BigDecimal 保留小数位

public class test1_format {

    public static void main(String[] args) {
        BigDecimal decimal = new BigDecimal("1.12345");
        System.out.println(decimal);
        BigDecimal setScale = decimal.setScale(4,BigDecimal.ROUND_HALF_DOWN);
        System.out.println(setScale);
        
        BigDecimal setScale1 = decimal.setScale(4,BigDecimal.ROUND_HALF_UP);
        System.out.println(setScale1);
    }
}

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