How to sort 2D ArrayList <String> only by the first element

Question

To avoid duplicate statements , I looked through this article and this is not quite what I wanted.
Every other two-dimensional ArrayList question involved numbers doubleor int; my question is about Strings.

What am I doing

I have a 2D ArrayList defined as follows:

ArrayList<ArrayList<String>> namesAndNumbers = new ArrayList<ArrayList<String>>();

The idea is that the first element in each row of ArrayLists contains the names, and the remaining columns in each row contain phone numbers (unknown amount). Therefore, I would like to avoid converting it to a regular array.

Example

Say I populated my ArrayList and I have this:

{"Mike", "[phone]"}
{"Emily", "[phone]", "[phone]"}
{"James", "[phone]"}

I expect my output to be as follows:

{"Emily", "[phone]", "[phone]"}    
{"James", "[phone]"}
{"Mike", "[phone]"}

, , .

, , - 2D ArrayList . , . .

Answer 1

Collections.sort Comparator, , :

List<ArrayList<String>> namesAndNumbers = new ArrayList<ArrayList<String>>();
namesAndNumbers.add(new ArrayList<String>(Arrays.asList("Mike", "[phone]")));
namesAndNumbers.add(new ArrayList<String>(Arrays.asList("Emily", "[phone]", "[phone]")));
namesAndNumbers.add(new ArrayList<String>(Arrays.asList("James", "[phone]")));
Collections.sort(namesAndNumbers, new Comparator<ArrayList<String>>() {    
        @Override
        public int compare(ArrayList<String> o1, ArrayList<String> o2) {
            return o1.get(0).compareTo(o2.get(0));
        }               
});
System.out.println(namesAndNumbers);

:

[[Emily, [phone], [phone]], [James, [phone]], [Mike, [phone]]]

Answer 2

:

final Comparator<List<String>> comparator = new Comparator<List<String>>() {
    public int compare(List<String> pList1, List<String> pList2) {
        return pList1.get(0).compareTo(pList2.get(0));
    }
};
final List<List<String>> lists = Arrays.asList(
    Arrays.asList("Mike", "[phone]"),
    Arrays.asList("Emily", "[phone]", "[phone]"),
    Arrays.asList("James", "[phone]")
);
Collections.sort(lists, comparator);
for (List<String> list : lists) System.out.println(list);

Answer 3

For a change. Why don't you use HashMap if you don't want to duplicate keys. the key will be a name and the value will be an ArrayList of numbers

String name="John";

ArrayList<String> phonenumbers=new ArrayList<String>();

phonenumbers.add("80925887");
phonenumbers.add("[phone]");

TreeMap<String, ArrayList> tm=new TreeMap<String, ArrayList>();

tm.put(name, phonenumbers);