BigDecimal 小数位的处理(RoundingMode)

2024-06-24 03:36

本文主要是介绍BigDecimal 小数位的处理(RoundingMode),希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!

前言:

在日常项目开发中,接触小数是常有的事情,而产品对于小数的处理,在不同的业务中有不同的定义,比如四舍五入、截取、向上舍位、向下舍位等等场景,面对如此多的场景,你是否会束手无策?或者说自己去研究怎么实现?其实 Java 已经给我们提供了一个枚举类 RoundingMode,RoundingMode 共有 8 种舍位方式,本篇我们来逐个分析。

RoundingMode 枚举类源码如下:

package java.math;/**** @see     BigDecimal* @see     MathContext* @author  Josh Bloch* @author  Mike Cowlishaw* @author  Joseph D. Darcy* @since 1.5*/
public enum RoundingMode {/*** Rounding mode to round away from zero.  Always increments the* digit prior to a non-zero discarded fraction.  Note that this* rounding mode never decreases the magnitude of the calculated* value.**<p>Example:*<table border>* <caption><b>Rounding mode UP Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code UP} rounding*<tr align=right><td>5.5</td>  <td>6</td>*<tr align=right><td>2.5</td>  <td>3</td>*<tr align=right><td>1.6</td>  <td>2</td>*<tr align=right><td>1.1</td>  <td>2</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-2</td>*<tr align=right><td>-1.6</td> <td>-2</td>*<tr align=right><td>-2.5</td> <td>-3</td>*<tr align=right><td>-5.5</td> <td>-6</td>*</table>*/UP(BigDecimal.ROUND_UP),/*** Rounding mode to round towards zero.  Never increments the digit* prior to a discarded fraction (i.e., truncates).  Note that this* rounding mode never increases the magnitude of the calculated value.**<p>Example:*<table border>* <caption><b>Rounding mode DOWN Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code DOWN} rounding*<tr align=right><td>5.5</td>  <td>5</td>*<tr align=right><td>2.5</td>  <td>2</td>*<tr align=right><td>1.6</td>  <td>1</td>*<tr align=right><td>1.1</td>  <td>1</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-1</td>*<tr align=right><td>-1.6</td> <td>-1</td>*<tr align=right><td>-2.5</td> <td>-2</td>*<tr align=right><td>-5.5</td> <td>-5</td>*</table>*/DOWN(BigDecimal.ROUND_DOWN),/*** Rounding mode to round towards positive infinity.  If the* result is positive, behaves as for {@code RoundingMode.UP};* if negative, behaves as for {@code RoundingMode.DOWN}.  Note* that this rounding mode never decreases the calculated value.**<p>Example:*<table border>* <caption><b>Rounding mode CEILING Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code CEILING} rounding*<tr align=right><td>5.5</td>  <td>6</td>*<tr align=right><td>2.5</td>  <td>3</td>*<tr align=right><td>1.6</td>  <td>2</td>*<tr align=right><td>1.1</td>  <td>2</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-1</td>*<tr align=right><td>-1.6</td> <td>-1</td>*<tr align=right><td>-2.5</td> <td>-2</td>*<tr align=right><td>-5.5</td> <td>-5</td>*</table>*/CEILING(BigDecimal.ROUND_CEILING),/*** Rounding mode to round towards negative infinity.  If the* result is positive, behave as for {@code RoundingMode.DOWN};* if negative, behave as for {@code RoundingMode.UP}.  Note that* this rounding mode never increases the calculated value.**<p>Example:*<table border>* <caption><b>Rounding mode FLOOR Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code FLOOR} rounding*<tr align=right><td>5.5</td>  <td>5</td>*<tr align=right><td>2.5</td>  <td>2</td>*<tr align=right><td>1.6</td>  <td>1</td>*<tr align=right><td>1.1</td>  <td>1</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-2</td>*<tr align=right><td>-1.6</td> <td>-2</td>*<tr align=right><td>-2.5</td> <td>-3</td>*<tr align=right><td>-5.5</td> <td>-6</td>*</table>*/FLOOR(BigDecimal.ROUND_FLOOR),/*** Rounding mode to round towards {@literal "nearest neighbor"}* unless both neighbors are equidistant, in which case round up.* Behaves as for {@code RoundingMode.UP} if the discarded* fraction is &ge; 0.5; otherwise, behaves as for* {@code RoundingMode.DOWN}.  Note that this is the rounding* mode commonly taught at school.**<p>Example:*<table border>* <caption><b>Rounding mode HALF_UP Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code HALF_UP} rounding*<tr align=right><td>5.5</td>  <td>6</td>*<tr align=right><td>2.5</td>  <td>3</td>*<tr align=right><td>1.6</td>  <td>2</td>*<tr align=right><td>1.1</td>  <td>1</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-1</td>*<tr align=right><td>-1.6</td> <td>-2</td>*<tr align=right><td>-2.5</td> <td>-3</td>*<tr align=right><td>-5.5</td> <td>-6</td>*</table>*/HALF_UP(BigDecimal.ROUND_HALF_UP),/*** Rounding mode to round towards {@literal "nearest neighbor"}* unless both neighbors are equidistant, in which case round* down.  