

NumberFormatException - if val is not a valid representation of a BigDecimal.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(double val)

Translates a double into a BigDecimal which is the exact decimal representation of the double's binary floating-point value. The scale of the returned BigDecimal is the smallest value such that (10^scale × val) is an integer.

Notes:

1. The results of this constructor can be somewhat unpredictable. One might assume that writing new BigDecimal(0.1) in Java creates a BigDecimal which is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625. This is because 0.1 cannot be represented exactly as a double (or, for that matter, as a binary fraction of any finite length). Thus, the value that is being passed in to the constructor is not exactly equal to 0.1, appearances notwithstanding.
2. The String constructor, on the other hand, is perfectly predictable: writing new BigDecimal("0.1") creates a BigDecimal which is exactly equal to 0.1, as one would expect. Therefore, it is generally recommended that the Stringconstructor be used in preference to this one.
3. When a double must be used as a source for a BigDecimal, note that this constructor provides an exact conversion; it does not give the same result as converting the double to a String using the Double#toString(double) method and then using the BigDecimal(java.lang.String) constructor. To get that result, use the static valueOf(double) method.

参数:

val - double value to be converted to BigDecimal.

抛出:

NumberFormatException - if val is infinite or NaN.

BigDecimal

public BigDecimal(double val,
                  MathContext mc)

Translates a double into a BigDecimal, with rounding according to the context settings. The scale of the BigDecimal is the smallest value such that (10^scale × val) is an integer.

The results of this constructor can be somewhat unpredictable and its use is generally not recommended; see the notes under the BigDecimal(double) constructor.

参数:

val - double value to be converted to BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the RoundingMode is UNNECESSARY.

NumberFormatException - if val is infinite or NaN.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(BigInteger val)

Translates a BigInteger into a BigDecimal. The scale of the BigDecimal is zero.

参数:

val - BigInteger value to be converted to BigDecimal.

BigDecimal

public BigDecimal(BigInteger val,
                  MathContext mc)

Translates a BigInteger into a BigDecimal rounding according to the context settings. The scale of the BigDecimal is zero.

参数:

val - BigInteger value to be converted to BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(BigInteger unscaledVal,
                  int scale)

Translates a BigInteger unscaled value and an int scale into a BigDecimal. The value of the BigDecimal is (unscaledVal × 10^-scale).

参数:

unscaledVal - unscaled value of the BigDecimal.

scale - scale of the BigDecimal.

BigDecimal

public BigDecimal(BigInteger unscaledVal,
                  int scale,
                  MathContext mc)

Translates a BigInteger unscaled value and an int scale into a BigDecimal, with rounding according to the context settings. The value of the BigDecimal is (unscaledVal × 10^-scale), rounded according to the precision and rounding mode settings.

参数:

unscaledVal - unscaled value of the BigDecimal.

scale - scale of the BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(int val)

Translates an int into a BigDecimal. The scale of the BigDecimal is zero.

参数:

val - int value to be converted to BigDecimal.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(int val,
                  MathContext mc)

Translates an int into a BigDecimal, with rounding according to the context settings. The scale of the BigDecimal, before any rounding, is zero.

参数:

val - int value to be converted to BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(long val)

Translates a long into a BigDecimal. The scale of the BigDecimal is zero.

参数:

val - long value to be converted to BigDecimal.

从以下版本开始:

1.5

BigDecimal

public BigDecimal(long val,
                  MathContext mc)

Translates a long into a BigDecimal, with rounding according to the context settings. The scale of the BigDecimal, before any rounding, is zero.

参数:

val - long value to be converted to BigDecimal.

mc - the context to use.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

方法详细资料

valueOf

public static BigDecimal valueOf(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 BigDecimal values..

参数:

unscaledVal - unscaled value of the BigDecimal.

scale - scale of the BigDecimal.

返回:

a BigDecimal whose value is (unscaledVal × 10^-scale).

valueOf

public static BigDecimal valueOf(long val)

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 BigDecimal values.

参数:

val - value of the BigDecimal.

返回:

a BigDecimal whose value is val.

valueOf

public static BigDecimal valueOf(double val)

Translates a double into a BigDecimal, using the double's canonical string representation provided by the Double#toString(double) method.

