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Top Description Methods
java.util

public Interface NavigableMap<K, V>

extends SortedMap<K, V>
Known Direct Subinterfaces
java.util.concurrent.ConcurrentNavigableMap
Known Direct Implementers
java.util.TreeMap, java.util.TreeMap.NavigableSubMap, java.util.Collections.UnmodifiableNavigableMap, java.util.Collections.SynchronizedNavigableMap, java.util.Collections.CheckedNavigableMap
Type Parameters
<K>
the type of keys maintained by this map
<V>
the type of mapped values
A SortedMap extended with navigation methods returning the closest matches for given search targets. Methods lowerEntry, floorEntry, ceilingEntry, and higherEntry return Map.Entry objects associated with keys respectively less than, less than or equal, greater than or equal, and greater than a given key, returning null if there is no such key. Similarly, methods lowerKey, floorKey, ceilingKey, and higherKey return only the associated keys. All of these methods are designed for locating, not traversing entries.

A NavigableMap may be accessed and traversed in either ascending or descending key order. The descendingMap method returns a view of the map with the senses of all relational and directional methods inverted. The performance of ascending operations and views is likely to be faster than that of descending ones. Methods subMap(K, boolean, K, boolean), headMap(K, boolean), and tailMap(K, boolean) differ from the like-named SortedMap methods in accepting additional arguments describing whether lower and upper bounds are inclusive versus exclusive. Submaps of any NavigableMap must implement the NavigableMap interface.

This interface additionally defines methods firstEntry, pollFirstEntry, lastEntry, and pollLastEntry that return and/or remove the least and greatest mappings, if any exist, else returning null.

The methods ceilingEntry, firstEntry, floorEntry, higherEntry, lastEntry, lowerEntry, pollFirstEntry, and pollLastEntry return Map.Entry instances that represent snapshots of mappings as of the time of the call. They do not support mutation of the underlying map via the optional setValue method.

Methods subMap(K, K), headMap(K), and tailMap(K) are specified to return SortedMap to allow existing implementations of SortedMap to be compatibly retrofitted to implement NavigableMap, but extensions and implementations of this interface are encouraged to override these methods to return NavigableMap. Similarly, keySet() can be overridden to return NavigableSet.

This interface is a member of the Java Collections Framework.

Authors
Doug Lea, Josh Bloch
Since
1.6

Method Summary

Modifier and TypeMethod and Description
public Map.Entry<K, V>

Returns:

an entry with the least key greater than or equal to key, or null if there is no such key
ceilingEntry(K
the key
key)

Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such key.

public K

Returns:

the least key greater than or equal to key, or null if there is no such key
ceilingKey(K
the key
key)

Returns the least key greater than or equal to the given key, or null if there is no such key.

public NavigableSet<K>

Returns:

a reverse order navigable set view of the keys in this map
descendingKeySet()

Returns a reverse order NavigableSet view of the keys contained in this map.

public NavigableMap<K, V>

Returns:

a reverse order view of this map
descendingMap()

Returns a reverse order view of the mappings contained in this map.

public Map.Entry<K, V>

Returns:

an entry with the least key, or null if this map is empty
firstEntry()

Redeclares as abstract: java.util.SequencedMap.firstEntry.

Returns a key-value mapping associated with the least key in this map, or null if the map is empty.

public Map.Entry<K, V>

Returns:

an entry with the greatest key less than or equal to key, or null if there is no such key
floorEntry(K
the key
key)

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.

public K

Returns:

the greatest key less than or equal to key, or null if there is no such key
floorKey(K
the key
key)

Returns the greatest key less than or equal to the given key, or null if there is no such key.

public NavigableMap<K, V>

Returns:

a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey
headMap(K
high endpoint of the keys in the returned map
toKey, boolean
true if the high endpoint is to be included in the returned view
inclusive)

Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) toKey.

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

Redeclares java.util.SortedMap.headMap.

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

public Map.Entry<K, V>

Returns:

an entry with the least key greater than key, or null if there is no such key
higherEntry(K
the key
key)

Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.

public K

Returns:

the least key greater than key, or null if there is no such key
higherKey(K
the key
key)

Returns the least key strictly greater than the given key, or null if there is no such key.

public Map.Entry<K, V>

Returns:

an entry with the greatest key, or null if this map is empty
lastEntry()

Redeclares as abstract: java.util.SequencedMap.lastEntry.

