TreeMap keySet() Method in Java with Examples

In Java, keySet() method of TreeMap class is present inside java.util package in Java is used to create a set out of the key elements contained in the treemap. It basically returns a set view of the keys or we can create a new set and store the key elements in them in ascending order. Since the set is backed by the map, any changes made to the map are reflected in the set, and vice-versa.

--> java.util Package
 --> TreeMap Class
 --> keySet() Method 

Syntax: 

tree_map.keySet()

Return Type: A set having the keys of the treemap in ascending order.

Example 1: Mapping String Values to Integer Keys. 

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
The set is: [10, 15, 20, 25, 30]

Example 2: Mapping Integer Values to String Keys

Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
The set is: [4, Geeks, Welcomes, You]

Note: Similarly the same operation can be performed with any type of Mappings with variation and combination of different data types.