The put() method allows you to add key-value pairs to the HashMap. New AbstractMap.SimpleEntry("city", "budapest"))) 6. One of the simplest ways to initialize a HashMap is to use the put() method. Now if we need a mutable or growing map after initialization, we can create any of the implementations of the Map interface and pass these immutable maps in the constructor: Map map = new HashMap ( 1 Answer Sorted by: 12 Less typing, Map is the Interface (same with List) for that class so its easier to pass a Map around than a HashMap since the functionality is the same the only difference is the implementation. Note that the factory methods produce immutable maps, hence any mutation will result in a UnsupportedOperationException.Īlso, they do not allow null keys or duplicate keys. In between these angle brackets, you tell Java what sort of values. New AbstractMap.SimpleEntry("zip", "000000"), import // Note the HashMaps key is a String and value is an Integer HashMap hm new HashMap(). After declaring that you want to set up a HashMap, you need a pair of angle brackets (<>).New AbstractMap.SimpleEntry("city", "budapest"), New AbstractMap.SimpleEntry("name", "John"), Hashmap () It is the default constructor that creates an instance of a hashmap with the initial capacity of 16 and load factor 0.75. It's similar to the Map.of() but has no limitations on the number of key-value pairs: Map map = Map.ofEntries(
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