Java中的RoundingMode舍入模式详解

import java.math.BigDecimal;  
import java.math.RoundingMode;  
public class RoundingModeTest {  
    public static void main(String[] args) {  
        BigDecimal value = new BigDecimal("2.555");  
        // RoundingMode.UP 指定位向上取整  
        System.out.println("RoundingMode.UP 指定位向上取整");  
        System.out.println(value.setScale(0,RoundingMode.UP));  
        System.out.println(value.setScale(1,RoundingMode.UP));  
        // RoundingMode.UP 指定位向下取整  
        System.out.println("RoundingMode.DOWN 指定位向下取整");  
        System.out.println(value.setScale(0,RoundingMode.DOWN));  
        System.out.println(value.setScale(1,RoundingMode.DOWN));  
        // RoundingMode.CEILING 指定位向最近整数取整，如果距离两边一样远，则向上取整      
System.out.println("RoundingMode.CEILING 指定位向最近整数取整，如果距离两边一样远，则向上取整");  
        System.out.println(value.setScale(0,RoundingMode.CEILING));  
        System.out.println(value.setScale(1,RoundingMode.CEILING));  
        System.out.println(value.setScale(2,RoundingMode.CEILING));  
        // RoundingMode.FLOOR 指定位向最近整数取整，如果距离两边一样远，则向下取整  
        System.out.println("RoundingMode.FLOOR 指定位向最近整数取整，如果距离两边一样远，则向下取整");  
        System.out.println(value.setScale(0,RoundingMode.FLOOR));  
        System.out.println(value.setScale(1,RoundingMode.FLOOR));  
        System.out.println(value.setScale(2,RoundingMode.FLOOR));  
        // RoundingMode.HALF_UP 四舍五入  
        System.out.println("RoundingMode.HALF_UP 四舍五入");  
        System.out.println(value.setScale(0,RoundingMode.HALF_UP));  
        System.out.println(value.setScale(1,RoundingMode.HALF_UP));  
        System.out.println(value.setScale(2,RoundingMode.HALF_UP));  
        // RoundingMode.HALF_DOWN 五舍六入  
        System.out.println("RoundingMode.HALF_DOWN 五舍六入");  
        System.out.println(value.setScale(0,RoundingMode.HALF_DOWN));  
        System.out.println(value.setScale(1,RoundingMode.HALF_DOWN));  
        System.out.println(value.setScale(2,RoundingMode.HALF_DOWN));  
        // RoundingMode.HALF_EVEN 银行家舍入，四舍六入，五成双，看前一位  
        System.out.println("RoundingMode.HALF_EVEN 银行家舍入，四舍六入，五成双，看前一位");  
        System.out.println(value.setScale(0,RoundingMode.HALF_EVEN));  
        System.out.println(value.setScale(1,RoundingMode.HALF_EVEN));  
        System.out.println(value.setScale(2,RoundingMode.HALF_EVEN));  
        // RoundingMode.UNNECESSARY 不进行舍入，如果舍入位不为0，则抛出ArithmeticException异常  
        System.out.println("RoundingMode.UNNECESSARY 不进行舍入，如果舍入位不为0，则抛出ArithmeticException异常");  
    }  
}

RoundingMode.UP 指定位向上取整
3
2.6
RoundingMode.DOWN 指定位向下取整
2
2.5
RoundingMode.CEILING 指定位向最近整数取整，如果距离两边一样远，则向上取整
3
2.6
2.56
RoundingMode.FLOOR 指定位向最近整数取整，如果距离两边一样远，则向下取整
2
2.5
2.55
RoundingMode.HALF_UP 四舍五入
3
2.6
2.56
RoundingMode.HALF_DOWN 五舍六入
3
2.6
2.55
RoundingMode.HALF_EVEN 银行家舍入，四舍六入，五成双，看前一位
3
2.6
2.56
RoundingMode.UNNECESSARY 不进行舍入，如果舍入位不为0，则抛出ArithmeticException异常