Q:

Clear a list after adding its elements to another list

I'm doing a program that gets as parameter more sentences. And I made 2 lists, one called "propozitie", which contains each sentence, and one called "propozitii", which contains all sentences.
The problem is: When I clear the "propozitie" list after it meets a ".", it also clears the "propozitii" list and it's ending up by printing 3 empty lists.
Input data: 

Andrei goes there. Andrei plays football. I enjoy staying home.

Can anybody help me ? 
Thanks in advance.
import java.util.ArrayList;
import java.util.List;

public class Propozitie {

private static List<List<String>> propozitii;
private static List<String> propozitie;

public static void main(String args[]) {

    propozitii = new ArrayList<List<String>>();
    propozitie = new ArrayList<String>();

    for (String arg : args) {
        propozitie.add(arg);

        if (arg.contains(".")) {
            propozitii.add(propozitie);
            propozitie.clear();
        }

    }

    System.out.println(propozitii);

}
}

A:

This is because, the statement 
propozitii.add(propozitie);
adds the reference to propozitie to propozitii list. A copy of the object is not added. To do a copy, use this.
propozitii.add(new ArrayList<String>(propozitie));
now you can clear propozitie

