(question is at the bottom after the code)

import javax.swing.JOptionPane;

public class RomanNumerals {

public static void main(String[] args) {

// TODO Auto-generated method stub

final String title =("Conversion of Roman numerals");

final String task =("Enter a Roman numeral between \"I\" and \"XV\"");

String roman=JOptionPane.showInputDialog(null,task,title,JOptionPane.QUESTION_MESSAGE);

char firstCharacter=roman.charAt(0);

char secondCharacter=roman.charAt(1);

char thirdCharacter=roman.charAt(2);

char fourthCharacter=roman.charAt(3);

int decimal;

if (firstCharacter !=('I')||firstCharacter!=('i')||firstCharacter!=('V')||firstCharacter!=('v')||firstCharacter!=('X')||firstCharacter!=('x'))

JOptionPane.showMessageDialog(null, "Please input a valid roman numeral from I to XV.");

if (firstCharacter ==('I') || firstCharacter==('i'))

{if (secondCharacter==('I')||secondCharacter==('i'))

{if (thirdCharacter==('I')||thirdCharacter==('i'))

decimal = 3;}

else if (secondCharacter==('V')||secondCharacter==('v'))

decimal = 4;

else if (secondCharacter==('X')||secondCharacter==('x'))

decimal = 9;

decimal = 2;}

decimal = 1;

if (firstCharacter==('V') || firstCharacter==('v'))

{if (secondCharacter==('I')||secondCharacter==('i'))

{if (thirdCharacter==('I')||thirdCharacter==('i'))

{if (fourthCharacter==('I')||fourthCharacter==('i'))

decimal = 8;}

decimal = 7;}

decimal = 6;}

decimal = 5;

if (firstCharacter==('X')||firstCharacter==('x'))

{if (secondCharacter==('I')||secondCharacter==('i'))

{if (thirdCharacter==('I')||thirdCharacter==('i'))

{if (fourthCharacter==('I')||fourthCharacter==('i'))

decimal = 13;}

else if (thirdCharacter==('V')||thirdCharacter==('v'))

decimal = 14;

decimal = 12;}

else if (secondCharacter==('V')||secondCharacter==('v'))

decimal = 15;

decimal = 11;}

decimal = 10;

JOptionPane.showMessageDialog(null, "The decimal value for the Roman numeral "+roman+" is: ........"+decimal+ "........",title,JOptionPane.INFORMATION_MESSAGE);

//program terminates without displaying JOptionPane showing the decimal value

//not sure what i did wrong because this makes sense to me but obviously there's something im not understanding

//i refuse to put any more thought into this waist of time, this is my best attempt at it

// originally tried using else if in the code but it kept flagging it as an error

System.exit(0);}

}

My question is, what am I doing wrong? For this assignment we have to use if-else statements, that's why this is so much longer than it needs to be. Probably don't need me to tell you but this is with java eclipse. please help