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This is Analogous to Java's LinkedHashMap. Just create a LinkedList structure and attach new nodes (elements) as they are added, it's going to be in added order.

public class OrderedHashtable {

	private Hashtable<String, String> internalHashTable = new Hashtable<String, String>();
	private List<String> orderedKeyList = new ArrayList<String>();

	public void addToHashTable(String key, String value) {
		orderedKeyList.add(key);
		internalHashTable.put(key, value);
	}

	public String getValue(String key) {
		return internalHashTable.get(key);
	}

	public List<String> getKeys() {
		return orderedKeyList;
	}

}

public static void main(String[] args) {

		OrderedHashtable orderedHashtable = new OrderedHashtable();
		orderedHashtable.addToHashTable("a", "1");
		orderedHashtable.addToHashTable("b", "2");
		orderedHashtable.addToHashTable("c", "3");
		orderedHashtable.addToHashTable("e", "6");
		
		orderedHashtable.addToHashTable("f", "22");
		orderedHashtable.addToHashTable("g", "100");
		
		List<String> keys = orderedHashtable.getKeys();
		for (String key : keys) {
			System.out.println(orderedHashtable.getValue(key));
		}
	}

you have to do using hashtable itself

In LinkedHashMap implementation doubly linked list is used to maintain the insertion order. This doubly linked list is different from linked list maintained by each bucket location in hashmap.

LinkedHashMap lists the elements in the order they were inserted.
TreeHashMap iterates over the elements in their natural order.

store the keys dynamically in a array as they are added

Can you explain the question? Is it asking about a method to do this, using an extra structure?

create Map<String, String> treeMap = new TreeMap<String, String>(unsortMap);
it will create sorted map from unsorted.
Please let me know if any issue concern.

We cannot retrieve the elements in the hashtable in the same order as you have inserted. Because the basic design of hashtable is to provide searching in O(1) time.

k

hi