Converter of Arabic numbers to Roman numbers

RomanNumeral.java

import java.util.HashMap;
import java.util.Map;

public class RomanNumeral
{

  private static final Map<Integer, String[]> romanCharsByDecimalPlace = new HashMap<Integer, String[]>()
	{
		{
			put( 0, new String[]
					{
							"I", "V", "X"
					}
			);

			put( 1, new String[]
					{
							"X", "L", "C"
					}
			);

			put( 2, new String[]
					{
							"C", "D", "M"
					}
			);
		}
	};

	public static String convert( int number )
	{
		String nStr = Integer.toString( number );
		char[] parts = nStr.toCharArray();
		String result = "";
		for( int i = parts.length - 1; i >= 0; i-- )
		{
			result += convertDigit( Character.getNumericValue( parts[parts.length - i - 1] ), i );
		}
		return result;
	}

	public static String convertDigit( int digit, int decimalPlace )
	{
		if( digit <= 0 )
		{
			return "";
		}
		if( digit <= 3 )
		{
			return times( digit, romanCharsByDecimalPlace.get( decimalPlace )[0] );
		}
		else if( digit == 4 )
		{
			return romanCharsByDecimalPlace.get( decimalPlace )[0] +
					romanCharsByDecimalPlace.get( decimalPlace )[1];
		}
		else if( digit <= 8 )
		{
			return romanCharsByDecimalPlace.get( decimalPlace )[1] +
					times( digit - 5, romanCharsByDecimalPlace.get( decimalPlace )[0] );
		}
		else
		{
			return romanCharsByDecimalPlace.get( decimalPlace )[0] +
					romanCharsByDecimalPlace.get( decimalPlace )[2];
		}
	}

	private static String times( int factor, String text )
	{
		String res = "";
		for( int i = 0; i < factor; i++ )
		{
			res += text;
		}
		return res;
	}


}

RomanNumeralTest.java

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.*;

import java.util.Arrays;
import java.util.Collection;

import static junit.framework.Assert.assertEquals;

@RunWith( Parameterized.class )
public class RomanNumeralTest
{
  private int number;
	private String romanNumber;

	public RomanNumeralTest( int number, String romanNumber )
	{
		this.number = number;
		this.romanNumber = romanNumber;
	}

	@Parameters
	public static Collection<Object[]> bunchOfPrimes()
	{
		return Arrays.asList( new Object[][]
				{
						{ 1, "I" },
						{ 2, "II" },
						{ 3, "III" },
						{ 4, "IV" },
						{ 5, "V" },
						{ 6, "VI" },
						{ 7, "VII" },
						{ 8, "VIII" },
						{ 9, "IX" },
						{ 10, "X" },
						{ 11, "XI" },
						{ 13, "XIII" },
						{ 14, "XIV" },
						{ 15, "XV" },
						{ 18, "XVIII" },
						{ 20, "XX" },
						{ 30, "XXX" },
						{ 90, "XC" },
						{ 100, "C" },
						{ 101, "CI" },
				} );
	}

	@Test
	public void testConvert()
	{
		assertEquals( romanNumber, RomanNumeral.convert( number ) );
	}

	/*
	@Test
	public void oneShouldBeI()
	{
		assertEquals( "I", RomanNumeral.convert( 1 ) );
	}

	@Test
	public void twoShouldBeII()
	{
		assertEquals( "II", RomanNumeral.convert( 2 ) );
	}

	@Test
	public void fiveShouldBeV()
	{
		assertEquals( "V", RomanNumeral.convert( 5 ) );
	}
	*/
}