OpenJDK 1.23 · java.util.SortedMap · APIdia, the JavaDoc alternative

A Map that further provides a total ordering on its keys. The map is ordered according to the natural ordering of its keys, or by a Comparator typically 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 SortedSet.)

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 keys 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. It is not possible to enforce this recommendation though as required constructors cannot be specified by interfaces. The expected "standard" constructors for all sorted map implementations are:

A void (no arguments) constructor, which creates an empty sorted map sorted according to the natural ordering of its keys.
A constructor with a single argument of type Comparator, which creates an empty sorted map sorted according to the specified comparator.
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.
A constructor with a single argument of type SortedMap, which creates a new sorted map with the same key-value mappings and the same ordering as the input sorted map.

Note

several methods return submaps with restricted key 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 key type allows for calculation of the successor of 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:

  SortedMap<String, V> sub = m.subMap(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 key-value mappings in m whose keys are between low and high, exclusive:

  SortedMap<String, V> sub = m.subMap(low+"\0", high);

This interface is a member of the Java Collections Framework.

Method Summary

Modifier and Type	Method and Description
public Comparator<? super K>	Returns: the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys comparator() Returns the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys.
public Set<Map.Entry<K, V>>	Returns: a set view of the mappings contained in this map, sorted in ascending key order entrySet() Redeclares java.util.Map.entrySet. Returns a `Set` view of the mappings contained in this map.
public K	Returns: the first (lowest) key currently in this map firstKey() Returns the first (lowest) key currently in this map.
public SortedMap<K, V>	Returns: a view of the portion of this map whose keys are strictly less than `toKey` headMap(K high endpoint (exclusive) of the keys in the returned map toKey) Returns a view of the portion of this map whose keys are strictly less than `toKey`.
public Set<K>	Returns: a set view of the keys contained in this map, sorted in ascending order keySet() Redeclares java.util.Map.keySet. Returns a `Set` view of the keys contained in this map.
public K	Returns: the last (highest) key currently in this map lastKey() Returns the last (highest) key currently in this map.
public default V	putFirst(K the key k, V the value v) Overrides default java.util.SequencedMap.putFirst. Throws `UnsupportedOperationException`.
public default V	putLast(K the key k, V the value v) Overrides default java.util.SequencedMap.putLast. Throws `UnsupportedOperationException`.
public default SortedMap<K, V>	Returns: a reverse-ordered view of this map, as a `SortedMap` reversed() Implements java.util.SequencedMap.reversed. Returns a reverse-ordered view of this map.
public SortedMap<K, V>	Returns: a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive subMap(K low endpoint (inclusive) of the keys in the returned map fromKey, K high endpoint (exclusive) of the keys in the returned map toKey) Returns a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive.
public SortedMap<K, V>	Returns: a view of the portion of this map whose keys are greater than or equal to `fromKey` tailMap(K low endpoint (inclusive) of the keys in the returned map fromKey) Returns a view of the portion of this map whose keys are greater than or equal to `fromKey`.
public Collection<V>	Returns: a collection view of the values contained in this map, sorted in ascending key order values() Redeclares java.util.Map.values. Returns a `Collection` view of the values contained in this map.

Inherited from java.util.SequencedMap:: firstEntry lastEntry pollFirstEntry pollLastEntry sequencedEntrySet sequencedKeySet sequencedValues

Method Detail

comparator back to summary

comparator	back to summary
public Comparator<? super K> comparator() Returns the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys. Returns:Comparator<? super K> the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys

public Comparator<? super K> comparator()

Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.

Returns:Comparator<? super K>: the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys

entrySet back to summary

entrySet	back to summary
public Set<Map.Entry<K, V>> entrySet() Redeclares java.util.Map.entrySet. Returns a `Set` view of the mappings contained in this map. The set's iterator returns the entries in ascending key order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own `remove` operation, or through the `setValue` operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the `Iterator.remove`, `Set.remove`, `removeAll`, `retainAll` and `clear` operations. It does not support the `add` or `addAll` operations. Returns:Set<Map.Entry<K, V>> a set view of the mappings contained in this map, sorted in ascending key order

public Set<Map.Entry<K, V>> entrySet()

Redeclares java.util.Map.entrySet.

Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in ascending key order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns:Set<Map.Entry<K, V>>: a set view of the mappings contained in this map, sorted in ascending key order

firstKey	back to summary
public K firstKey() Returns the first (lowest) key currently in this map. Returns:K the first (lowest) key currently in this map Exceptions NoSuchElementException: if this map is empty

firstKey

back to summary

public K firstKey()

Returns the first (lowest) key currently in this map.

