This application converts a input number to its equivalent in English words.
-Java version 8
-Spring boot, mvc.
-Junit v5
-Lombok
-spring-boot-starter-web
-maven
-Docker
-Swagger
-In this application, we do not need any database connectivity.
I pushed my changes always to the main branch because I was the only developer working in this Project, in another scenario with multiple developers, we have to follow a branch strategy, with the different branches for development and master ones, with different conventions such as /feature, /fix, /hotfix etc.
The maximum and minimum allowed values are -9223372036854775808 and 9223372036854775807, equivalent to the maximum and minimum Long Java values allowed.
To handle the input bad format error this app is using a @ControllerAdvice annotation in the ExceptionHandler class. This annotation allow us to get and handle all the exceptions in the app, in this case is important to handle the 400 badRequest which is sent when the number is higher than the allowed one or we receive a character as input.
I also added a custom NumbersToWordsException which extends from Exception to handle the application exceptions. It is not used because of the nature of the application, the only exception I handling is the bad request one for bad inputs according to the expressed above.
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As general explanation the number has different mapping units for division and as mapper words, trillions billions and so far and so for.
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The program starts in the convertNumberToWords method. First divide the initial number by mapper units (billions, millions, thousands, hundreds) and after each simple division calculate the remainder of the current number to get the next number in the sequence, for example with 12417, we calculate the remainder number
12417 % 1000 = 417with have12in the thousands variable and417as remainder. this417will be the next input in the sequence to be converted, after 12and will be divided by the hundred mapper and so far and so for. -
12 is the current program input to be mapped to words. In this case we just will have tens and units to convert. 12 will be mapped to twelve + thousand and continue with the next mapper.
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417 will be the Divide by Hundred (417/100 = 4), the result is 4 Hundrer in its mapping.
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Again, calculate the remainder number. 417 % 100 = 17, and 17 4 is found on NUMBERS_UP_TO_19 array. So, return
Seventeen, in this case the convertTensAndUnits method. For this case we append anandseparator. each time we have ten units.
7)Finally, the function capitalizeWords formats the final input and will return “Twelve thousand four hundred and seventeen”.
In the case of negative numbers the program appends a negative word at the begin of the final translate number, using the isNegativeNumber flag variable.
I covered different business cases in the NumbersToWordsConverterTest class according to the constraints of the application The final code coverage percentage for all the application is the next:
To run it locally you must follow these three steps:
Clone the app and in the terminal go to the root directory with the command: cd conversion-numbers-to-words.
In the terminal, located in the root directory (conversion-numbers-to-words) run mvn clean install
Make sure that the .jar file was generated in the target directory:
In the same directory, run the command docker build -t numbers-conversion-to-words:1.0 . to create the APP image.
Make sure that the image was created with the docker images command:
Then in the same terminal run the command: docker run -p 8080:8080 numbers-conversion-to-words:1.0 to run the app in local in the 8080 port.
http://localhost:8080/swagger-ui.html#/numbers-to-words-controller
I tested in postman the big negative number allowed by the Long type (-9223372036854775808).
