SortedMap Interface in Java

Last Updated: 06 March, 2023

SortedMap is an interface in the Java collection framework. SortedMap was introduced in the JDK 1.2 version and is available in the java.util package.

SortedMap extends the Map interface and stores the elements in the form of key-value pairs. SortedMap ensures that the entries are maintained in ascending key order.

The java.util.TreeMap class implements SortedMap interface in Java.

Java SortedMap declaration:

public interface SortedMap<K,V> extends Map<K,V>

Here, K is the key Object type and V is the value Object type.

Java SortedMap Methods

Java SortedMap example - Add, Update and Remove elements

import java.util.SortedMap; import java.util.TreeMap; public class SortedMapExample { public static void main(String args[]) { SortedMap<Integer, String> countries = new TreeMap<>(); // Adding key-value into the map countries.put(91, "India"); countries.put(81, "Japan"); countries.put(49, "Germany"); countries.put(65, "Singapore"); countries.put(31, "Netherlands"); // Printing map elements System.out.println("SortedMap Elements: " + countries); // Removes the mapping for a key from this map if it is present System.out.println("\nThe value associated with the key: " + countries.remove(49)); System.out.println("\nSortedMap Elements after Remove:\n" + countries + "\n"); // Updating value using put() method countries.put(81, "Japan-JP"); System.out.println("SortedMap Elements after updating using put() method:\n" + countries); // Updating value using replace() method countries.replace(65, "Singapore-SG"); System.out.println("\nSortedMap Elements after updating using replace() method:\n" + countries); // If the specified key is not already associated with a value countries.putIfAbsent(54, "Argentina"); System.out.println("\nSortedMap Elements after adding new key/value: "); System.out.println(countries); SortedMap<Integer, String> otherCountries = new TreeMap<>(); otherCountries.put(973, "Bahrain"); otherCountries.put(358, "Finland"); otherCountries.put(263, "Zimbabwe"); // Copies all of the mappings from the specified map to this map countries.putAll(otherCountries); System.out.println("\nSortedMap Elements after adding new map:"); System.out.println(countries); } }

Output

SortedMap Elements:{31=Netherlands, 49=Germany, 65=Singapore, 81=Japan, 91=India}

The value associated with the key: Germany

SortedMap Elements after Remove:
{31=Netherlands, 65=Singapore, 81=Japan, 91=India}

SortedMap Elements after updating using put() method:
{31=Netherlands, 65=Singapore, 81=Japan-JP, 91=India}

SortedMap Elements after updating using replace() method:
{31=Netherlands, 65=Singapore-SG, 81=Japan-JP, 91=India}

SortedMap Elements after adding new key/value:
{31=Netherlands, 54=Argentina, 65=Singapore-SG, 81=Japan-JP, 91=India}

SortedMap Elements after adding new map:
{31=Netherlands, 54=Argentina, 65=Singapore-SG, 81=Japan-JP, 91=India, 263=Zimbabwe, 358=Finland, 973=Bahrain}

Java SortedMap example with utility methods

import java.util.SortedMap; import java.util.TreeMap; public class SortedMapExample2 { public static void main(String args[]) { SortedMap<Integer, String> countries = new TreeMap<>(); // Adding key-value into the map countries.put(91, "India"); countries.put(81, "Japan"); countries.put(49, "Germany"); countries.put(65, "Singapore"); countries.put(31, "Netherlands"); // Printing map elements System.out.println("SortedMap Elements: " + countries); System.out.println("Size of map: " + countries.size()); // Returns the value to which the specified key is mapped System.out.println("Value of specified key (49): " + countries.get(49)); // Returns true if this map contains no key-value mappings else false System.out.println("Is map is empty: " + countries.isEmpty()); // Returns the first (lowest) key currently in this map. System.out.println("first (lowest) key: " + countries.firstKey()); // Returns the last (highest) key currently in this map. System.out.println("Last (highest) key: " + countries.lastKey()); // Returns a Set view of the keys contained in this map System.out.println("Keys contained in this map: " + countries.keySet()); // Returns a Collection view of the values contained in this map System.out.println("Values contained in this map: " + countries.values()); // Returns a view of the portion of this map whose keys range from fromKey, // inclusive, to toKey, exclusive. SortedMap<Integer, String> subMap = countries.subMap(49, 81); System.out.println("Sub Map elements: " + subMap); // Removes all of the mappings from this map countries.clear(); // Printing map elements after calling clear() method System.out.println("SortedMap Elements: " + countries); } }

Output

SortedMap Elements: {31=Netherlands, 49=Germany, 65=Singapore, 81=Japan, 91=India}
Size of map: 5
Value of specified key (49): Germany
Is map is empty: false
first (lowest) key: 31
Last (highest) key: 91
Keys contained in this map: [31, 49, 65, 81, 91]
Values contained in this map: [Netherlands, Germany, Singapore, Japan, India]
Sub Map elements: {49=Germany, 65=Singapore}
SortedMap Elements: {}

Reference: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/SortedMap.html