Partition { public void order() { Collections.sort(cells, new Comparator<SortedSet<Integer>>() { @Override public int compare(SortedSet<Integer> cellA, SortedSet<Integer> cellB) { return cellA.first().compareTo(cellB.first()); } }); } Partition();  Partition(Partition other);  Partition(int[][] cellData); static Partition unit(int size); @Override boolean equals(Object o); @Override int hashCode(); int size(); int numberOfElements(); boolean isDiscrete(); Permutation toPermutation(); boolean inOrder(); int getFirstInCell(int cellIndex); SortedSet<Integer> getCell(int cellIndex); Partition splitBefore(int cellIndex, int splitElement); Partition splitAfter(int cellIndex, int splitElement); Permutation setAsPermutation(int upTo); boolean isDiscreteCell(int cellIndex); int getIndexOfFirstNonDiscreteCell(); void addSingletonCell(int element); void removeCell(int index); void addCell(int... elements); void addCell(Collection<Integer> elements); void addToCell(int index, int element); void insertCell(int index, SortedSet<Integer> cell); SortedSet<Integer> copyBlock(int cellIndex); void order(); boolean inSameCell(int elementI, int elementJ); @Override String toString(); static Partition fromString(String strForm);  }
@Test public void orderTest() { Partition p = new Partition(new int[][]{{1, 3}, {0, 2}}); p.order(); SortedSet<Integer> cell0 = p.getCell(0); SortedSet<Integer> cell1 = p.getCell(1); Assert.assertTrue(cell0.first() < cell1.first()); Assert.assertTrue(cell0.last() < cell1.last()); }