RomanNumbers (josef 3.2.5 API)

java.lang.Object
- org.josef.science.math.RomanNumbers

```
@Status(stage=PRODUCTION,
        unitTests=COMPLETE)
 @Review(by="Kees Schotanus",
        at="2009-09-28")
 @ThreadSafety(level=IMMUTABLE,
              doc="Utility class with static methods only")
public final class RomanNumbers
extends Object
```
Utility class for the conversion of Roman numbers to Arabic numbers and vice versa.
Romans used the following numerals with corresponding values to make Roman numbers:
I=1, V=5, X=10, L=50, C=100, D=500, M=1000.
All Roman numbers should conform to the following rules:
1 ) Roman numbers should be read and written from left to right.
2 ) Numerals with a value equal to a power of ten may be repeated up to three times.
3 ) Numerals with a value unequal to a power of ten may occur only once.
4 ) Unless all the conditions under sub 5 are met, numerals with a lower value follow numerals with higher values. Conversion to Arabic numbers in this case is simple, just add the value of all Roman numbers.
5 ) Succeeding a numeral x, with a numeral y with a higher value than the value of x is legal when all of the conditions under 5a/5d are met.
Conversion to Arabic is easy, just subtract the value of x from y. Example: IX => 10 - 1 = 9.
5a) The value of x must be a power of ten (I, X, C, M).
5b) The value of x must be 1/5 or 1/10 the value of y.
5c) If another numeral z follows numeral y, then the value of z must be smaller than the value of x.
5d) x must either be the first numeral in the expression, or x must be preceded by a numeral of at least ten times the value of x.

The following Roman numbers are illegal.
IIX Violates rule 5d, use VIII to specify 8
VM Violates rules 5a and 5b, use CMXCV to specify 995
LXL Violates rules 3 and 5b, use XC to specify 90

Version:

1.0 $Revision: 6488 $

Author:

Kees Schotanus

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`C` Arabic value of the Roman number C.
`static int`	`D` Arabic value of the Roman number D.
`static int`	`I` Arabic value of the Roman number I.
`static int`	`L` Arabic value of the Roman number L.
`static int`	`LARGEST_ROMAN_NUMBER` The largest number the Romans could represent.
`static int`	`M` Arabic value of the Roman number M.
`static int`	`V` Arabic value of the Roman number V.
`static int`	`X` Arabic value of the Roman number X.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static int`	`getValue(char romanNumeral)` Gets the value of one Roman numeral.
`static boolean`	`isValid(String romanNumber)` Determines whether a Roman number is a valid Roman number or not.
`static void`	`main(String[] args)` Tests the above functionality.
`static int`	`toArabic(String number)` Converts a Roman number to an Arabic number.
`static String`	`toRoman(int number)` Converts an Arabic number to a Roman number.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LARGEST_ROMAN_NUMBER
```
public static final int LARGEST_ROMAN_NUMBER
```
    The largest number the Romans could represent.
    
    See Also:
    
    Constant Field Values
  - I
```
public static final int I
```
    Arabic value of the Roman number I.
    
    See Also:
    
    Constant Field Values
  - V
```
public static final int V
```
    Arabic value of the Roman number V.
    
    See Also:
    
    Constant Field Values
  - X
```
public static final int X
```
    Arabic value of the Roman number X.
    
    See Also:
    
    Constant Field Values
  - L
```
public static final int L
```
    Arabic value of the Roman number L.
    
    See Also:
    
    Constant Field Values
  - C
```
public static final int C
```
    Arabic value of the Roman number C.
    
    See Also:
    
    Constant Field Values
  - D
```
public static final int D
```
    Arabic value of the Roman number D.
    
    See Also:
    
    Constant Field Values
  - M
```
public static final int M
```
    Arabic value of the Roman number M.
    
    See Also:
    
    Constant Field Values
- Method Detail
  - toRoman
```
public static String toRoman(int number)
```
    Converts an Arabic number to a Roman number.
    Converting from Arabic to Roman is simply a matter of looking up and concatenating the Roman numerals for each Arabic digit.
    
    Parameters:
    
    number - Arabic number to convert.
    
    Returns:
    
    Roman number.
    
    Throws:
    
    IllegalArgumentException - When the Arabic number is not in the range: 0 <= number <= LARGEST_ROMAN_NUMBER.
  - toArabic
```
public static int toArabic(String number)
```
    Converts a Roman number to an Arabic number.
    Conversion from Roman to Arabic is simple, just add the value of each Roman numeral to the result. There is one exception to this rule: if the value of the current Roman numeral is less than the value of the next Roman numeral, than the value of the current Roman numeral should be subtracted from the result.
    
    Parameters:
    
    number - Roman number to convert.
    
    Returns:
    
    Arabic number.
    
    Throws:
    
    IllegalArgumentException - When the Roman number contains numerals that are not legal Roman numerals.
    
    NullPointerException - When the supplied number is null.
  - isValid
```
public static boolean isValid(String romanNumber)
```
    Determines whether a Roman number is a valid Roman number or not.
    Checking whether a Roman number is valid or not can be quite tedious when you look at all the rules a Roman number should adhere to. Fortunately there is an easy way which automatically takes all these rules into account. The trick used is the following:
    Convert the supplied Roman number to an Arabic number, then convert this number back into a Roman number and check this result against the supplied Roman number. If the values match a legal Roman number was supplied!
    
    Parameters:
    
    romanNumber - Valid or invalid Roman number.
    
    Returns:
    
    True when the supplied Roman number is valid, false otherwise.
    
    Throws:
    
    NullPointerException - When the supplied romanNumber is null.
  - getValue
```
public static int getValue(char romanNumeral)
```
    Gets the value of one Roman numeral.
    Note that this method is case sensitive.
    
    Parameters:
    
    romanNumeral - Roman numeral.
    
    Returns:
    
    Value (Arabic) of supplied Roman numeral.
    
    Throws:
    
    IllegalArgumentException - When the supplied Roman numeral is not a valid Roman numeral.
  - main
```
public static void main(String[] args)
```
    Tests the above functionality.
    Usage: RomanNumbers [Arabic_number|Roman_number]
    
    Parameters:
    
    args - Exactly one argument should be supplied. It should either be an Arabic number or a Roman number. The supplied parameter is converted and the result will be displayed.

Class RomanNumbers

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LARGEST_ROMAN_NUMBER

I

V

X

L

C

D

M

Method Detail

toRoman

toArabic

isValid

getValue

main