How to sort a HashMap in Java [duplicate]

Answer 1

A proper answer.

HashMap map = new HashMap();

ArrayList sortedKeys = new ArrayList(map.keySet());
Collections.sort(sortedKeys, new Comparator() {
  @Override
  public int compare(Integer a, Integer b) {
    return a.compareTo(b);
  }
});

for (Integer key: sortedKeys) {
  //map.get(key);
}

Note that HashMap itself cannot maintain sorting, as other answers have pointed out. It's a hash map, and hashed values are unsorted. You can thus either sort the keys when you need to and then access the values in order, as I demonstrated above, or you can find a different collection to store your data, like an ArrayList of Pairs/Tuples, such as the Pair found in Apache Commons:

https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/tuple/Pair.html