java.util
public interface SortedSet<E> extends Set<E>
All elements inserted into an sorted set must implement the Comparable interface (or be accepted by the specified Comparator). Furthermore, all such elements must be mutually comparable: e1.compareTo(e2) (or comparator.compare(e1, e2)) must not throw a ClassCastException for any elements e1 and e2 in the sorted set. Attempts to violate this restriction will cause the offending method or constructor invocation to throw a ClassCastException.
Note that the ordering maintained by a sorted set (whether or not an explicit comparator is provided) must be consistent with equals if the sorted set is to correctly implement the Set interface. (See the Comparable interface or Comparator interface for a precise definition of consistent with equals.) This is so because the Set interface is defined in terms of the equals operation, but a sorted set performs all element comparisons using its compareTo (or compare) method, so two elements that are deemed equal by this method are, from the standpoint of the sorted set, equal. The behavior of a sorted set is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Set interface.
All general-purpose sorted set implementation classes should provide four "standard" constructors: 1) A void (no arguments) constructor, which creates an empty sorted set sorted according to the natural order of its elements. 2) A constructor with a single argument of type Comparator, which creates an empty sorted set sorted according to the specified comparator. 3) A constructor with a single argument of type Collection, which creates a new sorted set with the same elements as its argument, sorted according to the elements' natural ordering. 4) A constructor with a single argument of type SortedSet, which creates a new sorted set with the same elements and the same ordering as the input sorted set. There is no way to enforce this recommendation (as interfaces cannot contain constructors) but the SDK implementation (the TreeSet class) complies.
This interface is a member of the Java Collections Framework.
Since: 1.2
Version: 1.22, 06/22/03
See Also: Set TreeSet SortedMap Collection Comparable Comparator java.lang.ClassCastException
| Method Summary | |
|---|---|
| Comparator<? super E> | comparator()
Returns the comparator associated with this sorted set, or
null if it uses its elements' natural ordering.
|
| E | first()
Returns the first (lowest) element currently in this sorted set.
|
| SortedSet<E> | headSet(E toElement)
Returns a view of the portion of this sorted set whose elements are
strictly less than toElement. |
| E | last()
Returns the last (highest) element currently in this sorted set.
|
| SortedSet<E> | subSet(E fromElement, E toElement)
Returns a view of the portion of this sorted set whose elements range
from fromElement, inclusive, to toElement, exclusive.
|
| SortedSet<E> | tailSet(E fromElement)
Returns a view of the portion of this sorted set whose elements are
greater than or equal to fromElement. |
Returns: the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
Returns: the first (lowest) element currently in this sorted set.
Throws: NoSuchElementException sorted set is empty.
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert a element outside the specified range.
Note: this method always returns a view that does not contain its (high) endpoint. If you need a view that does contain this endpoint, and the element type allows for calculation of the successor a given value, merely request a headSet bounded by successor(highEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s that are less than or equal to high:
SortedSet head = s.headSet(high+"\0");
Parameters: toElement high endpoint (exclusive) of the headSet.
Returns: a view of the specified initial range of this sorted set.
Throws: ClassCastException if toElement is not compatible with this set's comparator (or, if the set has no comparator, if toElement does not implement Comparable). Implementations may, but are not required to, throw this exception if toElement cannot be compared to elements currently in the set. NullPointerException if toElement is null and this sorted set does not tolerate null elements. IllegalArgumentException if this set is itself a subSet, headSet, or tailSet, and toElement is not within the specified range of the subSet, headSet, or tailSet.
Returns: the last (highest) element currently in this sorted set.
Throws: NoSuchElementException sorted set is empty.
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert a element outside the specified range.
Note: this method always returns a half-open range (which includes its low endpoint but not its high endpoint). If you need a closed range (which includes both endpoints), and the element type allows for calculation of the successor a given value, merely request the subrange from lowEndpoint to successor(highEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s from low to high, inclusive:
SortedSet sub = s.subSet(low, high+"\0");A similar technique can be used to generate an open range (which contains neither endpoint). The following idiom obtains a view containing all of the Strings in s from low to high, exclusive:
SortedSet sub = s.subSet(low+"\0", high);
Parameters: fromElement low endpoint (inclusive) of the subSet. toElement high endpoint (exclusive) of the subSet.
Returns: a view of the specified range within this sorted set.
Throws: ClassCastException if fromElement and toElement cannot be compared to one another using this set's comparator (or, if the set has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromElement or toElement cannot be compared to elements currently in the set. IllegalArgumentException if fromElement is greater than toElement; or if this set is itself a subSet, headSet, or tailSet, and fromElement or toElement are not within the specified range of the subSet, headSet, or tailSet. NullPointerException if fromElement or toElement is null and this sorted set does not tolerate null elements.
The sorted set returned by this method will throw an IllegalArgumentException if the user attempts to insert a element outside the specified range.
Note: this method always returns a view that contains its (low) endpoint. If you need a view that does not contain this endpoint, and the element type allows for calculation of the successor a given value, merely request a tailSet bounded by successor(lowEndpoint). For example, suppose that s is a sorted set of strings. The following idiom obtains a view containing all of the strings in s that are strictly greater than low:
SortedSet tail = s.tailSet(low+"\0");
Parameters: fromElement low endpoint (inclusive) of the tailSet.
Returns: a view of the specified final range of this sorted set.
Throws: ClassCastException if fromElement is not compatible with this set's comparator (or, if the set has no comparator, if fromElement does not implement Comparable). Implementations may, but are not required to, throw this exception if fromElement cannot be compared to elements currently in the set. NullPointerException if fromElement is null and this sorted set does not tolerate null elements. IllegalArgumentException if this set is itself a subSet, headSet, or tailSet, and fromElement is not within the specified range of the subSet, headSet, or tailSet.