在Java中应该使用什么数据类型来表示钱?
当前回答
您可以使用Money and Currency API (JSR 354)。只要向项目添加适当的依赖项,就可以在中使用此API。
对于Java 8,将以下参考实现作为依赖项添加到pom.xml中:
<dependency>
<groupId>org.javamoney</groupId>
<artifactId>moneta</artifactId>
<version>1.0</version>
</dependency>
此依赖项将传递地添加javax。Money:作为依赖项的Money -api。
然后你可以使用API:
package com.example.money;
import static org.junit.Assert.assertThat;
import static org.hamcrest.CoreMatchers.is;
import java.util.Locale;
import javax.money.Monetary;
import javax.money.MonetaryAmount;
import javax.money.MonetaryRounding;
import javax.money.format.MonetaryAmountFormat;
import javax.money.format.MonetaryFormats;
import org.junit.Test;
public class MoneyTest {
@Test
public void testMoneyApi() {
MonetaryAmount eurAmount1 = Monetary.getDefaultAmountFactory().setNumber(1.1111).setCurrency("EUR").create();
MonetaryAmount eurAmount2 = Monetary.getDefaultAmountFactory().setNumber(1.1141).setCurrency("EUR").create();
MonetaryAmount eurAmount3 = eurAmount1.add(eurAmount2);
assertThat(eurAmount3.toString(), is("EUR 2.2252"));
MonetaryRounding defaultRounding = Monetary.getDefaultRounding();
MonetaryAmount eurAmount4 = eurAmount3.with(defaultRounding);
assertThat(eurAmount4.toString(), is("EUR 2.23"));
MonetaryAmountFormat germanFormat = MonetaryFormats.getAmountFormat(Locale.GERMAN);
assertThat(germanFormat.format(eurAmount4), is("EUR 2,23") );
}
}
其他回答
JSR 354:货币和货币API
JSR 354提供了一个API,用于表示、传输和执行Money和Currency的综合计算。你可以从以下连结下载:
JSR 354:货币和货币API下载
该规范包括以下内容:
用于处理例如货币数量和货币的API 支持可互换实现的api 用于创建实现类实例的工厂 用于计算、转换和格式化货币金额的功能 用于处理Money和Currencies的Java API,计划包含在Java 9中。 所有规范类和接口都位于javax.money中。*包。
JSR 354: Money and Currency API示例:
创建一个moneyaryamount并将其打印到控制台的示例如下:
MonetaryAmountFactory<?> amountFactory = Monetary.getDefaultAmountFactory();
MonetaryAmount monetaryAmount = amountFactory.setCurrency(Monetary.getCurrency("EUR")).setNumber(12345.67).create();
MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.getDefault());
System.out.println(format.format(monetaryAmount));
当使用参考实现API时,必要的代码要简单得多:
MonetaryAmount monetaryAmount = Money.of(12345.67, "EUR");
MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.getDefault());
System.out.println(format.format(monetaryAmount));
该API还支持monetaryamount的计算:
MonetaryAmount monetaryAmount = Money.of(12345.67, "EUR");
MonetaryAmount otherMonetaryAmount = monetaryAmount.divide(2).add(Money.of(5, "EUR"));
CurrencyUnit和moneyaryamount
// getting CurrencyUnits by locale
CurrencyUnit yen = MonetaryCurrencies.getCurrency(Locale.JAPAN);
CurrencyUnit canadianDollar = MonetaryCurrencies.getCurrency(Locale.CANADA);
moneyaryamount有各种方法,允许访问指定的货币,数字金额,其精度和更多:
MonetaryAmount monetaryAmount = Money.of(123.45, euro);
CurrencyUnit currency = monetaryAmount.getCurrency();
NumberValue numberValue = monetaryAmount.getNumber();
int intValue = numberValue.intValue(); // 123
double doubleValue = numberValue.doubleValue(); // 123.45
long fractionDenominator = numberValue.getAmountFractionDenominator(); // 100
long fractionNumerator = numberValue.getAmountFractionNumerator(); // 45
int precision = numberValue.getPrecision(); // 5
// NumberValue extends java.lang.Number.
// So we assign numberValue to a variable of type Number
Number number = numberValue;
monearyamount可以使用舍入运算符进行舍入:
CurrencyUnit usd = MonetaryCurrencies.getCurrency("USD");
MonetaryAmount dollars = Money.of(12.34567, usd);
MonetaryOperator roundingOperator = MonetaryRoundings.getRounding(usd);
MonetaryAmount roundedDollars = dollars.with(roundingOperator); // USD 12.35
当使用monearyamount的集合时,可以使用一些不错的实用程序方法进行过滤、排序和分组。
List<MonetaryAmount> amounts = new ArrayList<>();
amounts.add(Money.of(2, "EUR"));
amounts.add(Money.of(42, "USD"));
amounts.add(Money.of(7, "USD"));
amounts.add(Money.of(13.37, "JPY"));
amounts.add(Money.of(18, "USD"));
自定义monearyamount操作
// A monetary operator that returns 10% of the input MonetaryAmount
// Implemented using Java 8 Lambdas
MonetaryOperator tenPercentOperator = (MonetaryAmount amount) -> {
BigDecimal baseAmount = amount.getNumber().numberValue(BigDecimal.class);
BigDecimal tenPercent = baseAmount.multiply(new BigDecimal("0.1"));
return Money.of(tenPercent, amount.getCurrency());
};
MonetaryAmount dollars = Money.of(12.34567, "USD");
// apply tenPercentOperator to MonetaryAmount
MonetaryAmount tenPercentDollars = dollars.with(tenPercentOperator); // USD 1.234567
资源:
使用JSR 354在Java中处理金钱和货币
Java 9货币和货币API (JSR 354)
参见:JSR 354 -货币和货币
BigDecimal可以使用,为什么不使用Float或Double可以在这里看到:为什么不使用Double或Float来表示货币?
我会用Joda Money
它仍然是0.6版本,但看起来很有前途
对于简单的情况(一种货币),它是足够的int/long。 钱的单位是美分(…)或百分之一/千分之一美分(任何你需要的固定分割器精度)
BigDecimal是用于货币的最佳数据类型。
货币有很多容器,但它们都使用BigDecimal作为底层数据类型。使用BigDecimal不会出错,可能会使用BigDecimal。ROUND_HALF_EVEN舍入。