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

public Map.Entry<K, V>

Returns:

an entry with the greatest key less than key, or null if there is no such key
lowerEntry(K
the key
key)

Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.

public K

Returns:

the greatest key less than key, or null if there is no such key
lowerKey(K
the key
key)

Returns the greatest key strictly less than the given key, or null if there is no such key.

public Map.Entry<K, V>

Returns:

the removed first entry of this map, or null if this map is empty
pollFirstEntry()

Redeclares as abstract: java.util.SequencedMap.pollFirstEntry.

Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty (optional operation).

public Map.Entry<K, V>

Returns:

the removed last entry of this map, or null if this map is empty
pollLastEntry()

Redeclares as abstract: java.util.SequencedMap.pollLastEntry.

Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty (optional operation).

public default NavigableMap<K, V>

Returns:

a reverse-ordered view of this map, as a NavigableMap
reversed()

Overrides default java.util.SortedMap.reversed.

Returns a reverse-ordered view of this map.

public NavigableMap<K, V>

Returns:

a view of the portion of this map whose keys range from fromKey to toKey
subMap(K
low endpoint of the keys in the returned map
fromKey, boolean
true if the low endpoint is to be included in the returned view
fromInclusive, K
high endpoint of the keys in the returned map
toKey, boolean
true if the high endpoint is to be included in the returned view
toInclusive)

Returns a view of the portion of this map whose keys range from fromKey to toKey.

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

Redeclares java.util.SortedMap.subMap.

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

public NavigableMap<K, V>

Returns:

a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey
tailMap(K
low endpoint of the keys in the returned map
fromKey, boolean
true if the low endpoint is to be included in the returned view
inclusive)

Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) fromKey.

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

Redeclares java.util.SortedMap.tailMap.

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

Inherited from java.util.SortedMap:
comparatorentrySetfirstKeykeySetlastKeyputFirstputLastvalues

Method Detail

ceilingEntryback to summary
public Map.Entry<K, V> ceilingEntry(K key)

Returns a key-value mapping associated with the least key greater than or equal to the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:Map.Entry<K, V>

an entry with the least key greater than or equal to key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
ceilingKeyback to summary
public K ceilingKey(K key)

Returns the least key greater than or equal to the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:K

the least key greater than or equal to key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
descendingKeySetback to summary
public NavigableSet<K> descendingKeySet()

Returns a reverse order NavigableSet view of the keys contained in this map. The set's iterator returns the keys in descending 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:NavigableSet<K>

a reverse order navigable set view of the keys in this map

descendingMapback to summary
public NavigableMap<K, V> descendingMap()

Returns a reverse order view of the mappings contained in this map. The descending map is backed by this map, so changes to the map are reflected in the descending map, and vice-versa. If either map is modified while an iteration over a collection view of either map is in progress (except through the iterator's own remove operation), the results of the iteration are undefined.

The returned map has an ordering equivalent to Collections.reverseOrder(comparator()). The expression m.descendingMap().descendingMap() returns a view of m essentially equivalent to m.

Returns:NavigableMap<K, V>

a reverse order view of this map

firstEntryback to summary
public Map.Entry<K, V> firstEntry()

Redeclares as abstract: java.util.SequencedMap.firstEntry.

Returns a key-value mapping associated with the least key in this map, or null if the map is empty.

Returns:Map.Entry<K, V>

an entry with the least key, or null if this map is empty

floorEntryback to summary
public Map.Entry<K, V> floorEntry(K key)

Returns a key-value mapping associated with the greatest key less than or equal to the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:Map.Entry<K, V>

an entry with the greatest key less than or equal to key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
floorKeyback to summary
public K floorKey(K key)

Returns the greatest key less than or equal to the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:K

the greatest key less than or equal to key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
headMapback to summary
public NavigableMap<K, V> headMap(K toKey, boolean inclusive)

Returns a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) 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 of the keys in the returned map

inclusive:boolean

true if the high endpoint is to be included in the returned view

Returns:NavigableMap<K, V>

a view of the portion of this map whose keys are less than (or equal to, if inclusive is true) 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
headMapback to summary
public SortedMap<K, V> headMap(K toKey)

Redeclares java.util.SortedMap.headMap.

