Is it possible to have multiple elements with the same key in a HashMap collection?

In a HashMap collection in Java, keys are unique. If you try to add an element with a key that already exists in the map, the old value will be overwritten with the new one. Thus, there cannot be multiple elements with the same key in a HashMap.

Example:

Map<String, Integer> map = new HashMap<>();
map.put("key1", 1);
map.put("key1", 2); // the value for "key1" will be replaced with 2
System.out.println(map.get("key1")); // will output 2