java.util.SortedMap Maven / Gradle / Ivy
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This work corresponds to the API signatures of JSR 219: Foundation
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*/
package java.util;
/**
* A map that further guarantees that it will be in ascending key order,
* sorted according to the natural ordering of its keys (see the
* Comparable interface), or by a comparator provided at sorted map
* creation time. This order is reflected when iterating over the sorted
* map's collection views (returned by the entrySet, keySet
* and values methods). Several additional operations are provided
* to take advantage of the ordering. (This interface is the map analogue of
* the SortedSet interface.)
*
* All keys inserted into a sorted map must implement the Comparable
* interface (or be accepted by the specified comparator). Furthermore, all
* such keys must be mutually comparable: k1.compareTo(k2) (or
* comparator.compare(k1, k2)) must not throw a
* ClassCastException for any elements k1 and k2 in
* the sorted map. 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 map (whether or not an
* explicit comparator is provided) must be consistent with equals if
* the sorted map is to correctly implement the Map interface. (See
* the Comparable interface or Comparator interface for a
* precise definition of consistent with equals.) This is so because
* the Map interface is defined in terms of the equals
* operation, but a sorted map performs all key comparisons using its
* compareTo (or compare) method, so two keys that are
* deemed equal by this method are, from the standpoint of the sorted map,
* equal. The behavior of a tree map is well-defined even if its
* ordering is inconsistent with equals; it just fails to obey the general
* contract of the Map interface.
*
* All general-purpose sorted map implementation classes should provide four
* "standard" constructors: 1) A void (no arguments) constructor, which
* creates an empty sorted map sorted according to the natural order of
* its keys. 2) A constructor with a single argument of type
* Comparator, which creates an empty sorted map sorted according to
* the specified comparator. 3) A constructor with a single argument of type
* Map, which creates a new map with the same key-value mappings as
* its argument, sorted according to the keys' natural ordering. 4) A
* constructor with a single argument of type sorted map, which creates a new
* sorted map with the same key-value mappings and the same ordering as the
* input sorted map. There is no way to enforce this recommendation (as
* interfaces cannot contain constructors) but the SDK implementation
* (TreeMap) complies.
*
* This interface is a member of the
*
* Java Collections Framework.
*
* @author Josh Bloch
* @version 1.12, 02/02/00
* @see Map
* @see TreeMap
* @see SortedSet
* @see Comparator
* @see Comparable
* @see Collection
* @see ClassCastException
* @since 1.2
*/
public interface SortedMap extends Map
{
/**
* Returns the comparator associated with this sorted map, or
* null if it uses its keys' natural ordering.
*
* @return the comparator associated with this sorted map, or
* null if it uses its keys' natural ordering.
*/
public Comparator comparator();
/**
* Returns a view of the portion of this sorted map whose keys range from
* fromKey, inclusive, to toKey, exclusive. (If
* fromKey and toKey are equal, the returned sorted map
* is empty.) The returned sorted map is backed by this sorted map, so
* changes in the returned sorted map are reflected in this sorted map,
* and vice-versa. The returned Map supports all optional map operations
* that this sorted map supports.
*
* The map returned by this method will throw an
* IllegalArgumentException if the user attempts to insert a key
* 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 key type
* allows for calculation of the successor a given key, merely request the
* subrange from lowEndpoint to successor(highEndpoint).
* For example, suppose that m is a map whose keys are strings.
* The following idiom obtains a view containing all of the key-value
* mappings in m whose keys are between low and
* high, inclusive:
*
*
Map sub = m.subMap(low, high+"\0");
*
* A similarly technique can be used to generate an open range
* (which contains neither endpoint). The following idiom obtains a
* view containing all of the key-value mappings in m whose keys
* are between low and high, exclusive:
*
* Map sub = m.subMap(low+"\0", high);
*
* @param fromKey low endpoint (inclusive) of the subMap.
