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Insert elements to HashMap collection in java (example)

What is HashMap collection in java?

Class hierarchy of HashMap collection:

Fig 1: Class hierarchy of HashMap collection

Methods to insert or add elements to HashMap:

No.Method Name Description
1V put(K key, V value) Associates the specified value with the specified key in this map.
2void putAll(Map<? extends K,? extends V> m) Copies all of the mappings from the specified map to this map.
3default V putIfAbsent(K key, V value) If the specified key is not already associated with a value (or is mapped to null) associates it with the given value and returns null, else returns the current value.

Insert objects to HashMap collection (java /example)

package org.learn.collection.map.hmap;

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

public class DemoPutToHashMap {

	public static void main(String[] args) {
		Map<String, String> mapSportsPersonality = new HashMap<>();
		System.out.println("Demo of put methods of HashMap collection: ");
		demoPutMethod(mapSportsPersonality);
	}

	private static void demoPutMethod(Map<String, String> mapSportsPersonality) {
		System.out.println("1. Orignal HashMap:\n" + mapSportsPersonality);
		
		mapSportsPersonality.put("Tennis", "Federer");
		mapSportsPersonality.put("Cricket", "Bradman");
		System.out.println("2. Added Tennis &  Cricket using put: \n" + mapSportsPersonality);

		Map<String, String> newSportsMap = new HashMap<>();
		newSportsMap.put("Golf", "Woods");
		newSportsMap.put("Boxer", "Ali");

		mapSportsPersonality.putAll(newSportsMap);
		System.out.println("3. Added another map using putAll to map:\n" + mapSportsPersonality);

		mapSportsPersonality.putIfAbsent("Baseball", "Trout");

		// key Baseball already added to map, so "Kershaw" would not be added
		mapSportsPersonality.putIfAbsent("Baseball", "Kershaw");
		System.out.println("4. Added Baseball using putIfAbsent to map:\n" + mapSportsPersonality);
	}
}

Output: string objects to HashMap (java /example)

Demo of put methods of HashMap collection: 
1. Orignal HashMap:
{}
2. Added Tennis &  Cricket using put: 
{Tennis=Federer, Cricket=Bradman}
3. Added another map using putAll to map:
{Tennis=Federer, Cricket=Bradman, Golf=Woods, Boxer=Ali}
4. Added Baseball using putIfAbsent to map:
{Tennis=Federer, Cricket=Bradman, Golf=Woods, Baseball=Trout, Boxer=Ali}
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