Note: This is generally the preferred way to convert a double (or float) into a BigDecimal, as the value returned is equal to that resulting from constructing a BigDecimal from the result of using Double#toString(double).

参数:

val - double to convert to a BigDecimal.

返回:

a BigDecimal whose value is equal to or approximately equal to the value of val.

抛出:

NumberFormatException - if val is infinite or NaN.

从以下版本开始:

1.5

add

public BigDecimal add(BigDecimal augend)

Returns a BigDecimal whose value is (this + augend), and whose scale is max(this.scale(), augend.scale()).

参数:

augend - value to be added to this BigDecimal.

返回:

this + augend

add

public BigDecimal add(BigDecimal augend,
                      MathContext mc)

Returns a BigDecimal whose value is (this + augend), with rounding according to the context settings. If either number is zero and the precision setting is nonzero then the other number, rounded if necessary, is used as the result.

参数:

augend - value to be added to this BigDecimal.

mc - the context to use.

返回:

this + augend, rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

subtract

public BigDecimal subtract(BigDecimal subtrahend)

Returns a BigDecimal whose value is (this - subtrahend), and whose scale is max(this.scale(), subtrahend.scale()).

参数:

subtrahend - value to be subtracted from this BigDecimal.

返回:

this - subtrahend

subtract

public BigDecimal subtract(BigDecimal subtrahend,
                           MathContext mc)

Returns a BigDecimal whose value is (this - subtrahend), with rounding according to the context settings. If subtrahend is zero then this, rounded if necessary, is used as the result. If this is zero then the result is subtrahend.negate(mc).

参数:

subtrahend - value to be subtracted from this BigDecimal.

mc - the context to use.

返回:

this - subtrahend, rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

multiply

public BigDecimal multiply(BigDecimal multiplicand)

Returns a BigDecimal whose value is (this × multiplicand), and whose scale is (this.scale() + multiplicand.scale()).

参数:

multiplicand - value to be multiplied by this BigDecimal.

返回:

this * multiplicand

multiply

public BigDecimal multiply(BigDecimal multiplicand,
                           MathContext mc)

Returns a BigDecimal whose value is (this × multiplicand), with rounding according to the context settings.

参数:

multiplicand - value to be multiplied by this BigDecimal.

mc - the context to use.

返回:

this * multiplicand, rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

divide

public BigDecimal divide(BigDecimal divisor,
                         int scale,
                         int roundingMode)

Returns a BigDecimal whose value is (this / divisor), 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.

The new divide(java.math.BigDecimal,int,java.math.RoundingMode) method should be used in preference to this legacy method.

参数:

divisor - value by which this BigDecimal is to be divided.

scale - scale of the BigDecimal quotient to be returned.

roundingMode - rounding mode to apply.

返回:

this / divisor

抛出:

ArithmeticException - if divisor is zero, roundingMode==ROUND_UNNECESSARY and the specified scale is insufficient to represent the result of the division exactly.

IllegalArgumentException - if roundingMode does not represent a valid rounding mode.

另请参阅:

ROUND_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_UNNECESSARY

divide

public BigDecimal divide(BigDecimal divisor,
                         int scale,
                         RoundingMode roundingMode)

Returns a BigDecimal whose value is (this / divisor), 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.

参数:

divisor - value by which this BigDecimal is to be divided.

scale - scale of the BigDecimal quotient to be returned.

roundingMode - rounding mode to apply.

返回:

this / divisor

抛出:

ArithmeticException - if divisor is zero, roundingMode==RoundingMode.UNNECESSARY and the specified scale is insufficient to represent the result of the division exactly.

从以下版本开始:

1.5

divide

public BigDecimal divide(BigDecimal divisor,
                         int roundingMode)

Returns a BigDecimal whose value is (this / divisor), 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.

The new divide(java.math.BigDecimal,java.math.RoundingMode) method should be used in preference to this legacy method.

参数:

divisor - value by which this BigDecimal is to be divided.

roundingMode - rounding mode to apply.

返回:

this / divisor

抛出:

ArithmeticException - if divisor==0, or roundingMode==ROUND_UNNECESSARY and this.scale() is insufficient to represent the result of the division exactly.

IllegalArgumentException - if roundingMode does not represent a valid rounding mode.

