Doubt about constructor and show.Input dialog

Question

Hi everybody!
I wrote this program in java. It works, but I have some doubts. The points that are not clear to me are in comments. Thanks in advance:
import javax.swing.JOptionPane;
public class Bicicleta extends JOptionPane{
     int velocidad;
     int cambios;
     String color;
public Bicicleta(){// Why we have to make a constructor without procedures, if we have the constructor public Bicicleta(values) down?
                         //I mean, if we delete this constructor,
                         // the program will not work.
public Bicicleta(int cambiarVelocidad, int cambiarCambios, String cambiarColor){ //without the constructor bicicleta
     velocidad = cambiarVelocidad;                                                            // that is up of this procedure,     
     cambios = cambiarCambios;                                                                 // the program will not work, Why?
     color = cambiarColor;
public int getVelocidad(){
     return velocidad;
public int getCambios(){
     return cambios;
public String getColor(){
     return color;
public void setVelocidad(int nuevaVelocidad){
     velocidad = nuevaVelocidad;
public void setCambios(int nuevoCambio){
     cambios = nuevoCambio;
public void setColor(String nuevoColor){
     color = nuevoColor;
public void showBici(){
     this.showMessageDialog(null, "Los valores de la nueva bicicleta son: Velocidad de "+velocidad+" tiene "
     cambios" cambios y es de color "+color);
public Bicicleta getBici(){
     return (new Bicicleta(this.getVelocidad(),this.getCambios(),this.getColor()));
public void setBicicleta(){
     velocidad = Integer.parseInt(this.showInputDialog("Inserte la velocidad de la bicicleta"));
     cambios = Integer.parseInt(this.showInputDialog("Inserte la cantidad de cambios de la bicicleta"));
     color = (this.showInputDialog ("Inserte el color de la bicicleta"));
public static void main(String[] args){
     Bicicleta bike = new Bicicleta();
     bike.setBicicleta();
     Bicicleta nuevaBici; // I copy this segment of code form anyone else, but I dont understand it.
     nuevaBici = bike.getBici();          // Can someone explain it please?
     nuevaBici.showBici(); //
}

Answer 1

The program is supposed to recollect the data with:
public void setBicicleta(){
velocidad =
= Integer.parseInt(this.showInputDialog("Inserte la
velocidad de la bicicleta"));
cambios =
= Integer.parseInt(this.showInputDialog("Inserte la
cantidad de cambios de la bicicleta"));
color = (this.showInputDialog ("Inserte el color de
e la bicicleta"));
So, I think that the values of variables are defined
by the user. So, we dont have to define any previous
data, because it is a input of the program user.
Maybe I?m wrong, so what is my error in this case?Not thinking about responsibilities? So when I go and create a new Bicycle, I have a bicycle with no color and no top speed. Have you ewver seen a bicycle like that? A bycicle that asks you about what color it should have? Shouldn't rather the one creating the bicycle be the one to ask you for the values, and then apply them to the bicycle he creates?
Do the asking first, then call
bike = new Bicicleta(theColor, theSpeed, theGears, whatever);That way you can also get rid of that c'tor you don't want, since it makes no sense anyway.