How do I complete my Caesar Cipher?

import java.util.Scanner;

public class Encryption {
	public Encryption () {
		//Empty constructor.
	}
	
	public void run() {
		
		boolean quit = false;
		Scanner input = new Scanner(System.in);
		
		while(quit == false)
		{
			
			System.out.println("Please enter a number between 1 and 26 or q to quit.\n");
			
			// Accept the user input
			String userKey = input.next();
			
			// Check to see if the user is quitting instead of entering in a new number
			if( userKey.charAt(0) == 'q' )
			{
				quit = true; 
				// Exits out of the loop
				System.out.println("Now exiting...");
			}
			
			else
			{
				// Convert user input into a number
				int userNum = Integer.parseInt(userKey);
				
				// Check if the number is within the valid range
				if( userNum > 0 || userNum < 27 )
				{
					System.out.println("Enter the message you wish to encrypt:\n");
					String userMessage = input.next();
					
					for(int i = 0; i < userMessage.length(); i++)
					{
						userMessage.charAt(i);
					}
					
				}
				
				else
				{
					System.out.println("Error: Please enter a number between 1 and 26 or q to quit.");
				}
				
			}
		}
		
		// Close the input stream
		input.close();
	}
}