Question

I have java.util.LinkedHashMap with Integer as Key and Character as Value. I know the key of the element i want to access. In addition to the element value for the key, i also want to retrieve the next 3 element values so that i can append all the 4 element values and form a string with 4 chars. I am asking for something like how we will do in a java.util.List. Is this feasible by any means in a Map/ordered map? Please suggest any other data structure that can help me achieve this. I am using Java 6.

Answer 1

java.util.SortedMap has the methods subMap(fromKey, toKey) and tailMap(fromKey).

You can use the first one if you know the last key you want, but in your case since you want a fixed number of elements, you should try

SortedMap<Integer, Character> tail = l.tailMap(yourKey);
int cnt = 0;
List<Char> result = new ArrayList<Character>();
for (Iterator<Entry<Integer, Character>> it = tail.iterator(); it.hasNext() && cnt < 3; cnt++) {
  reasult.add(it.next());
}

Note that if the values of the map were not immutable, changes in the list would be reflected in the map and vice versa, since I added the reference of the element to the list(to avoid this you should add a copy of the object in the list).