另请参阅:

ROUND_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_UNNECESSARY

divide

public BigDecimal divide(BigDecimal divisor,
                         RoundingMode roundingMode)

Returns a BigDecimal whose value is (this / divisor), 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.

参数:

divisor - value by which this BigDecimal is to be divided.

roundingMode - rounding mode to apply.

返回:

this / divisor

抛出:

ArithmeticException - if divisor==0, or roundingMode==RoundingMode.UNNECESSARY and this.scale() is insufficient to represent the result of the division exactly.

从以下版本开始:

1.5

divide

public BigDecimal divide(BigDecimal divisor)

Returns a BigDecimal whose value is (this / divisor), and whose preferred scale is (this.scale() - divisor.scale()); if the exact quotient cannot be represented (because it has a non-terminating decimal expansion) an ArithmeticException is thrown.

参数:

divisor - value by which this BigDecimal is to be divided.

返回:

this / divisor

抛出:

ArithmeticException - if the exact quotient does not have a terminating decimal expansion

从以下版本开始:

1.5

divide

public BigDecimal divide(BigDecimal divisor,
                         MathContext mc)

Returns a BigDecimal whose value is (this / divisor), with rounding according to the context settings.

参数:

divisor - value by which this BigDecimal is to be divided.

mc - the context to use.

返回:

this / divisor, rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY or mc.precision == 0 and the quotient has a non-terminating decimal expansion.

从以下版本开始:

1.5

divideToIntegralValue

public BigDecimal divideToIntegralValue(BigDecimal divisor)

Returns a BigDecimal whose value is the integer part of the quotient (this / divisor) rounded down. The preferred scale of the result is (this.scale() - divisor.scale()).

参数:

divisor - value by which this BigDecimal is to be divided.

返回:

The integer part of this / divisor.

抛出:

ArithmeticException - if divisor==0

从以下版本开始:

1.5

divideToIntegralValue

public BigDecimal divideToIntegralValue(BigDecimal divisor,
                                        MathContext mc)

Returns a BigDecimal whose value is the integer part of (this / divisor). Since the integer part of the exact quotient does not depend on the rounding mode, the rounding mode does not affect the values returned by this method. The preferred scale of the result is (this.scale() - divisor.scale()). An ArithmeticException is thrown if the integer part of the exact quotient needs more than mc.precision digits.

参数:

divisor - value by which this BigDecimal is to be divided.

mc - the context to use.

返回:

The integer part of this / divisor.

抛出:

ArithmeticException - if divisor==0

ArithmeticException - if mc.precision > 0 and the result requires a precision of more than mc.precision digits.

从以下版本开始:

1.5

remainder

public BigDecimal remainder(BigDecimal divisor)

Returns a BigDecimal whose value is (this % divisor).

The remainder is given by this.subtract(this.divideToIntegralValue(divisor).multiply(divisor)). Note that this is not the modulo operation (the result can be negative).

参数:

divisor - value by which this BigDecimal is to be divided.

返回:

this % divisor.

抛出:

ArithmeticException - if divisor==0

从以下版本开始:

1.5

remainder

public BigDecimal remainder(BigDecimal divisor,
                            MathContext mc)

Returns a BigDecimal whose value is (this % divisor), with rounding according to the context settings. The MathContext settings affect the implicit divide used to compute the remainder. The remainder computation itself is by definition exact. Therefore, the remainder may contain more than mc.getPrecision() digits.

The remainder is given by this.subtract(this.divideToIntegralValue(divisor, mc).multiply(divisor)). Note that this is not the modulo operation (the result can be negative).

参数:

divisor - value by which this BigDecimal is to be divided.

mc - the context to use.

返回:

this % divisor, rounded as necessary.

抛出:

ArithmeticException - if divisor==0

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY, or mc.precision > 0 and the result of this.divideToIntgralValue(divisor) would require a precision of more than mc.precision digits.

从以下版本开始:

1.5

另请参阅:

divideToIntegralValue(java.math.BigDecimal, java.math.MathContext)

divideAndRemainder

public BigDecimal[] divideAndRemainder(BigDecimal divisor)

Returns a two-element BigDecimal array containing the result of divideToIntegralValue followed by the result of remainder on the two operands.

Note that if both the integer quotient and remainder are needed, this method is faster than using the divideToIntegralValue and remainder methods separately because the division need only be carried out once.

