NavigableMap Interface in Java
Last Updated :
23 Jul, 2025
The NavigableMap interface is a member of the Java Collection Framework. It belongs to java.util package and It is an extension of SortedMap which provides convenient navigation methods for dealing with elements that are sorted based on their keys. This interface allows us to navigate through the map's keys in a more efficient and flexible manner, providing methods for finding entries based on certain key ranges, such as greater than, less than, or equal to a particular key.
- In NavigableMap entries are automatically sorted by their keys, allowing easy navigation in both forward and reverse order.
- We can query keys within specific ranges, making it useful for operations that require finding values within limits.
- Methods like lowerLey(), higherEntry(), floorEntry(), and ceilingEntry() let us quickly find entries around the key.
- Create submaps from a range of keys using methods like subMap(), gheadMap() and tailMap()
Example: This example demonstrates how to add elements to a NavigableMap and print its content using TreeMap.
Java
// Java program to demonstrate
// working of NavigableMap
import java.util.*;
public class Geeks {
public static void main(String[] args) {
// Creating a NavigableMap using TreeMap
NavigableMap<Integer, String> m = new TreeMap<>();
// Adding elements to the map
m.put(1, "One");
m.put(3, "Three");
m.put(2, "Two");
System.out.println("NavigableMap: " + m);
}
}
OutputNavigableMap: {1=One, 2=Two, 3=Three}
NavigableMap Hierarchy
NavigableMap implements Map<K,V>, SortedMap<K,V> interfaces. ConcurrentNavigableMap<K,V> extends NavigableMap. ConcurrentSkipListMap and TreeMap implements NavigableMap.
Example: This example demonstrates the use of various NavigableMap methods like put(), descendingKeySet(), floorEntry() to manipulate and access elements in a TreeMap.
Java
// Java program to demonstrate
// various methods of NavigableMap interface
import java.util.NavigableMap;
import java.util.TreeMap;
public class Geeks{
public static void main(String[] args)
{
// Instantiate an object
// Since NavigableMap
// is an interface so we
// use TreeMap
NavigableMap<String, Integer> nm
= new TreeMap<String, Integer>();
// Add elements using put() method
nm.put("C", 888);
nm.put("Y", 999);
nm.put("A", 444);
nm.put("T", 555);
nm.put("B", 666);
nm.put("A", 555);
// Print the contents on the console
System.out.println("Mappings of NavigableMap : "
+ nm);
System.out.printf("Descending Set : %s%n",
nm.descendingKeySet());
System.out.printf("Floor Entry : %s%n",
nm.floorEntry("L"));
System.out.printf("First Entry : %s%n",
nm.firstEntry());
System.out.printf("Last Key : %s%n", nm.lastKey());
System.out.printf("First Key : %s%n",
nm.firstKey());
System.out.printf("Original Map : %s%n", nm);
System.out.printf("Reverse Map : %s%n",
nm.descendingMap());
}
}
Output:
Declaration of NavigableMap Interface
In Java, the declaration of NavigableMap Interface can be done as:
NavigableMap<KeyType, ValueType> mapName;
Implementing Classes
The NavigableMap has two implementing classes which are ConcurrentSkipListMap and TreeMap. TreeMap is a Red-Black tree based NavigableMap implementation and it is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used. The TreeMap has the expected time cost of log(n) for insertion, deletion, and access operations. TreeMap is not synchronized and it has to be done externally.
Syntax:
NavigableMap<K, V> map = new TreeMap<K, V>();
Performing Various Operations on NavigableMap Interface
1. Adding Elements: To add elements to a NavigableMap we can use any methods of the Map interface.
Example: This example demonstrates adding elements to a NavigableMap and printing the sorted map.
