Java应用程序中用于赚钱的最佳数据类型是什么？

Question

Java应用程序中用于资金的最佳数据类型是什么？

Answer 1

Java具有Currency代表ISO 4217货币代码的类. BigDecimal是表示货币十进制值的最佳类型.

Joda Money提供了一个代表金钱的图书馆.

Answer 2

您可以使用Money和Currency API(JSR 354).此API有望成为Java 9的一部分.只要向项目添加适当的依赖项,就可以在Java 7和Java 8中使用此API.

对于Java 8,将以下引用实现添加为您的依赖项pom.xml:

<dependency>
    <groupId>org.javamoney</groupId>
    <artifactId>moneta</artifactId>
    <version>1.0</version>
</dependency>

此依赖项将javax.money:money-api作为依赖项传递添加.

然后,您可以使用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") );
    }
}

Answer 3

表示可能的最小值的整数类型.换句话说,你的程序应该用美分/欧元来思考.

这不应该阻止你把gui翻译成美元/欧元.

Answer 4

可以使用BigDecimal,在这里可以看到为什么不使用Float或Double的很好解释:为什么不使用Double或Float来表示货币？

Answer 5

JSR 354:货币和货币API

JSR 354提供了一个API,用于使用货币和货币表示,传输和执行综合计算.您可以从以下链接下载:

JSR 354:货币和货币API下载

该规范包括以下内容:

1. 用于处理货币金额和货币的API
2. 用于支持可互换实现的API
3. 用于创建实现类实例的工厂
4. 用于计算,转换和格式化货币金额的功能
5. 用于处理货币和货币的Java API,计划包含在Java 9中.
6. 所有规范类和接口都位于javax.money.*包中.

JSR 354示例:Money和Currency API:

创建MonetaryAmount并将其打印到控制台的示例如下所示::

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));

使用参考实现API时,必要的代码更简单:

MonetaryAmount monetaryAmount = Money.of(12345.67, "EUR");
MonetaryAmountFormat format = MonetaryFormats.getAmountFormat(Locale.getDefault());
System.out.println(format.format(monetaryAmount));

API还支持使用MonetaryAmounts进行计算:

MonetaryAmount monetaryAmount = Money.of(12345.67, "EUR");
MonetaryAmount otherMonetaryAmount = monetaryAmount.divide(2).add(Money.of(5, "EUR"));

CurrencyUnit和MonetaryAmount

// getting CurrencyUnits by locale
CurrencyUnit yen = MonetaryCurrencies.getCurrency(Locale.JAPAN);
CurrencyUnit canadianDollar = MonetaryCurrencies.getCurrency(Locale.CANADA);

MonetaryAmount有多种方法可以访问指定的货币,数量,精度等等:

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;

可以使用舍入运算符舍入MonetaryAmounts:

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

使用MonetaryAmounts集合时,可以使用一些很好的过滤,排序和分组实用方法.

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MonetaryAmount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处理Java中的货币和货币

研究Java 9货币和货币API(JSR 354)

另见:JSR 354 - 货币和货币

Answer 6

我会用Joda Money

它仍处于0.6版本,但看起来非常有前景

Answer 7

您应该使用BigDecimal 来表示货币值。它允许您使用各种舍入模式，在金融应用中，舍入模式通常是一个硬要求，甚至可能是法律规定的。

Answer 8

我已经做了一个微基准测试(JMH)来比较Moneta(java货币JSR 354实现)与BigDecimal的性能.

令人惊讶的是,BigDecimal性能似乎比moneta更好.我使用了以下moneta配置:

org.javamoney.moneta.Money.defaults.precision = 19 org.javamoney.moneta.Money.defaults.roundingMode = HALF_UP

package com.despegar.bookedia.money;

import org.javamoney.moneta.FastMoney;
import org.javamoney.moneta.Money;
import org.openjdk.jmh.annotations.*;

import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;
import java.util.concurrent.TimeUnit;

@Measurement(batchSize = 5000, iterations = 10, time = 2, timeUnit =     TimeUnit.SECONDS)
@Warmup(iterations = 2)
@Threads(value = 1)
@Fork(value = 1)
@State(Scope.Benchmark)
@BenchmarkMode(Mode.Throughput)
public class BigDecimalBenchmark {

private static final Money MONEY_BASE = Money.of(1234567.3444, "EUR");
private static final Money MONEY_SUBSTRACT = Money.of(232323, "EUR");
private static final FastMoney FAST_MONEY_SUBSTRACT = FastMoney.of(232323, "EUR");
private static final FastMoney FAST_MONEY_BASE = FastMoney.of(1234567.3444, "EUR");
MathContext mc = new MathContext(10, RoundingMode.HALF_UP);

@Benchmark
public void bigdecimal_string() {
    new BigDecimal("1234567.3444").subtract(new BigDecimal("232323")).multiply(new BigDecimal("3.4"), mc).divide(new BigDecimal("5.456"), mc);
}

@Benchmark
public void bigdecimal_valueOf() {
    BigDecimal.valueOf(12345673444L, 4).subtract(BigDecimal.valueOf(232323L)).multiply(BigDecimal.valueOf(34, 1), mc).divide(BigDecimal.valueOf(5456, 3), mc);
}
@Benchmark
public void fastmoney() {
    FastMoney.of(1234567.3444, "EUR").subtract(FastMoney.of(232323, "EUR")).multiply(3.4).divide(5.456);
}

@Benchmark
public void money() {
    Money.of(1234567.3444, "EUR").subtract(Money.of(232323, "EUR")).multiply(3.4).divide(5.456);
}

@Benchmark
public void money_static(){
    MONEY_BASE.subtract(MONEY_SUBSTRACT).multiply(3.4).divide(5.456);
}

@Benchmark
public void fastmoney_static() {
    FAST_MONEY_BASE.subtract(FAST_MONEY_SUBSTRACT).multiply(3.4).divide(5.456);
    }
}

导致

Benchmark                                Mode  Cnt     Score    Error  Units
BigDecimalBenchmark.bigdecimal_string   thrpt   10   479.465 ± 26.821  ops/s
BigDecimalBenchmark.bigdecimal_valueOf  thrpt   10  1066.754 ± 40.997  ops/s
BigDecimalBenchmark.fastmoney           thrpt   10    83.917 ±  4.612  ops/s
BigDecimalBenchmark.fastmoney_static    thrpt   10   504.676 ± 21.642  ops/s
BigDecimalBenchmark.money               thrpt   10    59.897 ±  3.061  ops/s
BigDecimalBenchmark.money_static        thrpt   10   184.767 ±  7.017  ops/s

如果我错过了什么,请随时纠正我

Answer 9

对于简单的情况（一种货币），它就足够了int/ long。以美分（...）或百分之一/千分之一（固定分频器所需的任何精度）为单位