Returns:K

the first (lowest) key currently in this map

Exceptions

NoSuchElementException:: if this map is empty

headMap back to summary

headMap	back to summary
public SortedMap<K, V> headMap(K toKey) Returns a view of the portion of this map whose keys are strictly less than `toKey`. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports. The returned map will throw an `IllegalArgumentException` on an attempt to insert a key outside its range. Parameters toKey:K high endpoint (exclusive) of the keys in the returned map Returns:SortedMap<K, V> a view of the portion of this map whose keys are strictly less than `toKey` Exceptions 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. NullPointerException: if `toKey` is null and this map does not permit null keys IllegalArgumentException: if this map itself has a restricted range, and `toKey` lies outside the bounds of the range

public SortedMap<K, V> headMap(K toKey)

Returns a view of the portion of this map whose keys are strictly less than toKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters

toKey:K: high endpoint (exclusive) of the keys in the returned map

Returns:SortedMap<K, V>

a view of the portion of this map whose keys are strictly less than toKey

Exceptions

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.
NullPointerException:: if toKey is null and this map does not permit null keys
IllegalArgumentException:: if this map itself has a restricted range, and toKey lies outside the bounds of the range

keySet back to summary

keySet	back to summary
public Set<K> keySet() Redeclares java.util.Map.keySet. Returns a `Set` view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own `remove` operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the `Iterator.remove`, `Set.remove`, `removeAll`, `retainAll`, and `clear` operations. It does not support the `add` or `addAll` operations. Returns:Set<K> a set view of the keys contained in this map, sorted in ascending order

public Set<K> keySet()

Redeclares java.util.Map.keySet.

Returns a Set view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Returns:Set<K>: a set view of the keys contained in this map, sorted in ascending order

lastKey	back to summary
public K lastKey() Returns the last (highest) key currently in this map. Returns:K the last (highest) key currently in this map Exceptions NoSuchElementException: if this map is empty

lastKey

back to summary

public K lastKey()

Returns the last (highest) key currently in this map.

Returns:K

the last (highest) key currently in this map

Exceptions

NoSuchElementException:: if this map is empty

putFirst back to summary

putFirst	back to summary
public default V putFirst(K k, V v) Overrides default java.util.SequencedMap.putFirst. Throws `UnsupportedOperationException`. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported. Implementation Specification The implementation in this interface always throws `UnsupportedOperationException`. Parameters k:K Doc from java.util.SequencedMap.putFirst. the key v:V Doc from java.util.SequencedMap.putFirst. the value Returns:V Doc from java.util.SequencedMap.putFirst. the value previously associated with k, or null if none Exceptions UnsupportedOperationException: always Since 21

public default V putFirst(K k, V v)

Overrides default java.util.SequencedMap.putFirst.

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Implementation Specification

The implementation in this interface always throws UnsupportedOperationException.

Parameters

k:K

Doc from java.util.SequencedMap.putFirst.

the key

v:V

Doc from java.util.SequencedMap.putFirst.

the value

Returns:V

Doc from java.util.SequencedMap.putFirst.

the value previously associated with k, or null if none

Exceptions

UnsupportedOperationException:: always

Since

putLast back to summary

putLast	back to summary
public default V putLast(K k, V v) Overrides default java.util.SequencedMap.putLast. Throws `UnsupportedOperationException`. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported. Implementation Specification The implementation in this interface always throws `UnsupportedOperationException`. Parameters k:K Doc from java.util.SequencedMap.putLast. the key v:V Doc from java.util.SequencedMap.putLast. the value Returns:V Doc from java.util.SequencedMap.putLast. the value previously associated with k, or null if none Exceptions UnsupportedOperationException: always Since 21

public default V putLast(K k, V v)

Overrides default java.util.SequencedMap.putLast.

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Implementation Specification

The implementation in this interface always throws UnsupportedOperationException.

