Java help with the concept of how to relate classes

Question

package br.edu.utfpr.exer05;

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;
    }

}

package br.edu.utfpr.exer05;

import java.util.ArrayList;

public class Edificio {
    String cor;
    int totalDePortas;
    int totalDeAndares;
    ArrayList<Porta> portas = new ArrayList<Porta>();

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

    int quantasPortasEstaoAbertas() {
        int qtdPortasAbertas = 0;
        for(int i=0; i<portas.size(); i++) {
            portas.get(i);
            if(portas.get(i).estaAberta() == true) {
                qtdPortasAbertas++;
            }
        }
        return qtdPortasAbertas;
    }

    void adicionaPorta(Porta porta) {
        this.portas.add(porta);
    }

    int totalDePortas() {
        return this.portas.size();
    }

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

    int totalDeAndares() {
        return this.totalDeAndares;
    }
}

package br.edu.utfpr.exer05;

public class Casa {
    String cor;
    Porta porta1, porta2, porta3;

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

    int quantasPortasEstaoAbertas() {
        int qtdPortasAbertas=0;
        if(porta1.estaAberta() == true) qtdPortasAbertas++;
        if(porta2.estaAberta() == true) qtdPortasAbertas++;
        if(porta3.estaAberta() == true) qtdPortasAbertas++;
        return qtdPortasAbertas;
    }

    int totalDePortas() {
        return 3;
    }
}

Answer 1

I would solve this problem there another way.

Door-class:

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

    public void Porta(boolean aberta, String cor, double dimensaoX, double dimensaoY, double dimensaoZ){
        this.aberta = aberta;
        this.cor = cor;
        this.dimensaoX = dimensaoX;
        this.dimensaoY = dimensaoY;
        this.dimensaoZ = dimensaoZ;
    }

    public void Porta(){
        //Atributos padrões apenas para inicialização. Poderiam ser quaisquer outros.
        aberta = false;
        cor = "azul";
        dimensaoX = 2.00;
        dimensaoY = 1.00;
        dimensaoZ = 0.5;
    }

    void abre() {
        this.aberta = true;
    }

    void fecha() {
        this.aberta = false;
    }

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

    boolean estaAberta() {
        return aberta;
    }
}

It is highly recommended that you always have a constructor to initialize the variables. You can have more than one constructor, when you don’t put any, the java compiler puts a blank.

The way it is now, even when you instantiate the Port class with the default constructor, you won’t run the risk of raising Nullpointer, because the default constructor already initializes the variables before you start using them.

boolean estaAberta() {
        boolean estaAberta = false;
        if(aberta == true) estaAberta = true;
        return estaAberta;
    }

This thing you did doesn’t make any sense, and it’s a very common mistake when learning to program. It works, but it’s very ugly. You want a method that tells you whether the door is open or not and you have an 'open' variable that tells you this, now, why not just return it? It is true or false, if it is open it will return true if it is closed it will return False, it is over, you do not need to do all that you did.

if(aberta == true)...

This is also very ugly and extremely unnecessary. The 'open' variable is already a Boolean, it does not need to be compared with false or true, because it already has one of the two values, just do:

if(aberta)...

If opened is true, it will enter if, if it is not, it will not.

Edificio Class:

public class Edificio {
    String cor;
    int totalDeAndares;
    ArrayList<Porta> portas;

    public void Edificio(String cor, int totalDeAndares, ArrayList<Porta> portas){
        this.cor = cor;
        this.totalDeAndares = totalDeAndares;
        this.portas = portas;
    }

    public void Edificio(){
        //Valores padrao.
        portas = new ArrayList<>();
        cor = "azul";
        totalDeAndares = 1;
    }

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

    int quantasPortasEstaoAbertas() {
        int qtdPortasAbertas = 0;
        for(int i=0; i<portas.size(); i++) {
            if(portas.get(i).estaAberta()) {
                qtdPortasAbertas++;
            }
        }
        return qtdPortasAbertas;
    }

    void adicionaPorta(Porta porta) {
        this.portas.add(porta);
    }

    int totalDePortas() {
        return this.portas.size();
    }

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

    int totalDeAndares() {
        return this.totalDeAndares;
    }
}

The total attribute does not make any sense, since you can get it with the size of Arraylist. Unless it means the maximum number of doors, but since you didn’t say anything, I don’t think.

if(portas.get(i).estaAberta() == true)...

That I’ve commented on before.

Casa Class:

This is the wrong part of your code. The most important things in Object Orientation is Polymorphism and Heritage.

House is a kind of Building, so I can say that the Building class is the mother of House.

My House class is all there. Look at you:

public class Casa extends Edificio {

    public void Casa(){
        super.Edificio();
    }
}

Now go to Main there and do it:

Edificio casa = new Casa();

casa.pinta("Laranja");

System.out.println(casa.cor);

The result will be: Laranja

Magic? No, it’s Polymorphism + Heritage.

Do you know why this happened? Because as a house is a kind of building, I extended the Class to Building. ALL, I SAID ALL, the attributes and methods of the Building class are now also House Class without you having to write in Home.

I recommend that you play there with the classes and see the size of the power of polymorphism and heritage.

Any questions just ask.