参数:

divisor - value by which this BigDecimal is to be divided, and the remainder computed.

返回:

a two element BigDecimal array: the quotient (the result of divideToIntegralValue) is the initial element and the remainder is the final element.

抛出:

ArithmeticException - if divisor==0

从以下版本开始:

1.5

另请参阅:

divideToIntegralValue(java.math.BigDecimal, java.math.MathContext), remainder(java.math.BigDecimal, java.math.MathContext)

divideAndRemainder

public BigDecimal[] divideAndRemainder(BigDecimal divisor,
                                       MathContext mc)

Returns a two-element BigDecimal array containing the result of divideToIntegralValue followed by the result of remainder on the two operands calculated with rounding according to the context settings.

Note that if both the integer quotient and remainder are needed, this method is faster than using the divideToIntegralValue and remainder methods separately because the division need only be carried out once.

参数:

divisor - value by which this BigDecimal is to be divided, and the remainder computed.

mc - the context to use.

返回:

a two element BigDecimal array: the quotient (the result of divideToIntegralValue) is the initial element and the remainder is the final element.

抛出:

ArithmeticException - if divisor==0

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY, or mc.precision > 0 and the result of this.divideToIntgralValue(divisor) would require a precision of more than mc.precision digits.

从以下版本开始:

1.5

另请参阅:

divideToIntegralValue(java.math.BigDecimal, java.math.MathContext), remainder(java.math.BigDecimal, java.math.MathContext)

pow

public BigDecimal pow(int n)

Returns a BigDecimal whose value is (thisⁿ), The power is computed exactly, to unlimited precision.

The parameter n must be in the range 0 through 999999999, inclusive. ZERO.pow(0) returns ONE. Note that future releases may expand the allowable exponent range of this method.

参数:

n - power to raise this BigDecimal to.

返回:

thisⁿ

抛出:

ArithmeticException - if n is out of range.

从以下版本开始:

1.5

pow

public BigDecimal pow(int n,
                      MathContext mc)

Returns a BigDecimal whose value is (thisⁿ). The current implementation uses the core algorithm defined in ANSI standard X3.274-1996 with rounding according to the context settings. In general, the returned numerical value is within two ulps of the exact numerical value for the chosen precision. Note that future releases may use a different algorithm with a decreased allowable error bound and increased allowable exponent range.

The X3.274-1996 algorithm is:

• An ArithmeticException exception is thrown if
  • abs(n) > 999999999
  • mc.precision == 0 and n < 0
  • mc.precision > 0 and n has more than mc.precision decimal digits
• if n is zero, ONE is returned even if this is zero, otherwise
  • if n is positive, the result is calculated via the repeated squaring technique into a single accumulator. The individual multiplications with the accumulator use the same math context settings as in mc except for a precision increased to mc.precision + elength + 1 where elength is the number of decimal digits in n.
  • if n is negative, the result is calculated as if n were positive; this value is then divided into one using the working precision specified above.
  • The final value from either the positive or negative case is then rounded to the destination precision.

参数:

n - power to raise this BigDecimal to.

mc - the context to use.

返回:

thisⁿ using the ANSI standard X3.274-1996 algorithm

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY, or n is out of range.

从以下版本开始:

1.5

abs

public BigDecimal abs()

Returns a BigDecimal whose value is the absolute value of this BigDecimal, and whose scale is this.scale().

返回:

abs(this)

abs

public BigDecimal abs(MathContext mc)

Returns a BigDecimal whose value is the absolute value of this BigDecimal, with rounding according to the context settings.

参数:

mc - the context to use.

返回:

abs(this), rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

negate

public BigDecimal negate()

Returns a BigDecimal whose value is (-this), and whose scale is this.scale().

返回:

-this.

negate

public BigDecimal negate(MathContext mc)

Returns a BigDecimal whose value is (-this), with rounding according to the context settings.

参数:

mc - the context to use.

返回:

-this, rounded as necessary.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

plus

public BigDecimal plus()

Returns a BigDecimal whose value is (+this), and whose scale is this.scale().

This method, which simply returns this BigDecimal is included for symmetry with the unary minus method negate().

返回:

this.

从以下版本开始:

1.5

另请参阅:

negate()

plus

public BigDecimal plus(MathContext mc)

Returns a BigDecimal whose value is (+this), with rounding according to the context settings.

