How do I sort Hashtable keys?

How do I sort Hashtable keys?

You have a hashtable of keys and values, and want to get the list of values that result from sorting the keys in order. To sort a hashtable, use the GetEnumerator() method on the hashtable to gain access to its individual elements. Then use the SortObject cmdlet to sort by Name or Value.

Can Hashtable be sorted?

Before moving forward, we need to understand that it is not possible to sort a Hashtable since the data is stored by the hashcode of the key, not by the index . So to sort the data of a Hashtable, we need to have a sortable object like an array or an ArrayList. Sorting has to be done on Key or Value.

Is Java Hashtable sorted?

A Hashtable has no predictable iteration order, and cannot be sorted. If you only want predictable iteration order you should use a LinkedHashMap . If you want to be able to sort your Map , you should use a TreeMap . Hashtable is a legacy collection which was replaced by Java 1.2 collections in 1998.

Does Hashtable maintain order?

Hashtable doesn’t preserve the insertion order, neither it sorts the inserted data based on keys or values. Which means no matter what keys & values you insert into Hashtable, the result would not be in any particular order. As you can see that the output key-value pairs are in random order.

Does HashMap maintain insertion order?

HashMap does not maintains insertion order in java. Hashtable does not maintains insertion order in java. LinkedHashMap maintains insertion order in java. TreeMap is sorted by natural order of keys in java.

Can I sort a HashMap?

HashMap is not meant to keep entries in sorted order, but if you have to sort HashMap based upon keys or values, you can do that in Java. Sorting HashMap on keys is quite easy, all you need to do is to create a TreeMap by copying entries from HashMap. This is similar to how you sort an ArrayList in Java.

What is the difference between HashMap and Hashtable?

HashMap is non-synchronized. It is not thread-safe and can’t be shared between many threads without proper synchronization code whereas Hashtable is synchronized. HashMap allows one null key and multiple null values whereas Hashtable doesn’t allow any null key or value.

Does list maintain insertion order?

1) List is an ordered collection it maintains the insertion order, which means upon displaying the list content it will display the elements in the same order in which they got inserted into the list. Set is an unordered collection, it doesn’t maintain any order.

Will ArrayList maintain insertion order?

Yes, ArrayList is an ordered collection and it maintains the insertion order.

Does HashMap maintain order of insertion?

” HashMap does not preserve insertion order “. HashMap is collection of Key and Value but HashMap does not give guaranty that insertion order will preserve.

Does HashMap sort automatically?

No, HashMap s don’t sort their keys automatically. You want a TreeMap for sorting the keys, or a LinkedHashMap to retain the insertion order.

Which is better Hashtable or HashMap?

Performance : HashMap is much faster and uses less memory than Hashtable as former is unsynchronized . Unsynchronized objects are often much better in performance in compare to synchronized object like Hashtable in single threaded environment.