ERRORnon-static variable this can not be referenced from a static context

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ERRORnon-static variable this can not be referenced from a static context

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#1 by (0 votes)

1

I am implementing a class that allows me to create a linked list. But at the moment of instantiating a new linked list, I miss this error:

MainListaEnlazada.java:19: error: non-static variable this can not be referenced from a static context LinkedList list = new LinkedList ();

Could someone explain to me what I did wrong?

    public class MainListaEnlazada {
    public static void main(String[] args){
        ListaEnlazada lista = new ListaEnlazada();

    }

    class Nodo {
        private Object valor;
        private Nodo siguiente;

        public Nodo(Object valor){
            this.valor = valor;
            this.siguiente = null;
        }

        public void enlazarSiguiente(Nodo n) {
            this.siguiente = n;
        }

        public Object getValor(){
            return valor;
        }

        public Nodo getSiguiente() {
            return siguiente;
        }

    }

    class ListaEnlazada {
        private Nodo cabeza;
        private int size;

        ListaEnlazada(){
            cabeza = null;
            size = 0;
        }

        public void prepend(Object _element) {
            if(cabeza == null){
                cabeza = new Nodo(_element);
            } else {
                Nodo temp = cabeza;
                Nodo nuevo = new Nodo(_element);
                nuevo.enlazarSiguiente(temp);
                cabeza = nuevo;
            }

            this.size++;
        }

        public boolean vacia(){
            return (cabeza == null)?true:false;
        }

        public int size(){
            return this.size;
        }
    }
}

java

asked by Jax95 29.10.2017 в 21:43

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1 answer

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score 0 · Accepted Answer

That's why you're using internal classes, what you have to do is write the internal classes in the following way:

public static class Nombre_Clase_Interna {

....

}

In your case it would look like this:

public class MainListaEnlazada {
public static void main(String[] args){
    ListaEnlazada lista = new ListaEnlazada();

}

static class Nodo {
    private Object valor;
    private Nodo siguiente;

    public Nodo(Object valor){
        this.valor = valor;
        this.siguiente = null;
    }

    public void enlazarSiguiente(Nodo n) {
        this.siguiente = n;
    }

    public Object getValor(){
        return valor;
    }

    public Nodo getSiguiente() {
        return siguiente;
    }

}

static class ListaEnlazada {
    private Nodo cabeza;
    private int size;

    ListaEnlazada(){
        cabeza = null;
        size = 0;
    }

    public void prepend(Object _element) {
        if(cabeza == null){
            cabeza = new Nodo(_element);
        } else {
            Nodo temp = cabeza;
            Nodo nuevo = new Nodo(_element);
            nuevo.enlazarSiguiente(temp);
            cabeza = nuevo;
        }

        this.size++;
    }

    public boolean vacia(){
        return (cabeza == null)?true:false;
    }

    public int size(){
        return this.size;
    }
    }
}

Another alternative to solve your problem is to place each class within its own file, in this case it would no longer be necessary to put static classes.