LinkedHashMap computeIfAbsent(K, Function) in Java

computeIfAbsent(K, Function): This method is available in java.util.LinkedHashMap class of Java.

Syntax:

V java.util.HashMap.computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction)

This method takes two arguments. If the specified key is not already associated with a value attempts to compute its value using the given mapping function and enters it into this map unless null.

Parameters: Two parameters are require for this method.

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

mappingFunction: the mapping function to compute a value.

Returns: the current (existing or computed) value associated with the specified key, or null if the computed value is null.

Throws:

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

Approach

Java

import java.util.LinkedHashMap;
import java.util.function.Function;

public class LinkedHashMapcomputeIfAbsent {

    public static void main(String args[]) {

        LinkedHashMap<String, Integer> linkedHashMap = 
                     new LinkedHashMap<String, Integer>();

        linkedHashMap.put("Java", 1);
        linkedHashMap.put("1", 2);

        String key = "1";
        Function<? super String, ? extends Integer> 
          mappingFunction = a -> Integer.parseInt(a);

        linkedHashMap.computeIfAbsent(key, mappingFunction);

        System.out.println(linkedHashMap);
    }

}

Output:

{Java=1, 1=2}