在java中,半向下和半向上有什么不同?
Java代码:在java中,半向下和半向上有什么不同?,java,Java,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,R
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
问题:
为什么RoundingMode.HALF\u DOWN和RoundingMode.HALF\u UP的输出是相同的?嗯,
RoundingMode.HALF\u DOWN的javadoc说:
如果丢弃的分数>0.5,则其行为与RoundingMode.UP相同;否则,其行为与RoundingMode.DOWN相同
而RoundingMode.HALF_UP
的Javadoc说:
如果丢弃的分数为,则其行为与RoundingMode.UP相同≥ 0.5; 否则,其行为与RoundingMode.DOWN相同
在您的示例中,第二个和第三个除法中被丢弃的分数为0.5217391304347826086952521739,大于0.5,因此这两个除法的行为都是RoundingMode.UP
只有当丢弃的分数正好为0.5时,才会看到不同的结果
例如,以下各项:
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
嗯,RoundingMode.HALF_DOWN的javadoc说:
如果丢弃的分数>0.5,则其行为与RoundingMode.UP相同;否则,其行为与RoundingMode.DOWN相同
而RoundingMode.HALF_UP
的Javadoc说:
如果丢弃的分数为,则其行为与RoundingMode.UP相同≥ 0.5; 否则,其行为与RoundingMode.DOWN相同
在您的示例中,第二个和第三个除法中被丢弃的分数为0.5217391304347826086952521739,大于0.5,因此这两个除法的行为都是RoundingMode.UP
只有当丢弃的分数正好为0.5时,才会看到不同的结果
例如,以下各项:
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
你可以说,对于0.5(“一半:)一半向上舍入,一半向下舍入。你可以说,对于0.5(“一半:)一半向上舍入,一半向下舍入。