Remplazar letras de una cadena

[farfar]

Hola que tal, pues aqui esta para el complementario

Código:

public static void main(String[] args) throws FileNotFoundException, IOException {
        // TODO code application logic here

        BufferedReader textfil=new BufferedReader(new FileReader("S1.txt"));

		try {
			String line;
			while(textfil.ready()){
	                        line = textfil.readLine();

	        String ch=line;
	        StringBuffer chBuf=new StringBuffer(ch); System.out.println("Sequence  "+chBuf);

	        chBuf.reverse();	System.out.println("Sequence inverse  "+chBuf);


                System.out.println("Complementaria:");


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

                    
                    char caract = chBuf.charAt(i);
                    char acum = Main.Convert(caract);
                    

                    System.out.println(acum);
                    

                }

			}
		}
                
                catch(IOException ex){}


		finally {
			textfil.close();
		}

    }

    public static char Convert(char c){

        if(c == 'T'){

            result = 'A';
        }
        else if(c == 'A'){

            result = 'T';
        }
        else if(c == 'G'){

            result = 'C';
        }
        else if(c == 'C'){

            result = 'G';
        }
        return result;
    }

}

Espero te sea de utilidad

saludos