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**All Superinterfaces:**- Collection<E>, Iterable<E>, Set<E>

`public interface `**SortedSet<E>**

`extends Set<E>`

A set which guarantees its iteration order. The elements in the set
are related by the *natural ordering* if they are Comparable, or
by the provided Comparator. Additional operations take advantage of
the sorted nature of the set.

All elements entered in the set must be mutually comparable; in other words,
`k1.compareTo(k2)`

or `comparator.compare(k1, k2)`

must not throw a ClassCastException. The ordering must be *consistent
with equals* (see `Comparator`

for this definition), if the
set is to obey the general contract of the Set interface. If not,
the results are well-defined, but probably not what you wanted.

It is recommended that all implementing classes provide four constructors: 1) one that takes no arguments and builds an empty set sorted by natural order of the elements; 2) one that takes a Comparator for the sorting order; 3) one that takes a Set and sorts according to the natural order of its elements; and 4) one that takes a SortedSet and sorts by the same comparator. Unfortunately, the Java language does not provide a way to enforce this.

**Since:**- 1.2

**See Also:**`Set`

,`TreeSet`

,`SortedMap`

,`Collection`

,`Comparable`

,`Comparator`

,`ClassCastException`

## Method Summary

`E`

`first()`

- Returns the first (lowest sorted) element in the set.

`SortedSet`

`headSet(E toElement)`

- Returns a view of the portion of the set strictly less than toElement.

`E`

`last()`

- Returns the last (highest sorted) element in the set.

`SortedSet`

`subSet(E fromElement, E toElement)`

- Returns a view of the portion of the set greater than or equal to fromElement, and strictly less than toElement.

`Comparator`

`super E> comparator()`

- Returns the comparator used in sorting this set, or null if it is the elements' natural ordering.

`SortedSet`

`tailSet(E fromElement)`

- Returns a view of the portion of the set greater than or equal to fromElement.

### Methods inherited from interface java.util.Collection<E>

`T[] toArray`

,`add`

,`addAll`

,`clear`

,`contains`

,`containsAll`

,`equals`

,`hashCode`

,`isEmpty`

,`iterator`

,`remove`

,`removeAll`

,`retainAll`

,`size`

,`toArray`

### Methods inherited from interface java.lang.Iterable<E>

`iterator`

### Methods inherited from interface java.util.Set<E>

`T[] toArray`

,`add`

,`addAll`

,`clear`

,`contains`

,`containsAll`

,`equals`

,`hashCode`

,`isEmpty`

,`iterator`

,`remove`

,`removeAll`

,`retainAll`

,`size`

,`toArray`

public E first()

Returns the first (lowest sorted) element in the set.

Returns:- the first element

Throws:`NoSuchElementException`

- if the set is empty.

public SortedSetheadSet(E toElement)

Returns a view of the portion of the set strictly less than toElement. The view is backed by this set, so changes in one show up in the other. The subset supports all optional operations of the original.The returned set throws an IllegalArgumentException any time an element is used which is out of the range of toElement. Note that the endpoint, toElement, is not included; if you want this value included, pass its successor object in to toElement. For example, for Integers, you could request

`headSet(new Integer(limit.intValue() + 1))`

.

Parameters:`toElement`

- the exclusive upper range of the subset

Returns:- the subset

Throws:`ClassCastException`

- if toElement is not comparable to the set contents`IllegalArgumentException`

- if this is a subSet, and toElement is out of range`NullPointerException`

- if toElement is null but the set does not allow null elements

public E last()

Returns the last (highest sorted) element in the set.

Returns:- the last element

Throws:`NoSuchElementException`

- if the set is empty.

public SortedSetsubSet(E fromElement, E toElement)

Returns a view of the portion of the set greater than or equal to fromElement, and strictly less than toElement. The view is backed by this set, so changes in one show up in the other. The subset supports all optional operations of the original.The returned set throws an IllegalArgumentException any time an element is used which is out of the range of fromElement and toElement. Note that the lower endpoint is included, but the upper is not; if you want to change the inclusion or exclusion of an endpoint, pass its successor object in instead. For example, for Integers, you can request

`subSet(new Integer(lowlimit.intValue() + 1), new Integer(highlimit.intValue() + 1))`

to reverse the inclusiveness of both endpoints.

Parameters:`fromElement`

- the inclusive lower range of the subset`toElement`

- the exclusive upper range of the subset

Returns:- the subset

Throws:`ClassCastException`

- if fromElement or toElement is not comparable to the set contents`IllegalArgumentException`

- if this is a subSet, and fromElement or toElement is out of range`NullPointerException`

- if fromElement or toElement is null but the set does not allow null elements

public Comparatorsuper E> comparator()

Returns the comparator used in sorting this set, or null if it is the elements' natural ordering.

Returns:- the sorting comparator

public SortedSettailSet(E fromElement)

Returns a view of the portion of the set greater than or equal to fromElement. The view is backed by this set, so changes in one show up in the other. The subset supports all optional operations of the original.The returned set throws an IllegalArgumentException any time an element is used which is out of the range of fromElement. Note that the endpoint, fromElement, is included; if you do not want this value to be included, pass its successor object in to fromElement. For example, for Integers, you could request

`tailSet(new Integer(limit.intValue() + 1))`

.

Parameters:`fromElement`

- the inclusive lower range of the subset

Returns:- the subset

Throws:`ClassCastException`

- if fromElement is not comparable to the set contents`IllegalArgumentException`

- if this is a subSet, and fromElement is out of range`NullPointerException`

- if fromElement is null but the set does not allow null elements

SortedSet.java -- A set that makes guarantees about the order of its
elements
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