1. Overview
1.概述
In this tutorial, we’ll see how we can convert a monetary amount into words-representation in Java.
在本教程中，我们将看到如何在Java中把一个货币金额转换为文字表述。
We’ll also see how a custom implementation could look like, via an external library – Tradukisto.
我们还将看到，通过一个外部库–Tradukisto，一个自定义的实现会是什么样子。
2. Implementation
2.实施
Let’s first start with our own implementation. The first step is to declare two String arrays with the following elements:
让我们首先从我们自己的实现开始。第一步是声明两个String数组，其元素如下。
public static String[] ones = {
"", "one", "two", "three", "four",
"five", "six", "seven", "eight",
"nine", "ten", "eleven", "twelve",
"thirteen", "fourteen", "fifteen",
"sixteen", "seventeen", "eighteen",
"nineteen"
};
public static String[] tens = {
"", // 0
"", // 1
"twenty", // 2
"thirty", // 3
"forty", // 4
"fifty", // 5
"sixty", // 6
"seventy", // 7
"eighty", // 8
"ninety" // 9
};When we receive an input, we’ll need to handle the invalid values (zero and negative values). Once a valid input is received, we can extract the number of dollars and cents into variables:
当我们收到一个输入时，我们需要处理无效的值（零和负值）。一旦收到一个有效的输入，我们就可以将美元和美分的数量提取到变量中：。
long dollars = (long) money;
long cents = Math.round((money - dollars) * 100);If the number given is less than 20, then we’ll get the appropriate ones’ element from the array based on the index:
如果给出的数字小于20，那么我们将根据索引从数组中获得适当的ones’元素。
if (n < 20) {
return ones[(int) n];
}We’ll use a similar approach for numbers less than 100, but now we have to use tens array as well:
我们将对小于100的数字使用类似的方法，但现在我们也必须使用tens array。
if (n < 100) {
return tens[(int) n / 10]
+ ((n % 10 != 0) ? " " : "")
+ ones[(int) n % 10];
}We do this similarly for numbers that are less than one thousand.
对于小于一千的数字，我们也是这样做的。
Next, we use recursive calls to deal with numbers that are less than one million, as shown below:
接下来，我们使用递归调用来处理小于一百万的数字，如下所示。
if (n < 1_000_000) {
return convert(n / 1000) + " thousand" + ((n % 1000 != 0) ? " " : "")
+ convert(n % 1000);
}The same approach is used for numbers that are less than one billion, and so on.
同样的方法也用于小于10亿的数字，以此类推。
Here is the main method that can be called to do this conversion:
这里是可以被调用来进行这种转换的主要方法。
public static String getMoneyIntoWords(double money) {
long dollars = (long) money;
long cents = Math.round((money - dollars) * 100);
if (money == 0D) {
return "";
}
if (money < 0) {
return INVALID_INPUT_GIVEN;
}
String dollarsPart = "";
if (dollars > 0) {
dollarsPart = convert(dollars)
+ " dollar"
+ (dollars == 1 ? "" : "s");
}
String centsPart = "";
if (cents > 0) {
if (dollarParts.length() > 0) {
centsPart = " and ";
}
centsPart += convert(cents) + " cent" + (cents == 1 ? "" : "s");
}
return dollarsPart + centsPart;
}Let’s test our code to make sure it works:
让我们测试一下我们的代码，以确保它能工作。
@Test
public void whenGivenDollarsAndCents_thenReturnWords() {
String expectedResult
= "nine hundred twenty four dollars and sixty cents";
assertEquals(
expectedResult,
NumberWordConverter.getMoneyIntoWords(924.6));
}
@Test
public void whenTwoBillionDollarsGiven_thenReturnWords() {
String expectedResult
= "two billion one hundred thirty three million two hundred"
+ " forty seven thousand eight hundred ten dollars";
assertEquals(
expectedResult,
NumberWordConverter.getMoneyIntoWords(2_133_247_810));
}
@Test
public void whenThirtyMillionDollarsGiven_thenReturnWords() {
String expectedResult
= "thirty three million three hundred forty eight thousand nine hundred seventy eight dollars";
assertEquals(
expectedResult,
NumberWordConverter.getMoneyIntoWords(33_348_978));
}Let’s also test some edge cases, and make sure we have covered them as well:
让我们也测试一些边缘案例，并确保我们也已经涵盖了这些案例。
@Test
public void whenZeroDollarsGiven_thenReturnEmptyString() {
assertEquals("", NumberWordConverter.getMoneyIntoWords(0));
}
@Test
public void whenNoDollarsAndNineFiveNineCents_thenCorrectRounding() {
assertEquals(
"ninety six cents",
NumberWordConverter.getMoneyIntoWords(0.959));
}
@Test
public void whenNoDollarsAndOneCent_thenReturnCentSingular() {
assertEquals(
"one cent",
NumberWordConverter.getMoneyIntoWords(0.01));
}
3. Using a Library
3.使用一个库
Now that we’ve implemented our own algorithm, let’s do this conversion by using an existing library.
现在我们已经实现了自己的算法，让我们通过使用一个现有的库来进行这种转换。
Tradukisto is a library for Java 8+, which can help us convert numbers to their word representations. First, we need to import it into our project (the latest version of this library can be found here):
Tradukisto是一个适用于Java 8+的库，它可以帮助我们将数字转换为其文字表示。首先，我们需要将其导入我们的项目中（该库的最新版本可以在这里）。
<dependency>
<groupId>pl.allegro.finance</groupId>
<artifactId>tradukisto</artifactId>
<version>1.0.1</version>
</dependency>We can now use MoneyConverters‘s asWords() method to do this conversion:
我们现在可以使用MoneyConverters的asWords()方法来做这个转换。
public String getMoneyIntoWords(String input) {
MoneyConverters converter = MoneyConverters.ENGLISH_BANKING_MONEY_VALUE;
return converter.asWords(new BigDecimal(input));
}Let’s test this method with a simple test case:
让我们用一个简单的测试案例来测试这个方法。
@Test
public void whenGivenDollarsAndCents_thenReturnWordsVersionTwo() {
assertEquals(
"three hundred ten £ 00/100",
NumberWordConverter.getMoneyIntoWords("310"));
}We could also use the ICU4J library to do this, but it’s a large one and comes with many other features that are out of the scope of this article.
我们也可以使用ICU4J库来做到这一点，但它是一个很大的库，并且带有许多其他功能，不在本文的范围之内。
However, have a look at it if Unicode and globalization support is needed.
然而，如果需要Unicode和全球化支持，请看一下它。
4. Conclusion
4.结论
In this quick article, we saw two approaches on how to do the conversion of a sum of money into words.
在这篇快速文章中，我们看到了两种关于如何将一笔钱转换为文字的方法。
The code for all the examples explained here, and much more can be found over on GitHub.
这里解释的所有例子的代码，以及更多的代码可以在GitHub上找到。