Frase - apagando caracteres

Agora podemos apagar caracteres contidos
numa frase híbrida com muita facilidade.
A frase é inserida pela entrada de dados
contendo caracteres e dígitos misturados,
Só que desta vez vamos apagar só os caracteres,
os dígitos serão imprimidos normalmente acompanhe:

veja abaixo o código do programa:

import java.util.Scanner;

public class PROJETO {

     public static int tam = 20;

     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 ( " " );

         char [ ] Vet = new char [ tam ];

         int h = 0, k, i = 0, j, lenv, len_v, t;

         char [ ] letras = {

                'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'l', 'm', 'n',

                'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'x', 'z', 'k', 'w', 'y',

                'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'L', 'M', 'N',

                'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'X', 'Z', 'K', 'W', 'Y'};

         String conv = "";

         char [ ] frase = new char [ tam ];

         jht.textcolor ( jht.LIGHTRED );

         jht.gotoxy ( ( int ) 28, ( int ) 3 );

         System.out.printf ( "FRASE - APAGANDO CARACTERES" );

         jht.textcolor ( jht.LIGHTBLUE );

         jht.gotoxy ( ( int ) 16, ( int ) 5 );

         System.out.printf ( "Digite uma frase ==> " );

         jht.textcolor ( jht.LIGHTRED );

         Scanner dados = new Scanner ( System.in );

         conv = dados.nextLine ( );

         frase = conv.toCharArray();

         jht.textcolor ( jht.LIGHTBLUE );

         jht.gotoxy ( ( int ) 16, ( int ) 7 );

         System.out.printf ( "Frase digitada ==> " );

         jht.textcolor ( jht.LIGHTRED );

         for ( i = 0; i < frase.length; i++ ) {

              System.out.print ( frase [ i ] );

         }

         jht.getche ( );

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

         lenv = ( letras.length );

         jht.textcolor ( jht.LIGHTBLUE );

         jht.gotoxy ( ( int ) 16, ( int ) 9 );

         System.out.printf ( "Imprimindo abaixo só os dígitos da frase" );

         jht.textcolor ( jht.LIGHTRED );

         jht.gotoxy ( ( int ) 16, ( int ) 11 );

         for ( i = 0; i < frase.length; i++ ) {

              for ( j = 0; j < lenv; j++ )

                   if ( frase [ i ] == letras [ j ] )

                        break;

              if ( j == lenv ){

                   System.out.print ( frase [ i ] );

                   System.out.print ( " " );

              }

         }

         jht.textcolor ( jht.LIGHTBLUE );

         jht.gotoxy ( ( int ) 20, ( int ) 17 );

         jht.Sleep ( ( short ) 1800 );

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

         jht.textcolor ( jht.LIGHTMAGENTA );

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

         jht.textcolor ( jht.BLACK );

         jht.gotoxy ( ( int ) 20, ( int ) 18 );

         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 ( );

     }

}