Using the char data type.

char is basically in integer, but instead of showing the number, it prints what is displayed using the ACSII table of characters.
So char 'A' is actually the number 65 and it displays as A.

Also note that chars are SINGLE characters (letters, numbers, punctuation) and are always in ' '. So 'Hi' is invalid since it is more than one letter.

Conversions from char to int and vice versa

public class CharStuff {

	public static void main(String[] args) {
		
		//1. int to char : cast  (A == 65, a == 97)
		int n = 66;
		char cc = (char)n;
		//System.out.println(n + "   -> '" + cc + "'"); 	//let's switch to printf to make it look nicer
		System.out.printf(" %2d -> '%c'%n",n,cc);
		
		//2. char to int : Just do it!
		cc = 'E';
		n = cc;
//		System.out.println("'" + cc +"' -> " + n);
		System.out.printf(" '%c'-> %2d%n",cc,n);
		
		//3. Make 1=A, 2=B : add A-1 (because we don't want A to be zero)
		n = 4; //change to D and d
		
		cc = (char) (n + 'A' -1);
		System.out.printf(" %2d -> '%c'%n",n,cc);
		cc = (char) (n + 'a' -1);
		System.out.printf(" %2d -> '%c'%n",n,cc);
		
		//4. Change A to 1, B to 2 ... : opposite of above
		cc = 'J';
		n = cc - 'A' +1; // should be 10
		System.out.printf(" '%c'-> %2d%n",cc,n);
		
		//5. Change int digit to char digit : add the value of '0' ('0'==48)
		n = 3;
		cc = (char) (n + '0');
		System.out.printf(" %2d -> '%c'%n",n,cc);
		
		//6. change char digit to int digit : subtract the value of '0'
		cc = '7';
		n = cc - '0';
		System.out.printf(" '%c'-> %2d%n",cc,n);
		
	}
	
/* OUTPUT
 66 -> 'B'
 'E'-> 69
  4 -> 'D'
  4 -> 'd'
 'J'-> 10
  3 -> '3'
 '7'->  7
*/

}