兩個BigDecimal對象大小，相等的判斷：一般的對象用equals，但是BigDecimal比較特殊，舉個例子：
     BigDecimal a=BigDecimal.valueOf(1.0);
     BigDecimal b=BigDecimal.valueOf(1.000);
     在現(xiàn)實(shí)中這兩個數(shù)字是相等的，但是問題來來了。a.equals(b)結(jié)果是false;怎么不相等了呢？

    解決方法：
   if(a.compareTo(b)==0)結(jié)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.
    簡單翻譯：
           結(jié)果是  -1 小于 、 0 等于 、 1 大于。