Is it possible to use primitive data types as keys in data structures or databases?

Yes, in Java, primitive data types (int, long, char, boolean, etc.) cannot be used directly as keys in data structures like HashMap because they are not objects. However, Java provides wrapper classes for primitive types (Integer, Long, Character, Boolean, etc.), which can be used as keys.

For example:

import java.util.HashMap;

HashMap<Integer, String> map = new HashMap<>();
map.put(1, "one");
map.put(2, "two");

System.out.println(map.get(1)); // outputs: one

Here, the keys are Integer objects, not primitive ints. Autoboxing in Java automatically converts primitives to wrapper objects.