* @param toKey high endpoint (exclusive) of the subMap.
* @return a view of the specified range within this sorted map.
*
* @throws ClassCastException if fromKey and toKey
* cannot be compared to one another using this map's comparator
* (or, if the map has no comparator, using natural ordering).
* Implementations may, but are not required to, throw this
* exception if fromKey or toKey
* cannot be compared to keys currently in the map.
* @throws IllegalArgumentException if fromKey is greater than
* toKey; or if this map is itself a subMap, headMap,
* or tailMap, and fromKey or toKey are not
* within the specified range of the subMap, headMap, or tailMap.
* @throws NullPointerException if fromKey or toKey is
* null and this sorted map does not tolerate
* null keys.
*/
public SortedMap subMap(Object fromKey, Object toKey);
/**
* Returns a view of the portion of this sorted map whose keys are
* strictly less than toKey. The returned sorted map is backed by this
* sorted map, so changes in the returned sorted map are reflected in this
* sorted map, and vice-versa. The returned map supports all optional map
* operations that this sorted map supports.
*
* The map returned by this method will throw an IllegalArgumentException
* if the user attempts to insert a key 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 key type allows for calculation of the successor a given
* key, merely request a headMap bounded by successor(highEndpoint).
* For example, suppose that suppose that m is a map whose keys
* are strings. The following idiom obtains a view containing all of the
* key-value mappings in m whose keys are less than or equal to
* high:
*
*
Map head = m.headMap(high+"\0");
*
* @param toKey high endpoint (exclusive) of the subMap.
* @return a view of the specified initial range of this sorted map.
* @throws ClassCastException if toKey is not compatible
* with this map's comparator (or, if the map has no comparator,
* if toKey does not implement Comparable).
* Implementations may, but are not required to, throw this
* exception if toKey cannot be compared to keys
* currently in the map.
* @throws IllegalArgumentException if this map is itself a subMap,
* headMap, or tailMap, and toKey is not within the
* specified range of the subMap, headMap, or tailMap.
* @throws NullPointerException if toKey is null and
* this sorted map does not tolerate null keys.
*/
public SortedMap headMap(Object toKey);
/**
* Returns a view of the portion of this sorted map whose keys are greater
* than or equal to fromKey. The returned sorted map is backed
* by this sorted map, so changes in the returned sorted map are reflected
* in this sorted map, and vice-versa. The returned map supports all
* optional map operations that this sorted map supports.
*
* The map returned by this method will throw an
* IllegalArgumentException if the user attempts to insert a key
* 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 tailMap bounded by successor(lowEndpoint).
* For example, suppose that suppose that m is a map whose keys
* are strings. The following idiom obtains a view containing all of the
* key-value mappings in m whose keys are strictly greater than
* low:
*
*
Map tail = m.tailMap(low+"\0");
*
* @param fromKey low endpoint (inclusive) of the tailMap.
* @return a view of the specified final range of this sorted map.
* @throws ClassCastException if fromKey is not compatible
* with this map's comparator (or, if the map has no comparator,
* if fromKey does not implement Comparable).
* Implementations may, but are not required to, throw this
* exception if fromKey cannot be compared to keys
* currently in the map.
* @throws IllegalArgumentException if this map is itself a subMap,
* headMap, or tailMap, and fromKey is not within the
* specified range of the subMap, headMap, or tailMap.
* @throws NullPointerException if fromKey is null and
* this sorted map does not tolerate null keys.
*/
public SortedMap tailMap(Object fromKey);
/**
* Returns the first (lowest) key currently in this sorted map.
*
* @return the first (lowest) key currently in this sorted map.
* @throws NoSuchElementException if this map is empty.
*/
public Object firstKey();
/**
* Returns the last (highest) key currently in this sorted map.
*
* @return the last (highest) key currently in this sorted map.
* @throws NoSuchElementException if this map is empty.
*/
public Object lastKey();
}