Java Collection Framework - SortedSet Interface

The Collection Framework provides a special Set interface for maintaining elements in a sorted order called SortedSet.

Comparator	comparator() Returns the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
Object	first() Returns the first (lowest) element currently in this sorted set.
SortedSet	headSet(Object toElement) Returns a view of the portion of this sorted set whose elements are strictly less than toElement.
Object	last() Returns the last (highest) element currently in this sorted set.
SortedSet	subSet(Object fromElement, Object toElement) Returns a view of the portion of this sorted set whose elements range from fromElement, inclusive, to toElement, exclusive.
SortedSet	tailSet(Object fromElement) Returns a view of the portion of this sorted set whose elements are greater than or equal to fromElement.

The interface provides access methods to the ends of the set as well to subsets of the set. When working with subsets of the list, changes to the subset are reflected in the source set. In addition changes to the source set are reflected in the subset. This works because subsets are identical by elements at the end point, not indices. In addition , if the formElement is part of the source set , it is part of the subset. However, if the toElement is part of the source ser, it is not part of the subset. If you would like a particular to-element to be in the subset, you must find the next element. In the case of a string, the next element is the same strong with a null character appended (string+”\0”).;

The element added to a SortedSet must either implement Comparable or you must provide a Comparator to the constructor to its implementation class: TreeSet.

This example uses the reverse order Comprator available from the Collection calss.

Comparator comparator= Collections.reverseOrder();
Set reverseSer= new TreeSet(comparator);
revereseSet.add("one");
revereseSet.add("two");
revereseSet.add("three");
revereseSet.add("four");
revereseSet.add("one");
System.out.println(reverseSet);

Output of this program
[two, three, one, four]