Non-static variable can not be referenced from non-static context

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Non-static variable can not be referenced from non-static context

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#1 by (3 votes)

4

I'm using a context where I have a variable of type array with reference to another class. When trying to declare the object-instantiated class and declare its size this error is returned and I would like to understand why:

non-static variable can not be referenced from a static context

The error line is e1.empregados = new Funcionario[TAM]; in:

public class EmpresaTest
{
public static int posicao = 0;
public static boolean t = true;
public final int TAM = 5;



public static void main(String[] args)
{


    Funcionario f1 = new Funcionario();
    Funcionario f2 = new Funcionario();
    Funcionario f3 = new Funcionario();
    Funcionario f4 = new Funcionario();

    Empresa e1 = new Empresa();

    e1.empregados = new Funcionario[TAM];

    t = Booelan.parseBoolean(e1.adicionaEmpregado(f1));
    System.out.println("T: " + t);

    e1.adicionaEmpregado(f2);
    e1.adicionaEmpregado(f3);

    e1.contemFuncionario(f1);
    e1.contemFuncionario(f2);
    e1.contemFuncionario(f3);
    e1.contemFuncionario(f4);


    /*e1.empregados[0] = f1;
    e1.empregados[1] = f2;
    e1.empregados[2] = f3;*/
    }
    }

public class Empresa
{    
public  int idEmpresa;
public  int razaoSocial;
public  String cnpj;
public  Funcionario empregados[];

public int getIdEmpresa() {
    return idEmpresa;
}

public void setIdEmpresa(int idEmpresa) {
    this.idEmpresa = idEmpresa;
}

public int getRazaoSocial() {
    return razaoSocial;
}

public void setRazaoSocial(int razaoSocial) {
    this.razaoSocial = razaoSocial;
}

public String getCnpj() {
    return cnpj;
}

public void setCnpj(String cnpj) {
    this.cnpj = cnpj;
}

public Funcionario[] getEmpregados() {
    return empregados;
}

public void setEmpregados(Funcionario[] empregados) {
    this.empregados = empregados;
}

public void adicionaEmpregado(Funcionario f)
{
    int i = 0;

    if(this.empregados[i] != null)
    {
        this.empregados[i] = f;
        i++;
    }
    else
    {
        System.out.println("Não dá para adicionar mais funcionários");
    }

    /*for(int i = 0; i < empregados.length; i++)
    {
        this.empregados[i] = f;
    } */

}

public void mostrarEmpregados()
{
    for(int i = 0; i < empregados.length; i++)
    {
        System.out.println("Valor: " + i + " é o empregado: " + this.empregados[i]);
    }
}

boolean contemFuncionario(Funcionario f)
{
    boolean func = false;
    for(int i = 0; i < empregados.length; i++)
    {
        if(this.empregados[i] == f)
        {
            System.out.println("Empregado existente!");
            func = true;
        }
        else
        {
            System.out.println("Não encontrado!");
            func = false;
        }
    }
    return func;
}

java array

asked by anonymous 09.09.2014 / 03:19

1 answer

How to work with associative table with additional attributes in REST? Java interface layout

score 3 · Answer 1

The problem in this case is that you are trying to access an instance variable in a static context.

Instance variables belong to the scope of a given object, an instance of a class.

If for example you do:

public class Foca {
    public int qtdFilhos;
}

It means that each instance of class Foca (an object) will have its own value for the variable qtdFilhos .

In this code:

public class Foca {
    public int qtdFilhos;

    public static void listarFamilia() {
        Foca[] familia = new Foca[qtdFilhos + 2];
    }
}

Accessing the variable qtdFilhos in this method does not make sense, because which of the objects in the Foca class are you referring to? It is the same situation with class EmpresaTest . When you access the TAM attribute, which of the instances you refer to (we know that there may only be one or a specific variable, but the compiler does not)?

To correct the problem you need, like the other attributes above it, to add the static modifier, making it a class variable .

Class variables are unique to all instances of a class over the same ClassLoader .

This means that at any time during the execution of your program, from the first access, that is where ClassLoader initializes it, except in case the variable is final (the JVM does an optimization where value is initialized along with bytecode), any access to it will be shared by all.

To fix the problem, change your code to:

public class EmpresaTest {
    public static int posicao = 0;
    public static boolean t = true;
    public static final int TAM = 5; // Agora TAM é uma variável de classe

    // Restante do código
}