SortedSet (Java 2 Platform SE 5.0) (original) (raw)

java.util

Interface SortedSet

All Superinterfaces:

All Known Implementing Classes:

public interface SortedSet

extends Set

A set that further guarantees that its iterator will traverse the set in ascending element order, sorted according to the natural ordering of its elements (see Comparable), or by a Comparator provided at sorted set creation time. Several additional operations are provided to take advantage of the ordering. (This interface is the set analogue of SortedMap.)

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 aClassCastException 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 aClassCastException.

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 itscompareTo (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 typeComparator, which creates an empty sorted set sorted according to the specified comparator. 3) A constructor with a single argument of typeCollection, 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 JDK implementation (theTreeSet class) complies.

This interface is a member of the Java Collections Framework.

Since:

1.2

Method Summary
Comparator<? super E>	comparator() Returns the comparator associated with this sorted set, ornull 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](../../java/util/SortedSet.html#subSet%28E, E%29)(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.

Methods inherited from interface java.util.Set
add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

Method Detail

comparator

Comparator<? super E> comparator()

Returns the comparator associated with this sorted set, ornull if it uses its elements' natural ordering.

Returns:

the comparator associated with this sorted set, ornull if it uses its elements' natural ordering.

subSet

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. (If fromElement and toElement are equal, the returned sorted set is empty.) The returned sorted set is backed by this sorted set, so changes in the returned sorted set are reflected in this sorted set, and vice-versa. The returned sorted set supports all optional set operations that this sorted set supports.

The sorted set returned by this method will throw anIllegalArgumentException 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 tosuccessor(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 tohigh, 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 tohigh, 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](../../java/lang/ClassCastException.html "class in java.lang") - if fromElement andtoElement 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 ortoElement cannot be compared to elements currently in the set.

[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang") - if fromElement is greater thantoElement; 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](../../java/lang/NullPointerException.html "class in java.lang") - if fromElement ortoElement is null and this sorted set does not tolerate null elements.

headSet

SortedSet<E> headSet(E toElement)

Returns a view of the portion of this sorted set whose elements are strictly less than toElement. The returned sorted set is backed by this sorted set, so changes in the returned sorted set are reflected in this sorted set, and vice-versa. The returned sorted set supports all optional set operations.

The sorted set returned by this method will throw anIllegalArgumentException 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 bysuccessor(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](../../java/lang/ClassCastException.html "class in java.lang") - 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](../../java/lang/NullPointerException.html "class in java.lang") - if toElement is null and this sorted set does not tolerate null elements.

[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang") - if this set is itself a subSet, headSet, or tailSet, and toElement is not within the specified range of the subSet, headSet, or tailSet.

tailSet

SortedSet<E> tailSet(E fromElement)

Returns a view of the portion of this sorted set whose elements are greater than or equal to fromElement. The returned sorted set is backed by this sorted set, so changes in the returned sorted set are reflected in this sorted set, and vice-versa. The returned sorted set supports all optional set operations.

The sorted set returned by this method will throw anIllegalArgumentException 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 ins 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](../../java/lang/ClassCastException.html "class in java.lang") - 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](../../java/lang/NullPointerException.html "class in java.lang") - if fromElement is null and this sorted set does not tolerate null elements.

[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang") - if this set is itself a subSet, headSet, or tailSet, and fromElement is not within the specified range of the subSet, headSet, or tailSet.

first

E first()

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

Returns:

the first (lowest) element currently in this sorted set.

Throws:

[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - sorted set is empty.

last

E last()

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

Returns:

the last (highest) element currently in this sorted set.

Throws:

[NoSuchElementException](../../java/util/NoSuchElementException.html "class in java.util") - sorted set is empty.

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.