November 23, 2013 · 2 min read
**Advise for a fresher**
September 3, 2011 · 1 min read
With **legacy classes** (JDK 1.0 DS) we use [Enumeration](http://way2java.com/collections/enumeration-interface/). With [collections framework](http://way2java.com/collections/java-collections-framework/) classes we use [Iterator](http://way2java.com/collections/iterator-interface/) or [ListIterator](http://way2java.com/collections/listiterator-interface/). As such, with collection classes it is not possible to use Enumeration. To overcome this, the [Collections class](http://way2java.com/collections/collections-api-methods/) comes with **enumeration()** method. It returns collection class elements as an Enumeration. It is a good example on the **interoperability** between legacy and collection classes.
August 30, 2011 · 1 min read
In a data structure (that accepts duplicate elements), an element can exist any number of times as in the case of [ArrayList](http://way2java.com/collections/arraylist-introduction/) etc. The **frequency()** method is useful to find out how many times the same element exist in a data structure.