Contando caracteres em string

A string é imprimida normalmente,
logo após, é convertida para array de char.
O programa pede para que se digite um
número entre 0 e o tamanho máximo da string,
Se digitar um número maior, recebe uma mensagem
de advertência, se o número digitado estiver
dentro do tamanho da string, o caractere
correspondente a posição será retornado.

Veja abaixo imagens do programa em execução:

Veja abaixo o código do rograma:

import java.util.Scanner;

public class PROJETO {

     public static void main ( String [ ] args ) {

         J jht = new J ( );

         jht.textbackground ( jht.WHITE );

         jht.Moldura ( ( short ) 1, ( short ) 24, ( short ) 2, ( short ) 78 );

         jht.title ( " " );

         int i, j, lenv;

         String conv = "Oliveira";

         lenv = conv.length ( );

         char [ ] str = new char [ lenv ];

         str = conv.toCharArray ( );// convert string para char

         while ( true ) {

              jht.cls ( );

              jht.textcolor ( jht.LIGHTRED );

              jht.gotoxy ( ( short ) 21, ( short ) 3 );

              System.out.printf ( "CONTANDO CARACTERES - SAIR [ -1 ] " );

              jht.textcolor ( jht.LIGHTBLUE );

              jht.gotoxy ( ( short ) 21, ( short ) 5 );

              System.out.printf ( "Nome da string ==> " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "%s", conv );

              jht.textcolor ( jht.LIGHTBLUE );

              jht.gotoxy ( ( short ) 21, ( short ) 7 );

              System.out.printf ( "Total de caracteres ==> " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "%d", lenv );

              jht.textcolor ( jht.LIGHTBLUE );

              System.out.printf ( " letras " );

              jht.textcolor ( jht.LIGHTBLUE );

              // ///////////////////////////////////////////////////

              jht.textcolor ( jht.LIGHTBLUE );

              jht.gotoxy ( ( short ) 21, ( short ) 9 );

              System.out.printf ( "Digite um número entre " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "0" );

              jht.textcolor ( jht.LIGHTBLUE );

              System.out.printf ( " e " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "%d ", lenv - 1 );

              jht.textcolor ( jht.BLACK );

              Scanner sc = new Scanner ( System.in );

              j = sc.nextInt ( );

              if ( j >= lenv ) {

                   jht.textcolor ( jht.LIGHTBLUE );

                   jht.gotoxy ( ( short ) 21, ( short ) 11 );

                   System.out.printf ( "Só digite números entre " );

                   jht.textcolor ( jht.LIGHTRED );

                   System.out.printf ( "0" );

                   jht.textcolor ( jht.LIGHTBLUE );

                   System.out.printf ( " e " );

                   jht.textcolor ( jht.LIGHTRED );

                   System.out.printf ( "%d ", lenv - 1 );

                   jht.Sleep ( ( short ) 800 );

                   jht.textcolor ( jht.LIGHTRED );

                   jht.gotoxy ( ( int ) 29, ( int ) 21 );

                   System.out.printf ( "PRESSIONE QUALQUER TECLA" );

                   jht.getche ( );

                   main ( args );

              }

              // ////////////////////////////////////////////////////

              if ( j == -1 ) {

                   jht.textcolor ( jht.LIGHTBLUE );

                   jht.gotoxy ( ( int ) 22, ( int ) 19 );

                   jht.Sleep ( ( short ) 1800 );

                   System.out.printf ( "Por: " );

                   jht.textcolor ( jht.LIGHTMAGENTA );

                   System.out.printf ( "Samuel Lima" );

                   jht.textcolor ( jht.BLACK );

                   jht.gotoxy ( ( int ) 22, ( int ) 20 );

                   System.out.printf ( "sa_sp10@hotmail.com" );

                   jht.Sleep ( ( short ) 1800 );

                   jht.textcolor ( jht.LIGHTRED );

                   jht.gotoxy ( ( int ) 34, ( int ) 22 );

                   System.out.printf ( "MUITO OBRIGADO" );

                   jht.getche ( );

                   System.exit ( 0 );

              }

              // ////////////////////////////////////////////////////

              jht.textcolor ( jht.LIGHTBLUE );

              jht.gotoxy ( ( short ) 21, ( short ) 11 );

              System.out.printf ( "Na posição " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "%d", j );

              jht.textcolor ( jht.LIGHTBLUE );

              System.out.printf ( " está o caracter " );

              jht.textcolor ( jht.LIGHTRED );

              System.out.printf ( "%c", str [ j ] );

              jht.textcolor ( jht.BLACK );

              jht.Sleep ( ( short ) 800 );

              jht.textcolor ( jht.LIGHTRED );

              jht.gotoxy ( ( int ) 29, ( int ) 21 );

              System.out.printf ( "PRESSIONE QUALQUER TECLA" );

              jht.getche ( );

              // ///////////////////////////////////////////////////

         }

     }

}