Implement a method that accepts (List <String []> rows, int columnIndex) and sorts arrays of rows (table entries) by column

There is an interface in which the method is declared.

void sort(List<String[]> rows, int columnIndex); 

You need to implement this interface in its class.

 public class Task1Impl implements IStringRowsListSorter, Comparator<String[]>{ //реализация должна работать, как singleton. даже при использовании из нескольких потоков. public static final IStringRowsListSorter INSTANCE = new Task1Impl(); @Override public void sort(final List<String[]> rows, final int columnIndex) { //моя реализация } 

The method takes as parameters:

rows - table. (List is, as I understand it, a list of arrays of type String! I understand, the table itself, for example, the result of the query)

columnIndex - the field number in this table (column index) by which you want to sort. In our structure it is String, it turns out.

I understand that sorting needs to be done using the Comparator. that is, the class must be redefined:

  @Override public int compare(String[] o1, String[] o2) {} 

We basically have to sort the records in the tables, which we pass to the Comparator, but how can we explain to it what we need, sort by rows, because in the Comparator we cannot also pass columnIndex -

  @Override public int compare(String[] o1, String[] o2, int columnIndex) { o1[columnIndex] < o2 [columnIndex] } 

To work with this interface, I created a test class, so I’m asking you to see if you made the structure correctly for working with the array and its output through for each

 public class TestIStringRowsListSorter { List<String[]> rows = new ArrayList<String[]>(); public List<String[]> getStruct(){ return rows; } public void init(){ String[] query1 = new String[3]; // массив строк - строка таблицы query1[0] = "Contact"; // 1а строка - 1а запись (1о поле) query1[1] = "1"; // 1а строка - 1а запись (1о поле) query1[2] = "Peter"; // 1а строка - 1а запись (1о поле) String[] query2 = new String[3]; query2[0] = "Contact"; query2[1] = "2"; query2[2] = "Helga"; rows.add(query1); // добавляем в тестовый Список из массивов строк 1 массив строк rows.add(query2); // добавляем в тестовый Список из массивов строк 1 массив строк } public void showInitStruct(){ //разобраться как реализован НОВЫй с джава 1.5 способ перебора for (String[] tmp: rows){ //для каждого массива строк в списке System.out.println("String[] array number " + rows.indexOf(tmp)); for (String column : tmp) // для каждой строки в массиве строк { System.out.println(column); } } } public String goTest() { return "Sucefull"; } } 

Logic class:

 TestIStringRowsListSorter t = new TestIStringRowsListSorter(); t.init(); t.showInitStruct(); 

Logic execution result:

 String[] array number 0 Contact 1 Peter String[] array number 1 Contact 2 Helga 

The last 2 classes created to simplify the work. The question, in fact, is how to do the sorting using Java tools — implement the Comparator, and sort through the standard collection methods, and if so, how to do it?