Java HashMap putIfAbsent() Method
Example
Add entries into 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");
// Add new entries only if they don't exist
capitalCities.putIfAbsent("Canada", "Ottawa");
capitalCities.putIfAbsent("England", "Cambridge");
System.out.println(capitalCities);
}
}
Definition and Usage
The putIfAbsent() method writes an entry into the map. If an entry with the same key already exists and its value is not null then the map is not changed.
Syntax
public V putIfAbsent(K key, V value)K and V refer to the data types of the keys and values of the map.
Parameter Values
| Parameter | Description |
|---|---|
| key | Required. The key of the map entry. |
| value | Required. The value of the map entry. |
Technical Details
| Returns: | If an entry exists with the specified key then it returns the value of that entry, otherwise it returns null. |
|---|
Related Pages
❮ HashMap Methods
