Map — putIfAbsent

The putIfAbsent method in the Map interface is a convenient way to insert a key-value pair into a map only if the key is not already associated with a value or is associated with null. This avoids overwriting existing values.

map.putIfAbsent(key, value)

• Parameters:
• key: the key for the value to be inserted.
• value: the value to associate with the key if no value is currently associated.
• Returns:
• The current value associated with the key if it exists.
• null if no value was associated and the new key-value pair was successfully inserted.

Example Usage

import java.util.HashMap;
import java.util.Map;

public class MapPutIfAbsentExample {
    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();

        // Adding a key-value pair
        map.put("key1", "value1");

        // Trying to add the same key with a different value
        map.putIfAbsent("key1", "newValue1");

        // Adding a new key
        map.putIfAbsent("key2", "value2");

        // Printing the map
        System.out.println(map);
    }
}

Output

{key1=value1, key2=value2}