不可变的、任意精度的有符号十进制数。表示的数字的值BigDecimal是(unscaledValue × 10^-scale )。
BigDecimal类使用户可以完全控制舍入行为。如果没有指定取整方式，无法表示准确的结果，则抛出异常；否则，可以通过MathContext操作提供适当的对象来执行所选精度和舍入模式的计算。(使用RoundingMode的枚举值控制舍入)
两种控制位数的方式：缩放/舍入操作(setScalend round)；其值大约（或完全）等于操作数的值，但其比例或精度是指定值（也就是说，它们增加或减少存储数字的精度，而对其值的影响最小）;小数点移动操作(movePointLeft和movePointRight):通过将小数点沿指定方向移动指定距离操作数
| Constructor | Description |
|---|---|
| BigDecimal(BinInteger 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) | TTranslates 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 |
| BigDecimal(char[] in) | Translates a character array representation of a BigDecimal into a BigDecimal, accepting the same sequence of characters as the BigDecimal(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(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(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(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(String) constructor, with rounding according to the context settings |
| Method | Description |
|---|---|
| (BigDecimal)abs() | Returns a BigDecimal whose value is the absolute value of this BigDecimal, and whose scale is this.scale() |
| (BigDecimal)add(BigDecimal augend) | Returns a BigDecimal whose value is (this + augend), and whose scale is max(this.scale(), augend.scale()) |
| (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() |
| (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)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 (this^n), The power is computed exactly, to unlimited precision |
| (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)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)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 |
更多内容请参考链接：https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html
