Initialize class fields in constructor or at declaration?

Question

I\'ve been programming in C# and Java recently and I am curious where the best place is to initialize my class fields.

Should I do it at declaration?:

Answer 1

There are many and various situations.

I just need an empty list

The situation is clear. I just need to prepare my list and prevent an exception from being thrown when someone adds an item to the list.

public class CsvFile
{
    private List lines = new List();

    public CsvFile()
    {
    }
}

I know the values

I exactly know what values I want to have by default or I need to use some other logic.

public class AdminTeam
{
    private List usernames;

    public AdminTeam()
    {
         usernames = new List() {"usernameA", "usernameB"};
    }
}

or

public class AdminTeam
{
    private List usernames;

    public AdminTeam()
    {
         usernames = GetDefaultUsers(2);
    }
}

Empty list with possible values

Sometimes I expect an empty list by default with a possibility of adding values through another constructor.

public class AdminTeam
{
    private List usernames = new List();

    public AdminTeam()
    {
    }

    public AdminTeam(List admins)
    {
         admins.ForEach(x => usernames.Add(x));
    }
}