Java HashMap keySet() Method
Example
Return all the keys in a map:
import java.util.HashMap;
public class Main {
public static void main(String[] args) {
HashMap<String, String> capitalCities = new HashMap<String, String>();
capitalCities.put("England", "London");
capitalCities.put("Germany", "Berlin");
capitalCities.put("Norway", "Oslo");
capitalCities.put("USA", "Washington DC");
System.out.println(capitalCities.keySet());
}
}
Definition and Usage
The keySet() method returns a set containing all of the keys in the map.
To learn about sets, see our Java HashSet tutorial.
Note: The returned set is a view of the map, which means that changing the set also changes the map.
Syntax
public Set<K> keySet()K refers to the data type of the keys of the map.
Technical Details
| Returns: | A set containing all of the keys in the map. |
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Related Pages
❮ HashMap Methods