Java
// Java program for adding elements
// to a NavigableMap
import java.util.*;
class Geeks {
public static void main(String args[])
{
// Instantiate an object
// Since NavigableMap is an interface
// We use TreeMap
NavigableMap<Integer, String> map
= new TreeMap<Integer, String>();
// Add elements using put()
map.put(3, "Geeks");
map.put(2, "For");
map.put(1, "Geeks");
System.out.println("NavigableMap: " + map);
}
}
OutputNavigableMap: {1=Geeks, 2=For, 3=Geeks}
2. Removing Elements: We can use the remove() method to remove elements from the NavigableMap. If we want to remove all the elements from the map we can use clear() method.
Example: This example demonstrates removing elements from a NavigableMap using remove() and clearing the entire map using the clear() method.
Java
// Java Program to demonstrates the
// working of remove() and clear()
import java.util.*;
class Geeks {
public static void main(String args[])
{
// Instantiate an object
// Since NavigableMap
// is an interface
// We use TreeMap
NavigableMap<Integer, String> map
= new TreeMap<Integer, String>();
// Add elements using put()
map.put(3, "Java");
map.put(2, "C++");
map.put(1, "Python");
map.put(4, "Js");
// Print the contents on the console
System.out.println("NavigableMap: " + map);
// Remove elements using remove()
map.remove(4);
// Print the contents on the console
System.out.println(
"NavigableMap, after remove operation: "
+ map);
// Clear the entire map using clear()
map.clear();
System.out.println(
"NavigableMap, after clear operation: "
+ map);
}
}
OutputNavigableMap: {1=Python, 2=C++, 3=Java, 4=Js}
NavigableMap, after remove operation: {1=Python, 2=C++, 3=Java}
NavigableMap, after clear operation: {}
3. Accessing Elements: We can access the elements of a NavigableMap using get() method.
Example: This example demonstrates accessing elements in a NavigableMap using get() and displaying the set of keys using keySet() method.
Java
// Java Program to demosntrates
// how to access elemets in NavigableMap
import java.util.*;
public class Geeks {
public static void main(String[] args)
{
// Instantiate an object
// Since NavigableMap is an interface
// We use TreeMap
NavigableMap<Integer, String> map
= new TreeMap<Integer, String>();
// Add elements using put()
map.put(3, "Third");
map.put(2, "Second");
map.put(1, "First");
map.put(4, "Fourth");
// Accessing the elements using get()
// with key as a parameter
System.out.println(map.get(1));
System.out.println(map.get(3));
System.out.println("NavigableMap: " + map.keySet());
}
}
OutputFirst
Third
NavigableMap: [1, 2, 3, 4]
4. Iterating Elements: We can use the Iterator interface to traverse a NavigableMap. To handle the key-value pairs, we use Map.Entry<?> and the next() method to access element. Alternatively, we can use a for-each loop to get keys and fetch values using getValue() method.
Example: This example demonstrates traversing a NavigableMap using both an Iterator and a for-each loop to access keys and values.
Java
// Java Program to traverse a NavigableMap
import java.util.*;
class Geeks{
public static void main(String args[])
{
// Instantiate an object
// Since NavigableMap is an interface
// We use TreeMap
NavigableMap<Integer, String> map
= new TreeMap<Integer, String>();
// Add elements using put()
map.put(3, "Geeks");
map.put(2, "For");
map.put(1, "Geeks");
// Create an Iterator over the
// NavigableMap
Iterator<NavigableMap.Entry<Integer, String> > itr
= map.entrySet().iterator();
System.out.println("Traversing using Iterator: ");
// The hasNext() method is used to check if there is
// a next element The next() method is used to
// retrieve the next element
while (itr.hasNext()) {
NavigableMap.Entry<Integer, String> entry
= itr.next();
System.out.println("Key = " + entry.getKey()
+ ", Value = "
+ entry.getValue());
}
System.out.println("Traversing using for-each: ");
// Iterate using for-each loop
for (Map.Entry mapElement : map.entrySet()) {
// get the key using getKey()
int key = (int)mapElement.getKey();
// Finding the value
String value = (String)mapElement.getValue();
System.out.println("Key = " + key
+ ", Value = " + value);
}
}
}
OutputTraversing using Iterator:
Key = 1, Value = Geeks
Key = 2, Value = For
Key = 3, Value = Geeks
Traversing using for-each:
Key = 1, Value = Geeks
Key = 2, Value = For
Key = 3, Value = Geeks
Methods
NavigableMap inherits methods from the Map interface, SortedMap interface. The basic methods for adding elements, removing elements, and traversal are given by the parent interfaces. The methods of the NavigableMap are given in the following table. Here,
- K: The type of the keys in the map.
