Question

I have an ArrayList of HashMap. Each HashMap contains many key-value-pairs. I want to sort the ArrayList by the value of the key distance in the HashMap.

ArrayList<HashMap<String, String>> arrayListHashMap = 
    new ArrayList<HashMap<String, String>>();

{
    HashMap hashMap = new HashMap<String, Object>();
    hashMap.put("key", "A key");
    hashMap.put("value", "B value");
    hashMap.put("distance", 2536);

    arrayListHashMap.add(hashMap);
}

{
    HashMap hashMap = new HashMap<String, String>();
    hashMap.put("key", "B key");
    hashMap.put("value", "A value");
    hashMap.put("distance", 2539);
    arrayListHashMap.add(hashMap);
}

Answer 1

You can try to sort with a custom comparator:

Collections.sort(arrayListHashMap, new Comparator<HashMap<String, String>>() {

    @Override
    public int compare(HashMap<String, String> m1, HashMap<String, String> m2) {
        return Integer.valueOf(m1.get("distance")).compareTo(Integer.valueOf(m2.get("distance")));
    }
});

Note that I assumed all your values are strings which is not the case in your example (distance is an int value).