On Mar 31, 1:36 am, jose luis garcia <[email protected]> wrote:
> *Hello everybody... I have a problem. I wrote a code for a program that have
> 1 superclass and 1 class extends. the code it`s follow:*
>
> //Programa que realiza algunos calculos mediante las caracteristicas de un
> cilindro
>
> package cilindro;
>
> // @author louis
>
> import java.util.Scanner;
>
> public class Cilindro {
> double pi = Math.PI;
>
> public Cilindro(){
> // super();
>
> }
>
> public double areaCilindro(double r, double h){
> double area = (2*pi*r*h) + (2*pi*r*r);
>
> return area;
> }
>
> public double perimetroCilindro(double r, double h){
> double perimetro = (4*pi*r)+(2*h);
>
> return perimetro;
>
> }
>
> public class Circulo extends Cilindro{
>
> Circulo(){
> super();
> }
>
> public double areaCirculo(double r){
>
> double area = pi*r*r;
> return area;
> }
>
> public double perimetroCirculo(double r){
> double perimetro = 2*pi*r;
>
> return r;
> }
>
> }
>
> public static void main(String[] args) {
>
> // Cilindro obj = null;
> Circulo obj1 = null;
I suspect the culprit is the inner class. If I remember correctly, an
inner class type declaration should be like:
Cilindro.Circulo obj1 = null;
> double radio = 0,altura = 0;
> Scanner input = new Scanner(System.in);
>
> System.out.println("Ingresa Radio: ");
> radio = input.nextFloat();
>
> /* System.out.println("Ingresa altura: ");
> altura = input.nextFloat();
> */
> String resultado = "Area del circulo: " +
> obj1.areaCirculo(radio);
>
> System.out.println(resultado);
>
> }
>
> }
>
> *Netbeans not generate any error. But at the moment that run the program and
> insert a float, Netbeans generate me this message:*
>
> run:
> Ingresa Radio:
> Exception in thread "main" java.lang.NullPointerException
> at cilindro.Cilindro.main(Cilindro.java:66)
> 2.23
> Java Result: 1
> GENERACIÓN CORRECTA (tiempo total: 3 segundos)
>
> *
> I`m sure that is a logic error... help me please. Thanks!
> *
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