Problem inserting data into a vector

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I have the Door, Building and Main classes:

public class Porta {
boolean aberta;
String cor;
double dimensaoX, dimensaoY, dimensaoZ;

void abre() {
    this.aberta = true;
}
void fecha() {
    this.aberta = false;
}
void pinta(String cor) {
    this.cor = cor;
}
boolean estaAberta() {
    boolean estaAberta = false;
    if(aberta == true) estaAberta = true;
    return estaAberta;
}



public class Edificio {
String cor;
int totalDePortas;
int totalDeAndares;
Porta portas[];
int elementos = 0;

void pinta(String cor) {
    this.cor = cor;
}

int quantasPortasEstaoAbertas() {
    int qtdPortasAbertas=0;
    for(int i=0; i<this.portas.length; i++) {
        if(portas[i].aberta == true) qtdPortasAbertas++;
    }
    return qtdPortasAbertas;
}

void adicionaPorta(Porta porta) {
    for(int i=0; i<this.portas.length; i++) {
        if(this.portas[i] == null) this.portas[i] = porta;
    }
}

int totalDePortas() {
    int totalPortas=0;
    for(int i=0; i<this.portas.length; i++) {
        if(this.portas[i] != null) totalPortas++;
    }
    return totalPortas++;
}

void adicionaAndar() {
    this.totalDeAndares = totalDeAndares+=1;
}

int totalDeAndares() {
    return this.totalDeAndares;
}


public class Exer05 {

public static void main(String[] args) {
    //A
    Porta p1 = new Porta();
    p1.abre();
    p1.fecha();
    p1.pinta("Azul");
    p1.pinta("Verde");
    p1.dimensaoX = 1.80;
    p1.dimensaoY = 1.00;
    p1.dimensaoZ = 1.80;
    if(p1.estaAberta() == true) System.out.println("A porta"
            + " está aberta");
    else System.out.println("A porta está fechada");

    //B
    Edificio ed = new Edificio();

    Porta p2 = new Porta();
    p1.fecha();
    ed.adicionaPorta(p2);
    Porta p3 = new Porta();
    p1.abre();
    ed.adicionaPorta(p3);
    Porta p4 = new Porta();
    p1.abre();
    ed.adicionaPorta(p4);
    Porta p5 = new Porta();
    p1.abre();
    ed.adicionaPorta(p5);
    Porta p6 = new Porta();
    p1.abre();
    ed.adicionaPorta(p6);
    Porta p7 = new Porta();
    p1.fecha();
    ed.adicionaPorta(p7);

    ed.quantasPortasEstaoAbertas();

}

It turns out that when I call the added methodPort() in the main class, the following error happens: 

Exception in thread "main" java.lang.NullPointerException
at br.edu.utfpr.exer05.Edificio.adicionaPorta(Edificio.java:23)
at br.edu.utfpr.exer05.Exer05.main(Exer05.java:24)

How to solve?

Thank you

java array nullpointerexception

  • Hello, I’m also new to programming but you have to, in the method where you put how many doors you have to put +1 in the cycle right in front of where the method of seeing the string length is, sorry if n can explain well but I prefer to speak English :p

  • Already solved, I used the collection Arraylist for this.

2 answers

4


Dude, why don’t you try using java.util’s Arraylist? Easier to insert and process Array data.

import java.util.ArrayList;
import java.util.List;

public class Edificio{
    private List<Porta> portas = new ArrayList<Porta>();
    public void adicionaPorta(Porta porta){
        this.portas.add(porta);
    }
}

This way you create a Port-type Arraylist, and with the method add you add a new item to it. Then if you need to, you can fetch the value using the method get.

  • Thank you, I’ll read about!

  • I researched and implemented, it worked too, thank you!

3

  • It worked that way, thank you. I will continue the exercise and if not error, report here, thanks!!

  • Good! , I don’t recommend using this data structure, but for learning purposes it’s worth; .

  • One more thing, in the Building class, the Gate method Bertas() does not return the open doors, you know why?

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