public class Osoba implements Comparable<Osoba>
{
    private String name;
    private String surname;
    private String nip;
    private kraj country;

    public Osoba(String name, String surname, String nip, kraj country)
    {
        this.name = name;
        this.surname = surname;
        this.nip = nip;
        this.country = country;
    }

    @Override
    public int compareTo(Osoba o)
    {
        String tocompare = o.getsurname();
        if (this.surname.equalsIgnoreCase(tocompare))
        {
            return 0;
        }
        else
        {
            if (this.surname.compareTo(tocompare) == -1)
            {
                return -1;
            } else
            {
                return 1;
            }
        }
    }

    @Override
    public String toString()
    {
       return this.nip +  " " +this.surname+ " " + this.name;
    }

    public String getsurname()
    {
        return surname;
    }

}

6438088470 Mcpherson Jemima
4728926902 Mcpherson Neville
8093413641 Ballard Neville
8485620409 Mcpherson Neville
6118892423 Ballard Fallon
3110453986 Ballard Sybill
3338278297 Mcpherson Sybill
2797735926 Mcpherson Todd
7473716746 Mcpherson Evelyn
9519145537 Mcpherson Ima
After sorting:
6438088470 Mcpherson Jemima
4728926902 Mcpherson Neville
8093413641 Ballard Neville
8485620409 Mcpherson Neville
6118892423 Ballard Fallon
3110453986 Ballard Sybill
3338278297 Mcpherson Sybill
2797735926 Mcpherson Todd
7473716746 Mcpherson Evelyn
9519145537 Mcpherson Ima

if (this.surname.compareTo(tocompare) == -1)

if (this.surname.compareTo(tocompare) < 0)

@Override
public int compareTo(Osoba o)
{
    return this.surname.compareToIgnoreCase(tocompare.getsurname()));
}

@Override
public int compareTo(Osoba o)
{
    if (!this.surname.equalsIgnoreCase(o.getSurname()))
    {
        return this.surname.compareToIngoreCase(o.getSurname());
    }
    else
    {
        return this.name.compareToIngoreCase(o.getName());
    }
}