Hashtable merge(K, V, BiFunction) in Java

merge(K, V, BiFunction): This method is available in java.util.Hashtable class of Java.

Syntax:

V java.util.Hashtable.merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction)

This method takes three arguments. If the specified key is not already associated with a value or is associated with null, associate it with the given non-null value. Otherwise, replaces the associated value with the results of the given remapping function, or removes it if the result is null.

Parameters: Three parameters are required for this method.

key: key with which the resulting value is to be associated.

value: the non-null value to be merged with the existing value associated with the key or if no existing value or a null value is associated with the key, to be associated with the key.

remappingFunction: the remapping function to recompute a value if present.

Returns: the new value associated with the specified key, or null if no value is associated with the key.

Throws:

ConcurrentModificationException - if it is detected that the remapping function modified this map

Approach

Java

import java.util.Hashtable;
import java.util.function.BiFunction;

public class Hashtablemerge {
    public static void main(String[] args) {
        Hashtable<String, Integer> hashtable =
                new Hashtable<String, Integer>();

        hashtable.put("Hello", 1);
        hashtable.put("World", 2);

        String key = "Java";
        Integer value = 5;
        BiFunction<? super Integer, ? super Integer, 
          ? extends Integer> remappingFunction = 
                                  (a, b) -> a + b;
        hashtable.merge(key, value, remappingFunction);
        System.out.println(hashtable);

    }
}

Output:

{Java=5, World=2, Hello=1}