BigDecimal一般是用来做要求比较高的精准计算的。前几天在使用的时候遇到一个大坑，记录下。

这个问题产生是使用BigDecimal做除法(divide)运算，这个类的divide方法存在三个常用的构造函数。

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](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html)

**[divide](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html%23divide%28java.math.BigDecimal%2C%2520int%29)**([BigDecimal](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html) divisor, int roundingMode) 
          Returns a BigDecimal whose value is (this / divisor), and whose scale is this.scale().

[BigDecimal](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html)

**[divide](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html%23divide%28java.math.BigDecimal%2C%2520int%2C%2520int%29)**([BigDecimal](https://www.oschina.net/action/GoToLink?url=https%3A%2F%2Fdocs.oracle.com%2Fjavase%2F6%2Fdocs%2Fapi%2Fjava%2Fmath%2FBigDecimal.html) divisor, int scale, int roundingMode) 
          Returns a BigDecimal whose value is (this / divisor), and whose scale is as specified.

在第一个构造方法中，可以只传入被除数（divisor）。但是调用这个方法极容易出现一个错误，当除不尽时候，会产生无限循环小数，这时将会抛出异常：

java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.

at java.math.BigDecimal.divide(BigDecimal.java:1690)

在第二个或者第三个构造方法中，指定了当除不尽的时候，进行有效位数的保留，因此会比较安全。

在此推荐大家使用这个方法的时候  使用第三个方法，比较安全。