Map keySet() Method in Java with Examples
Last Updated :
27 Nov, 2024
Improve
This method is used to return a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa.
Example:
// Java Program Implementing Map
// keySet() Method
import java.util.*;
public class GfG
{
public static void main(String[] args)
{
// Initializing a Map of type HashMap
Map<String, String> m = new HashMap<>();
// Adding Elements in Map
m.put("1" , "One");
m.put("2" , "Two");
// Printing Key Sets
System.out.println(m.keySet());
}
}
Output
[1, 2]
Syntax of Method
Set keySet()
Parameters: This method has no argument.
Returns: This method returns a set containing keys of the specified map.
Example for Map keySet()
Below is the code to show implementation of hashCode():
// Java code to show the implementation of
// keySet method in Map interface
import java.util.*;
public class GfG
{
public static void main(String[] args)
{
// Initializing a Map of type HashMap
Map<Integer, String> m = new HashMap<>();
Set<Integer> s = new HashSet<>();
// Adding elements of HashMap
m.put(1, "One");
m.put(3, "Three");
m.put(5, "Five");
m.put(7, "Seven");
m.put(9, "Nine");
System.out.println(m);
// Storing keys in Set
s = m.keySet();
System.out.println(s);
}
}
Output:
{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine}
[1, 3, 5, 7, 9]
Reference: Oracle Docs
