Dart Basic- Lists

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Lists in Dart

The dart:core library provides the List class that enables the creation and manipulation of lists. Lists are a collection of objects, and they can be classified into two types:

  • Fixed Length List
  • Growable List.


Fixed Length List


A fixed-length list is a list whose length cannot be changed after initialization. The syntax for creating a fixed-length list is as follows:

Declaring a list

The syntax for declaring a fixed-length list is as given below:

List list_name = List(initial_size);

The above syntax creates a list of the specified size, and all the elements in the list are initialized to null. The list cannot grow or shrink at runtime. Any attempt to resize the list will result in an exception.

Initializing a list

The syntax for initializing a fixed-length list is as follows:

list_name[index] = value;

Example:

void main() {
    List lst = List(3);
    lst[0] = 12;
    lst[1] = 13;
    lst[2] = 11;
    print(lst);
}

Output:

[12, 13, 11]

Growable List

A growable list is a list whose length can change at runtime. The syntax for declaring and initializing a growable list is as follows:

Declaring a List


The syntax for declaring a growable list is as given below:

List list_name = [val1, val2, val3, …];

OR

List list_name = List();

The above syntax creates a list of size zero.

Initializing a List


The syntax for initializing a growable list is as given below:

list_name[index] = value;

Example:

void main() {
    List lst = [];
    lst.add(12);
    lst.add(13);
    lst.add(11);
    print(lst);
}

Output:

[12, 13, 11]

List Properties


The List class in Dart provides several properties for working with lists. Here are some of the commonly used properties:

List Properties

NoMethods & Description
1first
Returns the first element in the list.
2isEmpty
Returns true if the collection has no elements.
3isNotEmpty
Returns true if the collection has at least one element.
4length
Returns the size of the list.
5last
Returns the last element in the list.
6reversed
Returns an iterable object containing the lists values in the reverse order.
7Single
Checks if the list has only one element and returns it.

Example:

void main() {
  // create a list of numbers
  var numbers = [1, 2, 3, 4, 5];

  // access the first and last elements
  print(numbers.first); // prints 1
  print(numbers.last); // prints 5

  // check if the list is empty or not
  print(numbers.isEmpty); // prints false
  print(numbers.isNotEmpty); // prints true

  // get the length of the list
  print(numbers.length); // prints 5

  // get an iterable object containing the list's values in reverse order
  var reversedNumbers = numbers.reversed;
  print(reversedNumbers); // prints (5, 4, 3, 2, 1)

  // check if the list has only one element and return it
  print([6].single); // prints 6
}

Output:

1
5
false
true
5
(5, 4, 3, 2, 1)
6
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