Compare Two List

Question

I have a list

List<Comentarios> comentarios
List<Comentarios> comentariosSP

The first list I receive data from a webserver, the second from a Sharedpreferences.

I tried to compare them

comentarios.equals(comentariosSP)

but it always returns false, even though I know the lists are identical.

remembering that I need to check if the attributes data are the same. EX:

comentarios.get(0).getComentario().equals(comentariosSP.get(0).getComentario())

You can do it without going through the whole list?

Answer 1

You can use the method equals() of the List if over-write the method equals() class Comments to indicate when two objects Comets are the same:

@Override
public boolean equals(Object o) {
    // verifica se é o mesmo objecto
    if (this == o)
        return true;
    // verifica se é null
    if (o == null)
        return false;
    // verifica tipo e cast
    if (getClass() != o.getClass())
        return false;

    Comentarios comentarios = (Comentarios) o;
    // Comparação atributo a atributo
    // Note que cada um dos atributos têm também de implementar correctamente o método equals()
    return Objects.equals(atributo1, comentarios.atributo1)
            && Objects.equals(atributo2, comentarios.atributo2) && .....;
}

Note: Two lists are equal if they have the same number of items, equal and in the same order.

Answer 2

When you compare with the comments.equals(commentsSP) method, you are comparing the memory address in which the list is allocated.

using the List equals() you compare the values themselves.