Behaves as for {@code RoundingMode.UP} if the discarded* fraction is &gt; 0.5; otherwise, behaves as for* {@code RoundingMode.DOWN}.**<p>Example:*<table border>* <caption><b>Rounding mode HALF_DOWN Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code HALF_DOWN} rounding*<tr align=right><td>5.5</td>  <td>5</td>*<tr align=right><td>2.5</td>  <td>2</td>*<tr align=right><td>1.6</td>  <td>2</td>*<tr align=right><td>1.1</td>  <td>1</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-1</td>*<tr align=right><td>-1.6</td> <td>-2</td>*<tr align=right><td>-2.5</td> <td>-2</td>*<tr align=right><td>-5.5</td> <td>-5</td>*</table>*/HALF_DOWN(BigDecimal.ROUND_HALF_DOWN),/*** Rounding mode to round towards the {@literal "nearest neighbor"}* unless both neighbors are equidistant, in which case, round* towards the even neighbor.  Behaves as for* {@code RoundingMode.HALF_UP} if the digit to the left of the* discarded fraction is odd; behaves as for* {@code RoundingMode.HALF_DOWN} if it's even.  Note that this* is the rounding mode that statistically minimizes cumulative* error when applied repeatedly over a sequence of calculations.* It is sometimes known as {@literal "Banker's rounding,"} and is* chiefly used in the USA.  This rounding mode is analogous to* the rounding policy used for {@code float} and {@code double}* arithmetic in Java.**<p>Example:*<table border>* <caption><b>Rounding mode HALF_EVEN Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code HALF_EVEN} rounding*<tr align=right><td>5.5</td>  <td>6</td>*<tr align=right><td>2.5</td>  <td>2</td>*<tr align=right><td>1.6</td>  <td>2</td>*<tr align=right><td>1.1</td>  <td>1</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>-1</td>*<tr align=right><td>-1.6</td> <td>-2</td>*<tr align=right><td>-2.5</td> <td>-2</td>*<tr align=right><td>-5.5</td> <td>-6</td>*</table>*/HALF_EVEN(BigDecimal.ROUND_HALF_EVEN),/*** Rounding mode to assert that the requested operation has an exact* result, hence no rounding is necessary.  If this rounding mode is* specified on an operation that yields an inexact result, an* {@code ArithmeticException} is thrown.*<p>Example:*<table border>* <caption><b>Rounding mode UNNECESSARY Examples</b></caption>*<tr valign=top><th>Input Number</th>*    <th>Input rounded to one digit<br> with {@code UNNECESSARY} rounding*<tr align=right><td>5.5</td>  <td>throw {@code ArithmeticException}</td>*<tr align=right><td>2.5</td>  <td>throw {@code ArithmeticException}</td>*<tr align=right><td>1.6</td>  <td>throw {@code ArithmeticException}</td>*<tr align=right><td>1.1</td>  <td>throw {@code ArithmeticException}</td>*<tr align=right><td>1.0</td>  <td>1</td>*<tr align=right><td>-1.0</td> <td>-1</td>*<tr align=right><td>-1.1</td> <td>throw {@code ArithmeticException}</td>*<tr align=right><td>-1.6</td> <td>throw {@code ArithmeticException}</td>*<tr align=right><td>-2.5</td> <td>throw {@code ArithmeticException}</td>*<tr align=right><td>-5.5</td> <td>throw {@code ArithmeticException}</td>*</table>*/UNNECESSARY(BigDecimal.ROUND_UNNECESSARY);// Corresponding BigDecimal rounding constantfinal int oldMode;/*** Constructor** @param oldMode The {@code BigDecimal} constant corresponding to*        this mode*/private RoundingMode(int oldMode) {this.oldMode = oldMode;}/*** Returns the {@code RoundingMode} object corresponding to a* legacy integer rounding mode constant in {@link BigDecimal}.** @param  rm legacy integer rounding mode to convert* @return {@code RoundingMode} corresponding to the given integer.* @throws IllegalArgumentException integer is out of range*/public static RoundingMode valueOf(int rm) {switch(rm) {case BigDecimal.ROUND_UP:return UP;case BigDecimal.ROUND_DOWN:return DOWN;case BigDecimal.ROUND_CEILING:return CEILING;case BigDecimal.ROUND_FLOOR:return FLOOR;case BigDecimal.ROUND_HALF_UP:return HALF_UP;case BigDecimal.ROUND_HALF_DOWN:return HALF_DOWN;case BigDecimal.ROUND_HALF_EVEN:return HALF_EVEN;case BigDecimal.ROUND_UNNECESSARY:return UNNECESSARY;default:throw new IllegalArgumentException("argument out of range");}}
}

