bigdecimal 保留小数位

 1 public class test1_format {
 2 
 3     public static void main(String[] args) {
 4         BigDecimal decimal = new BigDecimal("1.12345");
 5         System.out.println(decimal);
 6         BigDecimal setScale = decimal.setScale(4,BigDecimal.ROUND_HALF_DOWN);
 7         System.out.println(setScale);
 8         
 9         BigDecimal setScale1 = decimal.setScale(4,BigDecimal.ROUND_HALF_UP);
10         System.out.println(setScale1);
11     }
12 }

参数定义

ROUND_CEILING
Rounding mode to round towards positive infinity.
向正无穷方向舍入

ROUND_DOWN
Rounding mode to round towards zero.
向零方向舍入

ROUND_FLOOR
Rounding mode to round towards negative infinity.
向负无穷方向舍入

ROUND_HALF_DOWN
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round down.
向（距离）最近的一边舍入，除非两边（的距离）是相等,如果是这样，向下舍入, 例如1.55 保留一位小数结果为1.5

ROUND_HALF_EVEN
Rounding mode to round towards the "nearest neighbor" unless both neighbors are equidistant, in which case, round towards the even neighbor.
向（距离）最近的一边舍入，除非两边（的距离）是相等,如果是这样，如果保留位数是奇数，使用ROUND_HALF_UP ，如果是偶数，使用ROUND_HALF_DOWN

ROUND_HALF_UP
Rounding mode to round towards "nearest neighbor" unless both neighbors are equidistant, in which case round up.
向（距离）最近的一边舍入，除非两边（的距离）是相等,如果是这样，向上舍入, 1.55保留一位小数结果为1.6

ROUND_UNNECESSARY
Rounding mode to assert that the requested operation has an exact result, hence no rounding is necessary.
计算结果是精确的，不需要舍入模式

ROUND_UP
Rounding mode to round away from zero.
向远离0的方向舍入