[RESOLVIDO]Como repetir se nao for a letra que eu desejo

import java.io.PrintStream;
import java.util.Scanner;

public class Programa {

    public static void main(String[] args) {
        try {
            Programa programa = new Programa();
            programa.executar();
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

    private static final Scanner entrada = new Scanner(System.in);
    private static final PrintStream saida = System.out;

    public void executar() throws Exception {
        String sexo = lerSexo();
        saida.println("Sexo informado: " + sexo);
    }

    private String lerSexo() {
        while (true) {
            saida.println("Seu Sexo [M/F]:");
            String sexo = entrada.nextLine();
            switch (sexo.charAt(0)) {
                case 'M':
                case 'F':
                    return sexo;
            }
            saida.println();
            String CSI = "\u001B[";
            saida.println("------------------");
            saida.print(CSI + "31" + "m");
            saida.print("Sexo Inválido");
            saida.println(CSI + "m");
            saida.println("-------------------");
        }
    }
}