BigDecimal比较大小

   这个类是java里精确计算的类，下面说一下两个BigDecimal对象大小，相等的判断

   1 比较对象是否相等

     一般的对象用equals，但是BigDecimal比较特殊，举个例子：

     BigDecimal a=BigDecimal.valueOf(1.0);

     BigDecimal b=BigDecimal.valueOf(1.000);

     在现实中这两个数字是相等的，但是如果用

     a.equals(b)结果是false;怎么不相等了呢？因为equals是比较内容，“1.0”和“1.000”当然不一样了

     解决办法：

            if(a.compareTo(b)==0) 结果是true

     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.

    Specified by:

    compareTo in interface Comparable<BigDecimal>

    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.

    简单翻译：

           结果是

-1 小于  

0 等于

1 大于