BigDecimal保留小数位

public class BigDecimalFormat {

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

        BigDecimal scale2 = decimal.setScale(4, BigDecimal.ROUND_HALF_UP);
        System.out.println(scale2);
    }
}

BigDecimal.setScale()方法用于格式化小数点

setScale(1) 表示保留一位小数，默认用四舍五入方式
setScale(1, BigDecimal.ROUND_DOWN) 直接删除多余的小数位，如2.35会变成2.3
setScale(1, BigDecimal.ROUND_UP) 进位处理，2.35变成2.4
setScale(1, BigDecimal.ROUND_HALF_UP) 四舍五入，2.35变成2.4
setScale(1, BigDecimal.ROUND_HALF_DOWN) 五舍六入，2.35变成2.3

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