Summary - Collections

Combine List, Set and Map to write a phone book.

Summary - Collections

In this group we learned four core collections: List is ordered and allows duplicates; Set holds unique elements; Map stores key-value pairs; Queue works in FIFO order. Their common ancestor is Iterable.

Each collection fits its scenario. List for ordered data, Set for deduplication, Map for fast lookup, Queue for ordered processing. Iterable offers lazy traversal.

Now let's do an exercise that uses them together: create three different collections and print their lengths.

Exercise Create three collections

Create a List<int> (3 elements), a Set<int> (2 elements) and a Map<String, int> (2 pairs). Print the length of each on a separate line.

Show example solution

void main() {
  var list = <int>[1, 2, 3];
  var set = <int>{4, 5};
  var map = <String, int>{'a': 1, 'b': 2};
  print(list.length);
  print(set.length);
  print(map.length);
}

Test yourself

Match collections to their purpose

List

Ordered, duplicates
Set

Unique elements
Map

Key-value
Queue

FIFO order
Which collection stores key-value pairs?
- List
- Map
- Queue
- Iterable
Show answer

Map — Map stores key-value pairs.

Next lesson: map

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