Parameters

k:K

Doc from java.util.SequencedMap.putLast.

the key

v:V

Doc from java.util.SequencedMap.putLast.

the value

Returns:V

Doc from java.util.SequencedMap.putLast.

the value previously associated with k, or null if none

Exceptions

UnsupportedOperationException:: always

Since

reversed back to summary

reversed	back to summary
public default SortedMap<K, V> reversed() Implements java.util.SequencedMap.reversed. Doc from java.util.SequencedMap.reversed. Returns a reverse-ordered view of this map. The encounter order of mappings in the returned view is the inverse of the encounter order of mappings in this map. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the implementation permits modifications to this view, the modifications "write through" to the underlying map. Changes to the underlying map might or might not be visible in this reversed view, depending upon the implementation. Implementation Specification The implementation in this interface returns a reverse-ordered SortedMap view. The `reversed()` method of the view returns a reference to this SortedMap. Other operations on the view are implemented via calls to public methods on this SortedMap. The exact relationship between calls on the view and calls on this SortedMap is unspecified. However, order-sensitive operations generally behave as if they delegate to the appropriate method with the opposite orientation. For example, calling `firstEntry` on the view might result in a call to `lastEntry` on this SortedMap. Returns:SortedMap<K, V> a reverse-ordered view of this map, as a `SortedMap` Since 21

public default SortedMap<K, V> reversed()

Implements java.util.SequencedMap.reversed.

Doc from java.util.SequencedMap.reversed.

Returns a reverse-ordered view of this map. The encounter order of mappings in the returned view is the inverse of the encounter order of mappings in this map. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the implementation permits modifications to this view, the modifications "write through" to the underlying map. Changes to the underlying map might or might not be visible in this reversed view, depending upon the implementation.

Implementation Specification

The implementation in this interface returns a reverse-ordered SortedMap view. The reversed() method of the view returns a reference to this SortedMap. Other operations on the view are implemented via calls to public methods on this SortedMap. The exact relationship between calls on the view and calls on this SortedMap is unspecified. However, order-sensitive operations generally behave as if they delegate to the appropriate method with the opposite orientation. For example, calling firstEntry on the view might result in a call to lastEntry on this SortedMap.

Returns:SortedMap<K, V>: a reverse-ordered view of this map, as a SortedMap
Since: 21

subMap back to summary

subMap	back to summary
public SortedMap<K, V> subMap(K fromKey, K toKey) Returns a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive. (If `fromKey` and `toKey` are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports. The returned map will throw an `IllegalArgumentException` on an attempt to insert a key outside its range. Parameters fromKey:K low endpoint (inclusive) of the keys in the returned map toKey:K high endpoint (exclusive) of the keys in the returned map Returns:SortedMap<K, V> a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive Exceptions 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. NullPointerException: if `fromKey` or `toKey` is null and this map does not permit null keys IllegalArgumentException: if `fromKey` is greater than `toKey`; or if this map itself has a restricted range, and `fromKey` or `toKey` lies outside the bounds of the range

public SortedMap<K, V> subMap(K fromKey, K toKey)

Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters

fromKey:K: low endpoint (inclusive) of the keys in the returned map
toKey:K: high endpoint (exclusive) of the keys in the returned map

Returns:SortedMap<K, V>

a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive

Exceptions

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.
NullPointerException:: if fromKey or toKey is null and this map does not permit null keys
IllegalArgumentException:: if fromKey is greater than toKey; or if this map itself has a restricted range, and fromKey or toKey lies outside the bounds of the range

tailMap back to summary

tailMap	back to summary
public SortedMap<K, V> tailMap(K fromKey) Returns a view of the portion of this map whose keys are greater than or equal to `fromKey`. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports. The returned map will throw an `IllegalArgumentException` on an attempt to insert a key outside its range. Parameters fromKey:K low endpoint (inclusive) of the keys in the returned map Returns:SortedMap<K, V> a view of the portion of this map whose keys are greater than or equal to `fromKey` Exceptions 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. NullPointerException: if `fromKey` is null and this map does not permit null keys IllegalArgumentException: if this map itself has a restricted range, and `fromKey` lies outside the bounds of the range

public SortedMap<K, V> tailMap(K fromKey)

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

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters

fromKey:K: low endpoint (inclusive) of the keys in the returned map

Returns:SortedMap<K, V>

a view of the portion of this map whose keys are greater than or equal to fromKey

Exceptions

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.
NullPointerException:: if fromKey is null and this map does not permit null keys
IllegalArgumentException:: if this map itself has a restricted range, and fromKey lies outside the bounds of the range

values back to summary

values	back to summary
public Collection<V> values() Redeclares java.util.Map.values. Returns a `Collection` view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own `remove` operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the `Iterator.remove`, `Collection.remove`, `removeAll`, `retainAll` and `clear` operations. It does not support the `add` or `addAll` operations. Returns:Collection<V> a collection view of the values contained in this map, sorted in ascending key order

public Collection<V> values()

Redeclares java.util.Map.values.

Returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Returns:Collection<V>: a collection view of the values contained in this map, sorted in ascending key order

public Interface SortedMap<K, V>

Method Summary

Method Detail