android如何保留小数点后x位数字

static long round(double a)Returns the closest long to the argument.
static int round(float a)Returns the closest int to the argument
精确的,是这样.
/**
* 提供精确的小数位四舍五入处理.
*
* @param v
*需要四舍五入的数字
* @param scale
*小数点后保留几位
* @return 四舍五入后的结果
*/
public static double round(Double v, int scale) {
if (scale throw new IllegalArgumentException("The scale must be a positive integer or zero");
}
BigDecimal b = null == v ? new BigDecimal("0.0") : new BigDecimal(Double.toString(v));
BigDecimal one = new BigDecimal("1");
return b.divide(one, scale, BigDecimal.ROUND_HALF_UP).doubleValue();