Return Value of put() in HashMap

package com.payu.Payu;

import java.util.*;

public class HashMap_Example {
    public static void main(String[] args) {

        // Creating an empty HashMap
        HashMap<Integer, String> hashmap = new HashMap<Integer, String>();

        // Mapping string values to int keys
        hashmap.put(10, "HashMap");
        hashmap.put(15, "4");
        hashmap.put(25, "You");

        // Displaying the HashMap
        System.out.println("Initial Mappings are: " + hashmap);

        // Inserting existing key along with new value
        // return type of put is type of values i.e. String and containing the old value 
        String returned_value = hashmap.put(10, "abc");

        // Verifying the returned value
        System.out.println("Returned value is: " + returned_value);

        // Inserting new key along with new value
        // return type of put is type of values i.e. String ; since it is new key ,return value will be null

        returned_value = hashmap.put(20, "abc");

        // Verifying the returned value
        System.out.println("Returned value is: " + returned_value);

        // Displayin the new map
        System.out.println("New map is: " + hashmap);
    }
}

Output :-

Initial Mappings are: {25=You, 10=HashMap, 15=4}
Returned value is: HashMap
Returned value is: null
New map is: {20=abc, 25=You, 10=abc, 15=4}

The method put has a return type same with the value:

    @Override
    public V put(K key, V value) {
        return putImpl(key, value);
    }

The method associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

It returns the previous value associated with key, or null if there was no mapping for key.So, your points are right.

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