NumberConverter

NumberConverter implemented for recruitment process in Comarch company.

What do you need?

The only things which you need to run this project is to have:

Java 8,
Maven (working mvn command in terminal),
Working internet connection,
Free 4567 port.

How to run it?

Simple as that:

Download zipped project from Github (or git clone https://github.com/pitagoras3/number_converter.git),
Open root project folder in terminal,
Run mvn exec:java

Or... Just run main(String[] args) function placed in API class in your IDE.

How to use it?

You can use your internet browser or Postman to use this REST API.

URL wich evaluates conversion function is available on:

http://localhost:4567/convert/METHOD/NUMBER_TO_CONVERT

Methods:

hex
roman

Number to convert must be positive integer.

Examples of usage

http://localhost:4567/convert/hex/123

http://localhost:4567/convert/roman/1

Errors

If user will provide wrong data, he will receive error describing what's wrong.

404 Not Found - Something is wrong with URL,
No such method error. - User provided method which is not hex || roman,
Not a number error. - User provided not a number into number parameter.
Not positive number error. - User provided neg

What I've used to make NumberConverter?

For API development I've used Spark library: Spark documentation.

Conversion to roman system

Conversion to roman system is made using changed and repaired method from this Gist: julienhaversano/Converter.java.

In this solution I've changed iteration over array from this:

for (int i : NUMBER_VALUES) { // loop through all the values
            while (num >= NUMBER_VALUES[i]) { // Check if the number is greater than the current value
                roman += NUMBER_LETTERS[i]; // Add the letter to the String
                num -= NUMBER_VALUES[i]; // Subtract the amount from the value
            }
        }

Which caused ArrayIndexOutOfBoundsException (because it took value from array, not the index), into this:

StringBuilder romanNumberBuilder = new StringBuilder();
        for (int i = 0; i < ARABIC_VALUES.length; i++) {
            while (numberToConvert >= ARABIC_VALUES[i]) {
                romanNumberBuilder.append(ROMAN_VALUES[i]);
                numberToConvert -= ARABIC_VALUES[i];
            }
        }

As you can see I've also added StringBuilder instead of concatenating String inside loop with += (which is generally a bad practice).

Unit tests

As part of exercise I wrote unit tests for project. There are two @Test classes in project:

APITest
ConverterTest

APITest tests connection with API by sending different requests - it is necessary to have running API during this test (in other case test methods inside this class will mostly fail).

ConverterTest class can work without running API - it tests backend methods which are responsible for conversion to specific numeral systems.

pitagoras3/number_converter