The effect of this method is identical to that of the round(java.math.MathContext) method.

参数:

mc - the context to use.

返回:

this, rounded as necessary. A zero result will have a scale of 0.

抛出:

ArithmeticException - if the result is inexact but the rounding mode is UNNECESSARY.

从以下版本开始:

1.5

另请参阅:

round(MathContext)

signum

public int signum()

Returns the signum function of this BigDecimal.

返回:

-1, 0, or 1 as the value of this BigDecimal is negative, zero, or positive.

scale

public int scale()

Returns the scale of this BigDecimal. If zero or positive, the scale is the number of digits to the right of the decimal point. If negative, the unscaled value of the number is multiplied by ten to the power of the negation of the scale. For example, a scale of -3 means the unscaled value is multiplied by 1000.

返回:

the scale of this BigDecimal.

precision

public int precision()

Returns the precision of this BigDecimal. (The precision is the number of digits in the unscaled value.)

The precision of a zero value is 1.

返回:

the precision of this BigDecimal.

从以下版本开始:

1.5

unscaledValue

public BigInteger unscaledValue()

Returns a BigInteger whose value is the unscaled value of this BigDecimal. (Computes (this * 10^this.scale()).)

返回:

the unscaled value of this BigDecimal.

从以下版本开始:

1.2

round

public BigDecimal round(MathContext mc)

Returns a BigDecimal rounded according to the MathContext settings. If the precision setting is 0 then no rounding takes place.

The effect of this method is identical to that of the plus(java.math.MathContext) method.

参数:

mc - the context to use.

返回:

a BigDecimal rounded according to the MathContext settings.

抛出:

ArithmeticException - if the rounding mode is UNNECESSARY and the BigDecimal operation would require rounding.

从以下版本开始:

1.5

另请参阅:

plus(MathContext)

setScale

public BigDecimal setScale(int newScale,
                           RoundingMode 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.

Note that since BigDecimal objects are immutable, calls of this method do not result in the original object being modified, contrary to the usual convention of having methods named setX mutate field X. Instead, setScale returns an object with the proper scale; the returned object may or may not be newly allocated.

参数:

newScale - scale of the BigDecimal value to be returned.

roundingMode - The rounding mode to apply.

返回:

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.

抛出:

ArithmeticException - if roundingMode==UNNECESSARY and the specified scaling operation would require rounding.

从以下版本开始:

1.5

另请参阅:

RoundingMode

setScale

public BigDecimal setScale(int newScale,
                           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.

Note that since BigDecimal objects are immutable, calls of this method do not result in the original object being modified, contrary to the usual convention of having methods named setX mutate field X. Instead, setScale returns an object with the proper scale; the returned object may or may not be newly allocated.

The new setScale(int,java.math.RoundingMode) method should be used in preference to this legacy method.

参数:

newScale - scale of the BigDecimal value to be returned.

roundingMode - The rounding mode to apply.

返回:

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.

抛出:

ArithmeticException - if roundingMode==ROUND_UNNECESSARY and the specified scaling operation would require rounding.

IllegalArgumentException - if roundingMode does not represent a valid rounding mode.

另请参阅:

ROUND_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_UNNECESSARY

setScale

public BigDecimal setScale(int newScale)

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 changing its value.

This method returns the same result as the two-argument versions of setScale, but saves the caller the trouble of specifying a rounding mode in cases where it is irrelevant.

Note that since BigDecimal objects are immutable, calls of this method do not result in the original object being modified, contrary to the usual convention of having methods named setX mutate field X. Instead, setScale returns an object with the proper scale; the returned object may or may not be newly allocated.

参数:

newScale - scale of the BigDecimal value to be returned.

返回:

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.

抛出:

ArithmeticException - if the specified scaling operation would require rounding.

另请参阅:

setScale(int, int), setScale(int, RoundingMode)

movePointLeft

public BigDecimal movePointLeft(int n)

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).

参数:

n - number of places to move the decimal point to the left.

返回:

a BigDecimal which is equivalent to this one with the decimal point moved n places to the left.

