Basic operations on maps

Map is quite different from the other collections. Let’s learn how to perform the basic operations on Map.

Adding elements to a map

There is no add() method for Map. We can add elements to a Map interface using the put() method:

Map<String, Integer> gfNrMap = new HashMap<>();gfNrMap.put("Ross", 12);
gfNrMap.put("Chandler", 8);

This adds two key-value pairs to Map. Let’s see how we can get the values out again.

Getting elements from a map

We can get elements from a Map interface using the get() method. This is how we can get the Integer value associated with the Ross key:

int rossNrOfGfs = gfNrMap.get("Ross");

We can also use the key to modify the values of the map.

Changing the elements of a map

We can change the elements in a Map interface using the put() method with an existing key:

gfNrMap.put("Chandler", 9);

The preceding code changes the value of 8 to 9...