How to sort HashMap of arrays by integer key Java

You don't need the (Comparator<? super Integer>) part for your TreeMap. Also you have used String instead of String[] in your declaration. This code will work:

SortedMap<Integer, String[]> sortedMap = new TreeMap<Integer, String[]>(Htab);

Or alternatively you can declare Htab as a TreeMap instead of a HashMap to begin with.

Just create the TreeMap with the HashMap as a parameter.

public void test() {
    Map<Integer, String[]> htab = new HashMap<>();
    String[] a = {"a", "3", "5", "10", "0"};
    htab.put(21, a);
    String[] b = {"b", "3", "5", "10", "0"};
    htab.put(210, b);
    String[] c = {"c", "3", "5", "10", "0"};
    htab.put(2, c);
    Map<Integer, String[]> sorted = new TreeMap<>(htab);
    System.out.println(htab);
    System.out.println(sorted);
}

You can use a TreeMap as per the comment written by jesper.

    Map<Integer, String[]> map = new TreeMap<Integer, String[]>();
    map.put(21, new String[] {"abc","bcde", "regweger"});
    map.put(43, new String[] {"dbc","bgercde", "reggweer"});
    map.put(31, new String[] {"afbc","bcdrge", "rewgwger"});
    map.put(5, new String[] {"abgc","bcdee", "regwesgr"});
    map.put(98, new String[] {"abhhc","bc3gde", "regrer"});
    map.put(11, new String[] {"awqbc","bc33de", "frgeger"});

    System.out.println(map.toString());

You will find the to string prints out the elements in ascending order of key value.

If you want to sort the keys you may use a TreeSet or a TreeMap as follows. The keys are naturally sorted, i.e. the sorting is defined by the Integer class.

Map<Integer, String[]> map = new HashMap<>();

Set<Integer> naturallySortedKeys = new TreeSet<>(map.keySet());
Map<Integer, String[]> naturallySortedMap = new TreeMap<>(map);