Generating new objects using existing objects

Question

I’m having a hard time doing this.

Supposing I have two objects of the kind Person, which has the attributes name and employment.

P1 (name=John, job=Taxi driver)

P2 (name=Maria, job=Programmer)

Then I would like to generate the possible combinations of these two objects, of course without attributes errors, for example an object having for example the name Taxi driver.

The way out I would need in case.

P3 (name=John, job=Programmer)

P4 (name=Maria, job=Taxi driver)

How can I do that? There are libraries that allow me?

EDIT

An example of code would look something like this:

...

Pessoa p1 = new Pessoa("João","Taxista");
Pessoa p2 = new Pessoa("Maria", Programador;

List<Pessoa> listaDePessoas = new ArrayList<Pessoa>;
listaDePessoas.add(p1);
listaDePessoas.add(p2);

List<Pessoa> novaLista = new ArrayList<Pessoa>;

novaLista = geraCombinacoes(listaDePessoas); //esse seria o método por exemplo.

Ai when printing that list the output would be:

(João, Taxista)

(Maria, Programador)

(João, Programador)

(Maria, Taxista)

Answer 1

The algorithm below works for three attributes. For an arbitrary amount a more elegant solution is to use Reflection in order to discover these attributes on-the-fly. If the attributes are always the 6 cited in the comment and the number of objects is small, complete with 3 more is nested and solve the problem, whatever it is.

class Pessoa {

    public Pessoa(String nome, String emprego, String endereco) {
        this.nome = nome;
        this.emprego = emprego;
        this.endereco = endereco;
    }

    String nome;
    String emprego;
    String endereco;

    public String toString() {
        return nome +  " - " + emprego + " - " + endereco;
    }
}


public static void main(String[] args) {
    List<Pessoa> pessoas = new ArrayList<Pessoa>();

    pessoas.add(new Pessoa("Joao","Programador","ACD"));
    pessoas.add(new Pessoa("Jose","Analista","DFSD"));
    pessoas.add(new Pessoa("Maria","Gerente","ASEW"));
    pessoas.add(new Pessoa("Pedro","Tester","VCVC"));

    List<Pessoa> resultado = new ArrayList<Pessoa>();

    for(int i = 0; i < pessoas.size(); i++)
        for(int j = 0; j < pessoas.size(); j++)
            for(int k = 0; k < pessoas.size(); k++)
                resultado.add(new Pessoa(pessoas.get(i).nome, pessoas.get(j).emprego, pessoas.get(k).endereco));                              

    for(int i = 0; i < resultado.size(); i++) {
        System.out.println(resultado.get(i));
    }
}

Updating

I think it is important to mention the complexity of the above algorithm. For three attributes complexity is O(n * n * n) or O(n³). Each acidified attribute will add one more loop and thus add + 1 to the exponent. Thus, with 6 attributes the complexity is O(n⁶).

Generalizing, the complexity is O(n^m), where n is the number of people and m the number of attributes.

Anyway, this is a classic example of an algorithm that doesn’t scale well. Depending on the size of n and m it can become impossible to run it. Anyway, there is not much to do, since it is necessary to generate all combinations.

to learn more about complexity see this beautiful answer: /a/56868/3084