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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. public static void main (String[] args) throws java.lang.Exception
  11. {
  12. ArrayList<Integer> list = new ArrayList<>(Arrays.asList(1,2,3,4,5,6,7,8,1,2,3,4));
  13. int listSize = list.size();
  14.  
  15. ArrayList<ArrayList<Integer>> listArr = new ArrayList<>(listSize/4);
  16.  
  17. for (int i = 0; i < listSize; i += 4) {
  18. ArrayList<Integer> listOfNums = new ArrayList<>();
  19. listOfNums.add(list.get(i + 1));
  20. listOfNums.add(list.get(i + 2));
  21. listOfNums.add(list.get(i + 3));
  22. listOfNums.add(list.get(i));
  23. listArr.add(listOfNums);
  24. }
  25.  
  26. // Это чтоб пробежаться только по уникальным значениям листа.
  27. Set<ArrayList<Integer>> uniqueSet = new HashSet<ArrayList<Integer>>(listArr);
  28.  
  29. for (ArrayList<Integer> temp : uniqueSet) {
  30. System.out.println("counts of " + temp + ": " + Collections.frequency(listArr, temp));
  31. }
  32. }
  33. }
Success #stdin #stdout 0.12s 320576KB
stdin
Standard input is empty
stdout
counts of [2, 3, 4, 1]: 2
counts of [6, 7, 8, 5]: 1