Java TreeMap

In this tutorial, we will learn about the Java TreeMap class and its operations with the help of examples.

The TreeMap class of the Java collections framework provides the tree data structure implementation.

The TreeMap in Java is used to implement Map interface and NavigableMap along with the Abstract Class. The map 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. This proves to be an efficient way of sorting and storing the key-value pairs. The storing order maintained by the treemap must be consistent with equals just like any other sorted map, irrespective of the explicit comparators. Let’s see how to create a map object using this class.

Example:

/// Java Program to illustrate the Treemap Class 
import java.util.*; 

public class Codemistic { 

	public static void main(String[] args) 
	{ 
		Map<String, Integer> map = new TreeMap<>(); 

		map.put("ayush", 10); 
		map.put("anvi", 30); 
		map.put("pragya", 20); 

		for (Map.Entry<String, Integer> e : map.entrySet()) 
			System.out.println(e.getKey() + " "
							+ e.getValue()); 
	} 
} 
output:
ayush 20
anvi 10
pragya 30

Important Features of a TreeMap:

• This class is a member of Java Collections Framework.
• The class implements Map interfaces including NavigableMap, SortedMap and extends AbstractMap class.
• TreeMap in Java does not allow null keys (like Map) and thus a NullPointerException is thrown. However, multiple null values can be associated with different keys.
• Entry pairs returned by the methods in this class and its views represent snapshots of mappings at the time they were produced. They do not support the Entry.setValue method.

Methods in Java TreeMap