- V: The type of values mapped in the map.
Method | Description |
---|
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. |
ceilingKey(K key) | Returns the least key greater than or equal to the given key, or null if there is no such key. |
descendingKeySet() | Returns a reverse order NavigableSet view of the keys contained in this map. |
descendingMap() | Returns a reverse order view of the mappings contained in this map. |
firstEntry() | Returns a key-value mapping associated with the least key in this map, or null if the map is empty. |
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. |
floorKey(K key) | Returns the greatest key less than or equal to the given key, or null if there is no such key. |
headMap(K toKey) | Returns a view of the portion of this map whose keys are strictly less than toKey. |
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. |
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. |
higherKey(K key) | Returns the least key strictly greater than the given key, or null if there is no such key. |
lastEntry() | Returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. |
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. |
lowerKey(K key) | Returns the greatest key strictly less than the given key, or null if there is no such key. |
navigableKeySet() | Returns a NavigableSet view of the keys contained in this map. |
pollFirstEntry() | Removes and returns a key-value mapping associated with the least key in this map, or null if the map is empty. |
pollLastEntry() | Removes and returns a key-value mapping associated with the greatest key in this map, or null if the map is empty. |
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. |
subMap(K fromKey, K toKey) | Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. |
tailMap(K fromKey) | Returns a view of the portion of this map whose keys are greater than or equal to fromKey. |
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. |
Methods Inherited from Interface java.util.SortedMap
Method | DESCRIPTION |
---|
comparator() | Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys. |
entrySet() | Returns a Set view of the mappings contained in this map. |
firstKey() | Returns the first (lowest) key currently in this map. |
keySet() | Returns a Set view of the keys contained in this map. |
lastKey() | Returns the last (highest) key currently in this map. |
values() | Returns a Collection view of the values contained in this map. |
Methods Inherited from Interface java.util.Map
Method | Description |
---|
clear() | Removes all of the mappings from this map (optional operation). |
compute(K key, BiFunction<? super K,? super V,? extends V> remappingFunction) | Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). |
computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction) | If the specified key is not already associated with a value (or is mapped to null), attempts to compute its value using the given mapping function and enters it into this map unless null. |
computeIfPresent(K key, BiFunction<? super K,? super V,? extends V> remappingFunction) | If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value. |
containsKey(Object key) | Returns true if this map contains a mapping for the specified key. |
containsValue(Object value) | Returns true if this map maps one or more keys to the specified value. |
equals(Object o) | Compares the specified object with this map for equality. |
forEach(BiConsumer<? super K,? super V> action) | Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. |
get(Object key) | Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key. |
getOrDefault(Object key, V defaultValue) | Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key. |
hashCode() | Returns the hash code value for this map. |
isEmpty() | Returns true if this map contains no key-value mappings. |
merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction) | If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. |
put(K key, V value) | Associates the specified value with the specified key in this map (optional operation). |
putAll(Map<? extends K,? extends V> m) | Copies all of the mappings from the specified map to this map (optional operation). |
putIfAbsent(K key, V value) | If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value. |
remove(Object key) | Removes the mapping for a key from this map if it is present (optional operation). |
remove(Object key, Object value) | Removes the entry for the specified key only if it is currently mapped to the specified value. |
replace(K key, V value) | Replaces the entry for the specified key only if it is currently mapped to some value. |
replace(K key, V oldValue, V newValue) | Replaces the entry for the specified key only if currently mapped to the specified value. |
replaceAll(BiFunction<? super K,? super V,? extends V> function) | Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception. |
size() | Returns the number of key-value mappings in this map. |
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