Doc from java.util.SortedMap.headMap.

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.

Equivalent to headMap(toKey, false).

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
higherEntryback to summary
public Map.Entry<K, V> higherEntry(K key)

Returns a key-value mapping associated with the least key strictly greater than the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:Map.Entry<K, V>

an entry with the least key greater than key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
higherKeyback to summary
public K higherKey(K key)

Returns the least key strictly greater than the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:K

the least key greater than key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
lastEntryback to summary
public Map.Entry<K, V> lastEntry()

Redeclares as abstract: java.util.SequencedMap.lastEntry.

Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty.

Returns:Map.Entry<K, V>

an entry with the greatest key, or null if this map is empty

lowerEntryback to summary
public Map.Entry<K, V> lowerEntry(K key)

Returns a key-value mapping associated with the greatest key strictly less than the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:Map.Entry<K, V>

an entry with the greatest key less than key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
lowerKeyback to summary
public K lowerKey(K key)

Returns the greatest key strictly less than the given key, or null if there is no such key.

Parameters
key:K

the key

Returns:K

the greatest key less than key, or null if there is no such key

Exceptions
ClassCastException:
if the specified key cannot be compared with the keys currently in the map
NullPointerException:
if the specified key is null and this map does not permit null keys
navigableKeySetback to summary
public NavigableSet<K> navigableKeySet()

Returns a NavigableSet 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:NavigableSet<K>

a navigable set view of the keys in this map

pollFirstEntryback to summary
public Map.Entry<K, V> pollFirstEntry()

Redeclares as abstract: java.util.SequencedMap.pollFirstEntry.

Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty (optional operation).

Returns:Map.Entry<K, V>

the removed first entry of this map, or null if this map is empty

Exceptions
UnsupportedOperationException:
if the pollFirstEntry operation is not supported by this map
pollLastEntryback to summary
public Map.Entry<K, V> pollLastEntry()

Redeclares as abstract: java.util.SequencedMap.pollLastEntry.

Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty (optional operation).

Returns:Map.Entry<K, V>

the removed last entry of this map, or null if this map is empty

Exceptions
UnsupportedOperationException:
if the pollLastEntry operation is not supported by this map
reversedback to summary
public default NavigableMap<K, V> reversed()

Overrides default java.util.SortedMap.reversed.

Doc from java.util.SortedMap.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.

This method is equivalent to descendingMap.

Implementation Specification

The implementation in this interface returns the result of calling the descendingMap method.

Returns:NavigableMap<K, V>

a reverse-ordered view of this map, as a NavigableMap

Since
21
subMapback to summary
public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive)

Returns a view of the portion of this map whose keys range from fromKey to toKey. If fromKey and toKey are equal, the returned map is empty unless fromInclusive and toInclusive are both true. 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 of its range, or to construct a submap either of whose endpoints lie outside its range.

Parameters
fromKey:K

low endpoint of the keys in the returned map

fromInclusive:boolean

true if the low endpoint is to be included in the returned view

toKey:K

high endpoint of the keys in the returned map

toInclusive:boolean

true if the high endpoint is to be included in the returned view

Returns:NavigableMap<K, V>

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

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

Redeclares java.util.SortedMap.subMap.

Doc from java.util.SortedMap.subMap.

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.

Equivalent to subMap(fromKey, true, toKey, false).

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
tailMapback to summary
public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)

Returns a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) 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 of the keys in the returned map

inclusive:boolean

true if the low endpoint is to be included in the returned view

Returns:NavigableMap<K, V>

a view of the portion of this map whose keys are greater than (or equal to, if inclusive is true) 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
tailMapback to summary
public SortedMap<K, V> tailMap(K fromKey)

Redeclares java.util.SortedMap.tailMap.

Doc from java.util.SortedMap.tailMap.

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.

Equivalent to tailMap(fromKey, true).

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