sort counter by value

public class Solution {
public List<Integer> topKFrequent(int[] nums, int k) {
List<Integer> result = new ArrayList<Integer>();
HashMap<Integer, Integer> counter = new HashMap<Integer, Integer>();
for(int i: nums){
if(counter.containsKey(i)){
counter.put(i, counter.get(i)+1);
}else{
counter.put(i, 1);
}
}
TreeMap<Integer, Integer> sortedMap = new TreeMap<Integer, Integer>(new
ValueComparator(counter));
sortedMap.putAll(counter);
int i=0;
for(Map.Entry<Integer, Integer> entry: sortedMap.entrySet()){
result.add(entry.getKey());
i++;
if(i==k)
break;
}
return result;
}
}
class ValueComparator implements Comparator<Integer>{
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
public ValueComparator(HashMap<Integer, Integer> m){
map.putAll(m);
}
public int compare(Integer i1, Integer i2){
int diff = map.get(i2)-map.get(i1);
if(diff==0){
return 1;
}else{
return diff;
}
}
}