Question in caesar encryption code

package encryption;
import java.util.*;
/**
 *
 * @author Toshiba
 */
public class Encryption {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
      //  ENCR n =new ENCR();
       Scanner S = new Scanner(System.in);
       System.out.print(" Enter the text");    
        String massege  = S.next();
       System.out.print(" Enter the kay");    
        int key = S.nextInt();
    }
  
    public String NN (  String massege  , int kay )
    
    {
    
    String  STR= "ABCDEFGHIJKLMNOPQRSTWXYZ" ; 
    char current;
    String chyfer= ""; 
    for (int i=0; i<=massege .length();i++)
    {
    
    current = massege .charAt(i);
    
    for (int y= 0 ; y<=STR.length(); y++) {
            if(current==STR.charAt(y))
            {
             
             chyfer + = STR.charAt((kay+y)%26);
             
             return chyfer ;
             
             }
        }
    }
     return chyfer ;
    }
}