8种舍位模式含义解析:

  • RoundingMode.UP:正数向上舍位,负数向下舍位。
  • RoundingMode.DOWN:直接保留指定位数数字,可以理解为截取。
  • RoundingMode.CEILING:直译是天花板的意思,正数的效果如同 RoundingMode.UP,负数的效果如同 RoundingMode.DOWN。
  • RoundingMode.FLOOR:直译是地板的意思,和 RoundingMode.CEILING 刚好相反,正数的效果如同 RoundingMode.DOWN,负数的效果如同 RoundingMode.UP。
  • RoundingMode.HALF_UP:就是比较常见的四舍五入。
  • RoundingMode.HALF_DOWN:五舍六入。
  • RoundingMode.HALF_EVEN:指定位数后面的小数是5,且5后面有数字且这些数字不全部为0,则进一位,否则看5前面的一位,如果是奇数就进一位,如果是偶数则不进位,其他情况四舍五入。
  • RoundingMode.UNNECESSARY:指定位数后没有数字或者全部是0,否则会抛出异常。

RoundingMode.UP 验证:

BigDecimal bigDecimal1 = new BigDecimal("1.235");
BigDecimal up1 = bigDecimal1.setScale(2, RoundingMode.UP);
BigDecimal bigDecimal2 = new BigDecimal("-1.233");
BigDecimal up2 = bigDecimal2.setScale(2, RoundingMode.UP);
System.out.println("up1:" + up1);
System.out.println("up2:" + up2);

执行结果:

up1:1.24
up2:-1.24

正数向上舍位,负数向下舍位,符合预期。

RoundingMode.HALF_DOWN 验证:

BigDecimal down = new BigDecimal("1.235").setScale(2, RoundingMode.DOWN);
System.out.println("down:" + down);

执行结果:

down:1.23

截取直接保留指定位数数字,符合预期。

RoundingMode.CEILING 验证:

BigDecimal ceilingOne = new BigDecimal("1.235").setScale(2, RoundingMode.CEILING);
BigDecimal ceilingTwo = new BigDecimal("-1.235").setScale(2, RoundingMode.CEILING);
System.out.println("ceilingOne:" + ceilingOne);
System.out.println("ceilingTwo:" + ceilingTwo);

执行结果:

ceilingOne:1.24
ceilingTwo:-1.23

正数向上舍位,负数直接截取,符合预期。

RoundingMode.FLOOR 验证:

