JAVA的HALF_DOWN和HALF_UP的区别?
Java代码:
public class BigDecimalDemo { public static void main(String[] args) { BigDecimal bd2=BigDecimal.valueOf(11); BigDecimal bd3=new BigDecimal("2.3"); BigDecimal bdDiv = bd2.divide(bd3,38,RoundingMode.HALF_UP); System.out.println(bdDiv); BigDecimal bdDivDOWN = bd2.divide(bd3,10, RoundingMode.HALF_DOWN); System.out.println(bdDivDOWN); BigDecimal bdDivUP = bd2.divide(bd3,10, RoundingMode.HALF_UP); System.out.println(bdDivUP); } }
输出:
4.78260869565217391304347826086956521739 4.7826086957 4.7826086957
题:
RoundingMode.HALF_DOWN和RoundingMode.HALF_UP的输出为何相同?
最佳答案
好吧,RoundingMode.HALF_DOWN
的javadoc说:
1、如果舍弃的分数> 0.5,则表现为RoundingMode.UP;否则,其行为与RoundingMode.DOWN相同。
而RoundingMode.HALF_UP
的Javadoc说:
2、如果舍弃分数≥0.5,则表现为RoundingMode.UP;否则,表现为RoundingMode.DOWN
在您的示例中,第二级和第三级中的废弃分数是0.5217391304347826086956521739,该分数> 0.5,因此两者的行为均RoundingMode.UP
。
仅当丢弃分数精确为0.5时,您才会看到不同的结果。
例如,以下内容:
BigDecimal bd2=BigDecimal.valueOf(11.12345678955); BigDecimal bd3=new BigDecimal("1"); BigDecimal bdDiv = bd2.divide(bd3,38,RoundingMode.HALF_UP); System.out.println(bdDiv); BigDecimal bdDivDOWN = bd2.divide(bd3,10, RoundingMode.HALF_DOWN); System.out.println(bdDivDOWN); BigDecimal bdDivUP = bd2.divide(bd3,10, RoundingMode.HALF_UP); System.out.println(bdDivUP);
将输出:
11.12345678955000000000000000000000000000 11.1234567895 11.1234567896
转自:java - Java中的HALF_DOWN和HALF_UP有什么区别? | RoundingMode (lmlphp.com)