抛出:

ArithmeticException - if scale overflows.

movePointRight

public BigDecimal movePointRight(int n)

Returns a BigDecimal which is equivalent to this one with the decimal point moved n places to the right. If n is non-negative, the call merely subtracts n from the scale. If n is negative, the call is equivalent to movePointLeft(-n). The BigDecimal returned by this call has value (this × 10ⁿ) and scale max(this.scale()-n, 0).

参数:

n - number of places to move the decimal point to the right.

返回:

a BigDecimal which is equivalent to this one with the decimal point moved n places to the right.

抛出:

ArithmeticException - if scale overflows.

scaleByPowerOfTen

public BigDecimal scaleByPowerOfTen(int n)

Returns a BigDecimal whose numerical value is equal to (this * 10ⁿ). The scale of the result is (this.scale() - n).

参数:

n - the exponent power of ten to scale by

返回:

a BigDecimal whose numerical value is equal to (this * 10ⁿ)

抛出:

ArithmeticException - if the scale would be outside the range of a 32-bit integer.

从以下版本开始:

1.5

stripTrailingZeros

public BigDecimal stripTrailingZeros()

Returns a BigDecimal which is numerically equal to this one but with any trailing zeros removed from the representation. For example, stripping the trailing zeros from the BigDecimal value 600.0, which has [BigInteger, scale] components equals to [6000, 1], yields 6E2 with [BigInteger, scale] components equals to [6, -2]. If this BigDecimal is numerically equal to zero, then BigDecimal.ZERO is returned.

返回:

a numerically equal BigDecimal with any trailing zeros removed.

从以下版本开始:

1.5

compareTo

public int compareTo(BigDecimal val)

Compares this BigDecimal with the specified BigDecimal. Two BigDecimal objects 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.

指定者:

compareTo 在接口中 Comparable<BigDecimal>

参数:

val - BigDecimal to which this BigDecimal is to be compared.

返回:

-1, 0, or 1 as this BigDecimal is numerically less than, equal to, or greater than val.

equals

public boolean equals(Object x)

Compares this BigDecimal with the specified Object for equality. Unlike compareTo, this method considers two BigDecimal objects equal only if they are equal in value and scale (thus 2.0 is not equal to 2.00 when compared by this method).

覆盖:

equals 在类中 Object

参数:

x - Object to which this BigDecimal is to be compared.

返回:

true if and only if the specified Object is a BigDecimal whose value and scale are equal to this BigDecimal's.

另请参阅:

compareTo(java.math.BigDecimal), hashCode()

min

public BigDecimal min(BigDecimal val)

Returns the minimum of this BigDecimal and val.

参数:

val - value with which the minimum is to be computed.

返回:

the BigDecimal whose value is the lesser of this BigDecimal and val. If they are equal, as defined by the compareTo method, this is returned.

另请参阅:

compareTo(java.math.BigDecimal)

max

public BigDecimal max(BigDecimal val)

Returns the maximum of this BigDecimal and val.

参数:

val - value with which the maximum is to be computed.

返回:

the BigDecimal whose value is the greater of this BigDecimal and val. If they are equal, as defined by the compareTo method, this is returned.

另请参阅:

compareTo(java.math.BigDecimal)

hashCode

public int hashCode()

Returns the hash code for this BigDecimal. Note that two BigDecimal objects that are numerically equal but differ in scale (like 2.0 and 2.00) will generally not have the same hash code.

覆盖:

hashCode 在类中 Object

返回:

hash code for this BigDecimal.

另请参阅:

equals(Object)

toString

public String toString()

Returns the string representation of this BigDecimal, using scientific notation if an exponent is needed.

A standard canonical string form of the BigDecimal is created as though by the following steps: first, the absolute value of the unscaled value of the BigDecimal is converted to a string in base ten using the characters '0' through '9' with no leading zeros (except if its value is zero, in which case a single '0' character is used).

Next, an adjusted exponent is calculated; this is the negated scale, plus the number of characters in the converted unscaled value, less one. That is, -scale+(ulength-1), where ulength is the length of the absolute value of the unscaled value in decimal digits (its precision).

If the scale is greater than or equal to zero and the adjusted exponent is greater than or equal to -6, the number will be converted to a character form without using exponential notation. In this case, if the scale is zero then no decimal point is added and if the scale is positive a decimal point will be inserted with the scale specifying the number of characters to the right of the decimal point. '0' characters are added to the left of the converted unscaled value as necessary. If no character precedes the decimal point after this insertion then a conventional '0' character is prefixed.

