Doubt with POO exercise in Java - problem with array

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Doubt with POO exercise in Java - problem with array

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#1 by (2 votes)
#2 by (1 votes)

1

I have a question with an exercise that says: Create a Book class with loan, return and toString methods.

I want the vector to grow as the number of books grows, but in codigo.length , codigo appears as not being initialized. What am I doing wrong? Can someone help? Thanks!

private String titulo;
private String autor;
private String genero;
private static int codigo;
private static int stock=0;

 public Libro(String titulo, String autor, String genero, int codigo, int stock){

     this.titulo=titulo;
     generaCodigo();
     this.autor=autor;
     this.genero=genero;
 }

 public Libro(String titulo){

//El genera codigo me da error, me dice que cree un objeto

    this("titulo", "desconocido", "a confirmar", generaCodigo(), 0);

 }

public static void generaCodigo (){

//Acá me sale un error como que la variable codigo, en codigo.length no fue inicializada         

    int [] codigo = new int [codigo.length];

      for(int i=0; i>=codigo.length; i++){

         codigo[i]=i;
      }

      stock+=1
}

java array poo

asked by Brenda Yanela Conzi 03.03.2018 в 23:39

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2 answers

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score 2 · Answer 1

This line:

int [] codigo = new int [codigo.length];

It does not make sense because you're trying to create an array of unknown length. If you break that line in two, you will notice the error:

int [] codigo; //código está declarado pero no inicializado
codigo = new int [codigo.length];

You are asking that codigo be an array and that its length be equal to its current length. Since currently codigo does not exist, it does not have length.

score 1 · Answer 2

This line is wrong:

int [] codigo = new int [codigo.length];

You are giving it an unknown length, because the codigo attribute of your book class is never initialized. Another thing, do not use the same name of a class attribute for a local variable, because you do something called hide field and it's bad programming practice.