guicassolato / n2w

Java library to convert numbers to words

n2w

This a simple Java library to convert numbers to English words, such as "1005" is converted to "one thousand and five". It was originally presented as a solution to a public Java coding challenge from a company in the UK.

Original Problem Description

Create a Java library, suitable for use in a server-side application, that can take a Java int in the range 0 to 999,999,999 inclusive and returns the equivalent number, as a String, in British English words.

Sample Data

Input	Output
0	zero
1	one
21	twenty one
105	one hundred and five
123	one hundred and twenty three
1005	one thousand and five
1042	one thousand and forty two
1105	one thousand one hundred and five
56945781	fifty six million nine hundred and forty five thousand seven hundred and eighty one
999999999	nine hundred and ninety nine million nine hundred and ninety nine thousand nine hundred and ninety nine.

Guidelines

• The solution must be correct. Please pay attention to the specific conventions of British English, particularly concerning the use of ‘and’ between certain phrases.
• The solution is not expected to involve a command line or GUI application – we’re looking for an object-oriented Java library that could be packaged as a jar and used in a larger application.
• The solution should not make use of external libraries other than for testing purposes.
• The solution should demonstrate a candidate’s abilities as a software engineer including, for example, TDD principles, general object-oriented principles and domain modeling principles.
• Please submit a solution that captures the business domain for the problem

Test

The project includes a JUnit class NumberToWordTest. Use it to test against all sample data above and a few others.

License

Although the company that has originally presented the challenge hasn't really registered it under any public license that we know, it seems reasonable to always give the credits. The challenge itself was created by Worldpay UK. This one solution should be credit to Guilherme Cassolato and is licensed under the MIT License.

Support

No support will be provided. Use it at your own risk. But if you need to get in touch for any other reason or you have significant improvement advices to share, please open an issue and I promise I'll try to respond it as soon as possible.