Java : Collection Framework : HashMap (Put Return)

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HashMapExample.java

import java.util.HashMap;

/*
 * Example of put(K key,V value) method.
 */
public class HashMapExample
{
    public static void main( String[] args )
    {

        HashMap<Integer, String> hashMap = new HashMap<Integer, String>();

        /*
         * 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.
         * 
         * Returns: the previous value associated with key, or null if there was
         * no mapping for key. (A null return can also indicate that the map
         * previously associated null with key.)
         */
        String value = hashMap.put(1, "Apple");

        System.out.println("Previous value associated with key '1' : " + value);
        System.out.println("hashMap : " + hashMap + "\n");

        value = hashMap.put(1, "Ball");

        System.out.println("Previous value associated with key '1' : " + value);
        System.out.println("hashMap : " + hashMap);

    }
}

Output

Previous value associated with key '1' : null
hashMap : {1=Apple}

Previous value associated with key '1' : Apple
hashMap : {1=Ball}

To Download HashMapDemoPutReturnValue  Project Click the below link
https://sites.google.com/site/javaee4321/java-collections/HashMapDemoPutReturnValue.zip?attredirects=0&d=1

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