how to instantiate hashmap in java

To instantiate a HashMap object in Java, you can use the following syntax:

HashMap<KeyType, ValueType> map = new HashMap<>();

Here, KeyType is the type of the keys in the map and ValueType is the type of the values in the map. You can specify any type for the keys and values as long as they are compatible with the HashMap class.

For example, to create a HashMap that maps strings to integers, you can use the following code:

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

You can also specify the initial capacity and load factor of the HashMap when instantiating it. For example:

HashMap<String, Integer> map = new HashMap<>(16, 0.75f);

Here, the initial capacity is set to 16 and the load factor is set to 0.75.

You can then add key-value pairs to the map using the put method:

map.put("key1", 1);
map.put("key2", 2);
map.put("key3", 3);

You can retrieve the value for a given key using the get method:

int value = map.get("key1");

You can also use the containsKey method to check if a key is present in the map:

if (map.containsKey("key1")) {
    // Key is present in the map
} else {
    // Key is not present in the map
}