Otherwise (that is, if the scale is negative, or the adjusted exponent is less than -6), the number will be converted to a character form using exponential notation. In this case, if the converted BigInteger has more than one digit a decimal point is inserted after the first digit. An exponent in character form is then suffixed to the converted unscaled value (perhaps with inserted decimal point); this comprises the letter 'E' followed immediately by the adjusted exponent converted to a character form. The latter is in base ten, using the characters '0' through '9' with no leading zeros, and is always prefixed by a sign character '-' ('\u002D') if the adjusted exponent is negative, '+' ('\u002B') otherwise).

Finally, the entire string is prefixed by a minus sign character '-' ('\u002D') if the unscaled value is less than zero. No sign character is prefixed if the unscaled value is zero or positive.

Examples:

For each representation [unscaled value, scale] on the left, the resulting string is shown on the right.

 [123,0]      "123"
 [-123,0]     "-123"
 [123,-1]     "1.23E+3"
 [123,-3]     "1.23E+5"
 [123,1]      "12.3"
 [123,5]      "0.00123"
 [123,10]     "1.23E-8"
 [-123,12]    "-1.23E-10"
 

Notes:

1. There is a one-to-one mapping between the distinguishable BigDecimal values and the result of this conversion. That is, every distinguishable BigDecimal value (unscaled value and scale) has a unique string representation as a result of using toString. If that string representation is converted back to a BigDecimal using the BigDecimal(java.lang.String) constructor, then the original value will be recovered.
2. The string produced for a given number is always the same; it is not affected by locale. This means that it can be used as a canonical string representation for exchanging decimal data, or as a key for a Hashtable, etc. Locale-sensitive number formatting and parsing is handled by the NumberFormat class and its subclasses.
3. The toEngineeringString() method may be used for presenting numbers with exponents in engineering notation, and the setScale method may be used for rounding a BigDecimal so it has a known number of digits after the decimal point.
4. The digit-to-character mapping provided by Character.forDigit is used.

覆盖:

toString 在类中 Object

返回:

string representation of this BigDecimal.

另请参阅:

Character.forDigit(int, int), BigDecimal(java.lang.String)

toEngineeringString

public String toEngineeringString()

Returns a string representation of this BigDecimal, using engineering notation if an exponent is needed.

Returns a string that represents the BigDecimal as described in the toString() method, except that if exponential notation is used, the power of ten is adjusted to be a multiple of three (engineering notation) such that the integer part of nonzero values will be in the range 1 through 999. If exponential notation is used for zero values, a decimal point and one or two fractional zero digits are used so that the scale of the zero value is preserved. Note that unlike the output of toString(), the output of this method is not guaranteed to recover the same [integer, scale] pair of this BigDecimal if the output string is converting back to a BigDecimal using the string constructor. The result of this method meets the weaker constraint of always producing a numerically equal result from applying the string constructor to the method's output.

返回:

string representation of this BigDecimal, using engineering notation if an exponent is needed.

从以下版本开始:

1.5

toPlainString

public String toPlainString()

Returns a string representation of this BigDecimal without an exponent field. For values with a positive scale, the number of digits to the right of the decimal point is used to indicate scale. For values with a zero or negative scale, the resulting string is generated as if the value were converted to a numerically equal value with zero scale and as if all the trailing zeros of the zero scale value were present in the result. The entire string is prefixed by a minus sign character '-' ('\u002D') if the unscaled value is less than zero. No sign character is prefixed if the unscaled value is zero or positive. Note that if the result of this method is passed to the string constructor, only the numerical value of this BigDecimal will necessarily be recovered; the representation of the new BigDecimal may have a different scale. In particular, if this BigDecimal has a negative scale, the string resulting from this method will have a scale of zero when processed by the string constructor. (This method behaves analogously to the toString method in 1.4 and earlier releases.)

返回:

a string representation of this BigDecimal without an exponent field.

从以下版本开始:

1.5

另请参阅:

toString(), toEngineeringString()

toBigInteger

public BigInteger toBigInteger()

Converts this BigDecimal to a BigInteger. This conversion is analogous to the narrowing primitive conversion from double to long as defined in section 5.1.3 of The Java™ Language Specification: any fractional part of this BigDecimal will be discarded. Note that this conversion can lose information about the precision of the BigDecimal value.

