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A very commonly used collection in programming is an array. Dart represents arrays in the form of List objects. A List is simply an ordered group of objects. The dart:core library provides the List class that enables creation and manipulation of lists.
The logical representation of a list in Dart is given below −
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test_list − is the identifier that references the collection.
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The list contains in it the values 12, 13, and 14. The memory blocks holding these values are known as elements.
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Each element in the List is identified by a unique number called the index. The index starts from zero and extends up to n-1 where n is the total number of elements in the List. The index is also referred to as the subscript.
Lists can be classified as −
- Fixed Length List
- Growable List
Let us now discuss these two types of lists in detail.
Fixed Length List
A fixed length list’s length cannot change at runtime. The syntax for creating a fixed length list is as given below −
Step 1 − Declaring a list
The syntax for declaring a fixed length list is given below −
var list_name = new List(initial_size)
The above syntax creates a list of the specified size. The list cannot grow or shrink at runtime. Any attempt to resize the list will result in an exception.
Step 2 − Initializing a list
The syntax for initializing a list is as given below −
lst_name[index] = value;
Example
void main() { var lst = new List(3); lst[0] = 12; lst[1] = 13; lst[2] = 11; print(lst); }
It will produce the following output −
[12, 13, 11]
Growable List
A growable list’s length can change at run-time. The syntax for declaring and initializing a growable list is as given below −
Step 1 − Declaring a List
var list_name = [val1,val2,val3] --- creates a list containing the specified values OR var list_name = new List() --- creates a list of size zero
Step 2 − Initializing a List
The index / subscript is used to reference the element that should be populated with a value. The syntax for initializing a list is as given below −
list_name[index] = value;
Example
The following example shows how to create a list of 3 elements.
void main() { var num_list = [1,2,3]; print(num_list); }
It will produce the following output −
[1, 2, 3]
Example
The following example creates a zero-length list using the empty List() constructor. The add() function in the List class is used to dynamically add elements to the list.
void main() { var lst = new List(); lst.add(12); lst.add(13); print(lst); }
It will produce the following output −
[12, 13]
List Properties
The following table lists some commonly used properties of the List class in the dart:core library.
Sr.No | Methods & Description |
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1 | first
Returns the first element in the list.
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2 | isEmpty
Returns true if the collection has no elements.
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3 | isNotEmpty
Returns true if the collection has at least one element.
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4 | length
Returns the size of the list.
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5 | last
Returns the last element in the list.
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6 | reversed
Returns an iterable object containing the lists values in the reverse order.
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7 | Single
Checks if the list has only one element and returns it.
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