Map keySet() Method in Java with Examples
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.
Syntax:
Set keySet()
Parameters: This method has no argument.
Returns: This method returns a set containing keys of the specified map.
Below programs show the implementation of int keySet() method.
Program 1:
// Java code to show the implementation of// isEmpty method in Map interfaceimport java.util.*;public class GfG { // Driver code public static void main(String[] args) { // Initializing a Map of type HashMap Map<String, String> map = new HashMap<>(); System.out.println(map); System.out.println(map.isEmpty()); }} |
Output:
{}
true
Program 2: Below is the code to show implementation of hashCode().
// Java code to show the implementation of// keySet method in Map interfaceimport java.util.*;public class GfG { // Driver code public static void main(String[] args) { // Initializing a Map of type HashMap Map<Integer, String> map = new HashMap<>(); Set<Integer> s = new HashSet<>(); map.put(1, "One"); map.put(3, "Three"); map.put(5, "Five"); map.put(7, "Seven"); map.put(9, "Nine"); System.out.println(map); s = map.keySet(); System.out.println(s); }} |
Output:
{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine}
[1, 3, 5, 7, 9]
Reference:
Oracle Docs