To have an exception thrown if the conversion is inexact (in other words if a nonzero fractional part is discarded), use the toBigIntegerExact() method.

返回:

this BigDecimal converted to a BigInteger.

toBigIntegerExact

public BigInteger toBigIntegerExact()

Converts this BigDecimal to a BigInteger, checking for lost information. An exception is thrown if this BigDecimal has a nonzero fractional part.

返回:

this BigDecimal converted to a BigInteger.

抛出:

ArithmeticException - if this has a nonzero fractional part.

从以下版本开始:

1.5

longValue

public long longValue()

Converts this BigDecimal to a long. This conversion is analogous to the narrowing primitive conversion from double to short as defined in section 5.1.3 of 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. Note that this conversion can lose information about the overall magnitude and precision of this BigDecimal value as well as return a result with the opposite sign.

指定者:

longValue 在类中 Number

返回:

this BigDecimal converted to a long.

longValueExact

public long longValueExact()

Converts this BigDecimal to a long, checking for lost information. If this BigDecimal has a nonzero fractional part or is out of the possible range for a long result then an ArithmeticException is thrown.

返回:

this BigDecimal converted to a long.

抛出:

ArithmeticException - if this has a nonzero fractional part, or will not fit in a long.

从以下版本开始:

1.5

intValue

public int intValue()

Converts this BigDecimal to an int. This conversion is analogous to the narrowing primitive conversion from double to short as defined in section 5.1.3 of 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. Note that this conversion can lose information about the overall magnitude and precision of this BigDecimal value as well as return a result with the opposite sign.

指定者:

intValue 在类中 Number

返回:

this BigDecimal converted to an int.

intValueExact

public int intValueExact()

Converts this BigDecimal to an int, checking for lost information. If this BigDecimal has a nonzero fractional part or is out of the possible range for an int result then an ArithmeticException is thrown.

返回:

this BigDecimal converted to an int.

抛出:

ArithmeticException - if this has a nonzero fractional part, or will not fit in an int.

从以下版本开始:

1.5

shortValueExact

public short shortValueExact()

Converts this BigDecimal to a short, checking for lost information. If this BigDecimal has a nonzero fractional part or is out of the possible range for a short result then an ArithmeticException is thrown.

返回:

this BigDecimal converted to a short.

抛出:

ArithmeticException - if this has a nonzero fractional part, or will not fit in a short.

从以下版本开始:

1.5

byteValueExact

public byte byteValueExact()

Converts this BigDecimal to a byte, checking for lost information. If this BigDecimal has a nonzero fractional part or is out of the possible range for a byte result then an ArithmeticException is thrown.

返回:

this BigDecimal converted to a byte.

抛出:

ArithmeticException - if this has a nonzero fractional part, or will not fit in a byte.

从以下版本开始:

1.5

floatValue

public float floatValue()

Converts this BigDecimal to a float. This conversion is similar to the narrowing primitive conversion from double to float as defined in section 5.1.3 of 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. Note that even when the return value is finite, this conversion can lose information about the precision of the BigDecimal value.

指定者:

floatValue 在类中 Number

返回:

this BigDecimal converted to a float.

doubleValue

public double doubleValue()

Converts this BigDecimal to a double. This conversion is similar to the narrowing primitive conversion from double to float as defined in section 5.1.3 of The Java™ Language Specification: if this BigDecimal has too great a magnitude represent as a double, it will be converted to Double#NEGATIVE_INFINITY or Double#POSITIVE_INFINITY as appropriate. Note that even when the return value is finite, this conversion can lose information about the precision of the BigDecimal value.

指定者:

doubleValue 在类中 Number

返回:

this BigDecimal converted to a double.

ulp

public BigDecimal ulp()

Returns the size of an ulp, a unit in the last place, of this BigDecimal. An ulp of a nonzero BigDecimal value is the positive distance between this value and the BigDecimal value next larger in magnitude with the same number of digits. An ulp of a zero value is numerically equal to 1 with the scale of this. The result is stored with the same scale as this so the result for zero and nonzero values is equal to [1, this.scale()].

返回:

the size of an ulp of this

从以下版本开始:

1.5