BigDecimal floorOne = new BigDecimal("1.235").setScale(2, RoundingMode.FLOOR);
BigDecimal floorTwo = new BigDecimal("-1.235").setScale(2, RoundingMode.FLOOR);
System.out.println("floorOne:" + floorOne);
System.out.println("floorTwo:" + floorTwo);

执行结果:

floorOne:1.23
floorTwo:-1.24

正数截取,负数向下舍位,符合预期。

RoundingMode.HALF_UP 验证:

BigDecimal halfUpOne = new BigDecimal("1.235").setScale(2, RoundingMode.HALF_UP);
BigDecimal halfUpTwo = new BigDecimal("1.234").setScale(2, RoundingMode.HALF_UP);
System.out.println("halfUpOne:" + halfUpOne);
System.out.println("halfUpTwo:" + halfUpTwo);

执行结果:

halfUpOne:1.24
halfUpTwo:1.23

四舍五入,符合预期。

RoundingMode.HALF_EVEN 验证:

BigDecimal halfEvenOne = new BigDecimal("1.2351").setScale(2, RoundingMode.HALF_EVEN);
BigDecimal halfEvenTwo = new BigDecimal("1.2250").setScale(2, RoundingMode.HALF_EVEN);
BigDecimal halfEvenThree = new BigDecimal("1.2350").setScale(2, RoundingMode.HALF_EVEN);
BigDecimal halfEvenFour = new BigDecimal("1.2450").setScale(2, RoundingMode.HALF_EVEN);
BigDecimal halfEvenFive = new BigDecimal("1.244").setScale(2, RoundingMode.HALF_EVEN);
BigDecimal halfEvenSix = new BigDecimal("1.246").setScale(2, RoundingMode.HALF_EVEN);
System.out.println("halfEvenOne:" + halfEvenOne);
System.out.println("halfEvenTwo:" + halfEvenTwo);
System.out.println("halfEvenThree:" + halfEvenThree);
System.out.println("halfEvenFour:" + halfEvenFour);
System.out.println("halfEvenFive:" + halfEvenFive);
System.out.println("halfEvenSix:" + halfEvenSix);

执行结果:

halfEvenOne:1.24
halfEvenTwo:1.22
halfEvenThree:1.24
halfEvenFour:1.24
halfEvenFive:1.24
halfEvenSix:1.25

符合预期。

RoundingMode.HALF_EVEN 验证:

BigDecimal unnecessaryOne = new BigDecimal("1.240").setScale(2, RoundingMode.UNNECESSARY);
System.out.println("unnecessaryOne:" + unnecessaryOne);
BigDecimal unnecessaryTwo = new BigDecimal("1.2401").setScale(2, RoundingMode.UNNECESSARY);
System.out.println("unnecessaryTwo:" + unnecessaryTwo);

执行结果:

unnecessaryOne:1.24
Exception in thread "main" java.lang.ArithmeticException: Rounding necessaryat java.math.BigDecimal.commonNeedIncrement(BigDecimal.java:4148)at java.math.BigDecimal.needIncrement(BigDecimal.java:4204)at java.math.BigDecimal.divideAndRound(BigDecimal.java:4112)at java.math.BigDecimal.setScale(BigDecimal.java:2452)at java.math.BigDecimal.setScale(BigDecimal.java:2386)at com.zt.dc.portal.admin.web.service.impl.satisfaction.SatisfactionEvaluationServiceImpl.main(SatisfactionEvaluationServiceImpl.java:262)

一个正常输出,一个抛出异常,符合预期。

总结:本文对 RoundingMode 共有 8 种舍位方式进行了详细分析验证,希望可以帮助到有需要的小伙伴。

欢迎提出建议及对错误的地方指出纠正。

这篇关于BigDecimal 小数位的处理(RoundingMode)的文章就介绍到这儿,希望我们推荐的文章对编程师们有所帮助!



