**Course Title:** Mastering Dart: From Fundamentals to Flutter Development **Section Title:** Working with Collections and Generics **Topic:** Dart collections: lists, sets, and maps In this topic, we'll delve into Dart collections, exploring lists, sets, and maps in-depth. Dart collections are essential data structures that enable you to store and manipulate multiple values in a single variable. ### Lists Lists are ordered collections of elements, allowing you to store and access elements by their index. In Dart, lists are implemented as a growable array, meaning they can be dynamically resized as elements are added or removed. Here's an example of creating and using a list in Dart: ```dart void main() { // Create a new list List<String> colors = ['red', 'green', 'blue']; // Access elements by index print(colors[0]); // Output: red // Add elements to the end of the list colors.add('yellow'); print(colors); // Output: [red, green, blue, yellow] // Remove elements from the list colors.remove('green'); print(colors); // Output: [red, blue, yellow] // Use the spread operator to create a new list from another list List<String> newColors = [...colors]; print(newColors); // Output: [red, blue, yellow] } ``` Some key methods for working with lists in Dart include: * `add(element)`: Adds the specified element to the end of the list. * `remove(element)`: Removes the first occurrence of the specified element in the list. * `removeAt(index)`: Removes the element at the specified index. * `length`: Returns the number of elements in the list. ### Sets Sets are unordered collections of unique elements. Sets are useful for quickly checking whether an element is present or not. In Dart, sets are implemented as a hash table. Here's an example of creating and using a set in Dart: ```dart void main() { // Create a new set Set<String> uniqueColors = {'red', 'green', 'blue'}; // Check if an element is in the set print(uniqueColors.contains('red')); // Output: true // Add an element to the set uniqueColors.add('yellow'); print(uniqueColors); // Output: {red, green, blue, yellow} // Remove an element from the set uniqueColors.remove('green'); print(uniqueColors); // Output: {red, blue, yellow} // Use the spread operator to create a new set from another set Set<String> newUniqueColors = {...uniqueColors}; print(newUniqueColors); // Output: {red, blue, yellow} } ``` Some key methods for working with sets in Dart include: * `add(element)`: Adds the specified element to the set. * `remove(element)`: Removes the specified element from the set. * `contains(element)`: Returns whether the specified element is in the set. * `length`: Returns the number of elements in the set. ### Maps Maps are collections of key-value pairs. You can access and manipulate values in a map by their corresponding key. In Dart, maps are implemented as a hash table. Here's an example of creating and using a map in Dart: ```dart void main() { // Create a new map Map<String, int> personAges = { 'John': 25, 'Jane': 30, 'Bob': 35 }; // Access values by key print(personAges['John']); // Output: 25 // Add key-value pairs to the map personAges['Alice'] = 20; print(personAges); // Output: {John: 25, Jane: 30, Bob: 35, Alice: 20} // Remove key-value pairs from the map personAges.remove('Bob'); print(personAges); // Output: {John: 25, Jane: 30, Alice: 20} // Update values by key personAges['Jane'] = 31; print(personAges); // Output: {John: 25, Jane: 31, Alice: 20} } ``` Some key methods for working with maps in Dart include: * `put(key, value)`: Adds the specified key-value pair to the map. * `remove(key)`: Removes the specified key-value pair from the map. * `containsKey(key)`: Returns whether the specified key is in the map. * `length`: Returns the number of key-value pairs in the map. ### Conclusion Dart collections provide efficient and flexible data structures for storing and manipulating multiple values. By mastering Dart collections, you can write more effective and efficient code. In the next topic, we'll explore how to use generics for type-safe collections. **What's next?** In the next topic, we'll cover "Using generics for type-safe collections." You'll learn how to ensure type safety in your collections and prevent errors at runtime. **External Resources** For more information on Dart collections, refer to the [Dart documentation](https://dart.dev/guides/libraries/library-tour#maps-and-sets). **Leave a comment/ask for help** If you have any questions or need help with Dart collections, feel free to leave a comment. We'll respond with detailed answers and explanations.