In which cases should you use a HashMap data structure?

HashMap is a data structure that implements an associative array (dictionary), where keys are mapped to values using a hash function.

Use HashMap when:

• You need fast addition, removal, and lookup of elements by key (average O(1)).
• The order of elements does not matter, as HashMap does not guarantee order.
• Keys are unique and implement correct hashCode() and equals() methods.

Example in Python using a dictionary (analogous to HashMap):

# Creating a dictionary
my_map = {}

# Adding elements
my_map['apple'] = 5
my_map['banana'] = 3

# Lookup by key
print(my_map.get('apple'))  # Outputs 5

# Removing an element
my_map.pop('banana')

Thus, HashMap (or dictionary in Python) is convenient for quick data access by key.