http://www.chinasem.cn/article/1089065

相关文章

Java堆转储文件之1.6G大文件处理完整指南

《Java堆转储文件之1.6G大文件处理完整指南》堆转储文件是优化、分析内存消耗的重要工具,:本文主要介绍Java堆转储文件之1.6G大文件处理的相关资料,文中通过代码介绍的非常详细,需要的朋友可... 目录前言文件为什么这么大?如何处理这个文件?分析文件内容(推荐)删除文件(如果不需要)查看错误来源如何避

使用Python构建一个高效的日志处理系统

《使用Python构建一个高效的日志处理系统》这篇文章主要为大家详细讲解了如何使用Python开发一个专业的日志分析工具,能够自动化处理、分析和可视化各类日志文件,大幅提升运维效率,需要的可以了解下... 目录环境准备工具功能概述完整代码实现代码深度解析1. 类设计与初始化2. 日志解析核心逻辑3. 文件处

Java docx4j高效处理Word文档的实战指南

《Javadocx4j高效处理Word文档的实战指南》对于需要在Java应用程序中生成、修改或处理Word文档的开发者来说,docx4j是一个强大而专业的选择,下面我们就来看看docx4j的具体使用... 目录引言一、环境准备与基础配置1.1 Maven依赖配置1.2 初始化测试类二、增强版文档操作示例2.

MyBatis-Plus通用中等、大量数据分批查询和处理方法

《MyBatis-Plus通用中等、大量数据分批查询和处理方法》文章介绍MyBatis-Plus分页查询处理,通过函数式接口与Lambda表达式实现通用逻辑,方法抽象但功能强大,建议扩展分批处理及流式... 目录函数式接口获取分页数据接口数据处理接口通用逻辑工具类使用方法简单查询自定义查询方法总结函数式接口

SpringBoot结合Docker进行容器化处理指南

《SpringBoot结合Docker进行容器化处理指南》在当今快速发展的软件工程领域,SpringBoot和Docker已经成为现代Java开发者的必备工具,本文将深入讲解如何将一个SpringBo... 目录前言一、为什么选择 Spring Bootjavascript + docker1. 快速部署与

Python使用vllm处理多模态数据的预处理技巧

《Python使用vllm处理多模态数据的预处理技巧》本文深入探讨了在Python环境下使用vLLM处理多模态数据的预处理技巧,我们将从基础概念出发,详细讲解文本、图像、音频等多模态数据的预处理方法,... 目录1. 背景介绍1.1 目的和范围1.2 预期读者1.3 文档结构概述1.4 术语表1.4.1 核

Spring Boot @RestControllerAdvice全局异常处理最佳实践

《SpringBoot@RestControllerAdvice全局异常处理最佳实践》本文详解SpringBoot中通过@RestControllerAdvice实现全局异常处理,强调代码复用、统... 目录前言一、为什么要使用全局异常处理?二、核心注解解析1. @RestControllerAdvice2

电脑提示xlstat4.dll丢失怎么修复? xlstat4.dll文件丢失处理办法

《电脑提示xlstat4.dll丢失怎么修复?xlstat4.dll文件丢失处理办法》长时间使用电脑,大家多少都会遇到类似dll文件丢失的情况,不过,解决这一问题其实并不复杂,下面我们就来看看xls... 在Windows操作系统中,xlstat4.dll是一个重要的动态链接库文件,通常用于支持各种应用程序

SQL Server数据库死锁处理超详细攻略

《SQLServer数据库死锁处理超详细攻略》SQLServer作为主流数据库管理系统,在高并发场景下可能面临死锁问题,影响系统性能和稳定性,这篇文章主要给大家介绍了关于SQLServer数据库死... 目录一、引言二、查询 Sqlserver 中造成死锁的 SPID三、用内置函数查询执行信息1. sp_w

Java对异常的认识与异常的处理小结

《Java对异常的认识与异常的处理小结》Java程序在运行时可能出现的错误或非正常情况称为异常,下面给大家介绍Java对异常的认识与异常的处理,本文给大家介绍的非常详细,对大家的学习或工作具有一定的参... 目录一、认识异常与异常类型。二、异常的处理三、总结 一、认识异常与异常类型。(1)简单定义-什么是