java.util.SortedSet Maven / Gradle / Ivy
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package java.util;
/**
* A {@link Set} that further provides a total ordering on its elements.
* The elements are ordered using their {@linkplain Comparable natural
* ordering}, or by a {@link Comparator} typically provided at sorted
* set creation time. The set's iterator will traverse the set in
* ascending element order. Several additional operations are provided
* to take advantage of the ordering. (This interface is the set
* analogue of {@link SortedMap}.)
*
* All elements inserted into a 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 ordering 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 natural ordering of the elements.
* 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.
*
*
Note: several methods return subsets with restricted ranges.
* Such ranges are half-open, that is, they include their low
* endpoint but not their high endpoint (where applicable).
* If you need a closed range (which includes both endpoints), and
* the element type allows for calculation of the successor of 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<String> 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<String> sub = s.subSet(low+"\0", high);
*
* This interface is a member of the
*
* Java Collections Framework.
*
* @param the type of elements maintained by this set
*
* @author Josh Bloch
* @see Set
* @see TreeSet
* @see SortedMap
* @see Collection
* @see Comparable
* @see Comparator
* @see ClassCastException
* @since 1.2
*/
public interface SortedSet extends Set {
/**
* Returns the comparator used to order the elements in this set,
* or null if this set uses the {@linkplain Comparable
* natural ordering} of its elements.
*
* @return the comparator used to order the elements in this set,
* or null if this set uses the natural ordering
* of its elements
*/
Comparator comparator();
/**
* Returns a view of the portion of this set whose elements range
* from fromElement, inclusive, to toElement,
* exclusive. (If fromElement and toElement are
* equal, the returned set is empty.) The returned set is backed
* by this set, so changes in the returned set are reflected in
* this set, and vice-versa. The returned set supports all
* optional set operations that this set supports.
*
* The returned set will throw an IllegalArgumentException
* on an attempt to insert an element outside its range.
*
* @param fromElement low endpoint (inclusive) of the returned set
* @param toElement high endpoint (exclusive) of the returned set
* @return a view of the portion of this set whose elements range from
* fromElement, inclusive, to toElement, exclusive
* @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.
* @throws NullPointerException if fromElement or
* toElement is null and this set does not permit null
* elements
* @throws IllegalArgumentException if fromElement is
* greater than toElement; or if this set itself
* has a restricted range, and fromElement or
* toElement lies outside the bounds of the range
*/
SortedSet subSet(E fromElement, E toElement);
/**
* Returns a view of the portion of this set whose elements are
* strictly less than toElement. The returned set is
* backed by this set, so changes in the returned set are
* reflected in this set, and vice-versa. The returned set
* supports all optional set operations that this set supports.
*
* The returned set will throw an IllegalArgumentException
* on an attempt to insert an element outside its range.
*
* @param toElement high endpoint (exclusive) of the returned set
* @return a view of the portion of this set whose elements are strictly
* less than toElement
* @throws ClassCastException if toElement is not compatible
* with this set's comparator (or, if the set has no comparator,
* if toElement does not implement {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if toElement cannot be compared to elements
* currently in the set.
* @throws NullPointerException if toElement is null and
* this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and toElement lies outside the
* bounds of the range
*/
SortedSet headSet(E toElement);
/**
* Returns a view of the portion of this set whose elements are
* greater than or equal to fromElement. The returned
* set is backed by this set, so changes in the returned set are
* reflected in this set, and vice-versa. The returned set
* supports all optional set operations that this set supports.
*
* The returned set will throw an IllegalArgumentException
* on an attempt to insert an element outside its range.
*
* @param fromElement low endpoint (inclusive) of the returned set
* @return a view of the portion of this set whose elements are greater
* than or equal to fromElement
* @throws ClassCastException if fromElement is not compatible
* with this set's comparator (or, if the set has no comparator,
* if fromElement does not implement {@link Comparable}).
* Implementations may, but are not required to, throw this
* exception if fromElement cannot be compared to elements
* currently in the set.
* @throws NullPointerException if fromElement is null
* and this set does not permit null elements
* @throws IllegalArgumentException if this set itself has a
* restricted range, and fromElement lies outside the
* bounds of the range
*/
SortedSet tailSet(E fromElement);
/**
* Returns the first (lowest) element currently in this set.
*
* @return the first (lowest) element currently in this set
* @throws NoSuchElementException if this set is empty
*/
E first();
/**
* Returns the last (highest) element currently in this set.
*
* @return the last (highest) element currently in this set
* @throws NoSuchElementException if this set is empty
*/
E last();
}