New to Java

Hey, I've received an error message in my roman numeral program and am not what I'm doing wrong.

Here's the error:


C:\Documents and Settings\Mitch Thul\Desktop\Java2\lab5\Roman2.java:22: cannot find symbol
symbol : variable length
location: class java.lang.String
for(int i = 0; i <= roman.length - 2; i++)
^
C:\Documents and Settings\Mitch Thul\Desktop\Java2\lab5\Roman2.java:25: cannot find symbol
symbol : method charAt(int)
location: class Roman2
if((charAt(i)) >= (charAt(i+1)))
^
C:\Documents and Settings\Mitch Thul\Desktop\Java2\lab5\Roman2.java:25: cannot find symbol
symbol : method charAt(int)
location: class Roman2
if((charAt(i)) >= (charAt(i+1)))
^
3 errors

Tool completed with exit code 1


And here's my code:

//Mitch Thul 3059899

import java.util.Scanner;
import java.lang.String;

public class Roman2
{
	public static void main(String[] arg)
	{
		Scanner keyboard = new Scanner(System.in);
		String date;
		System.out.println("Please enter a roman numeral date:");
		date = keyboard.next();
		System.out.println("Roman numeral = " + date);
	}
		public static int romanToInt(String roman)
		{
			//takes a string of roman numerals (date) and produces corresponding int
			int n; //value of next numeral
			roman = roman + "0"; //adds 0 to the end of the numeral string (for simplification)
			int total = 0; //start at position 0
			for(int i = 0; i <= roman.length - 2; i++)
			{
				n = numeralToInt(roman.charAt(i));
				if((charAt(i)) >= (charAt(i+1)))
				{
					total += n; // add n to the total
				}
				else
				{
					total -= n; //subtract n from the total
				}
				return total;
			}
		}
		private static int numeralToInt(char ch)
		{
			switch(ch)
			{
				case 'M': return 1000;
				case 'D': return 500;
				case 'C': return 100;
				case 'L': return 50;
				case 'X': return 10;
				case 'V': return 5;
				case 'I': return 1;
				case '0': return 0;
			}
			return 0;
		}
}

Thanks in advance for any help.