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How to Combine Lists in Dart?
  • Last Updated : 20 Jul, 2020

In Dart programming, the List data type is similar to arrays in other programming languages. A list is used to represent a collection of objects. It is an ordered group of objects. The core libraries in Dart are responsible for the existence of List class, its creation, and manipulation. There are 5 ways to combine two or more list:

  1. Using addAll() method to add all the elements of another list to the existing list.
  2. Creating a new list by adding two or more lists using addAll() method of the list.
  3. Creating a new list by adding two or more list using expand() method of the list.
  4. Using + operator to combine list.
  5. Using spread operator to combine list.

Using addAll() method to add all the elements of other lists to the existing list

We can add all the elements of the other list to the existing list by the use of addAll() method. To learn about this method you can follow this article.

Example:
 

Dart

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// Main function
main() {
    
  // Creating lists
  List gfg1 = ['Welcome','to'];
  List gfg2 = ['GeeksForGeeks'];
    
  // Combining lists
  gfg1.addAll(gfg2);
    
  // Printing combined list
  print(gfg1);
}

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Output: 



[Welcome, to, GeeksForGeeks]

Creating a new list by adding two or more list using addAll() method of list

We can add all the elements of the list one after another to a new list by the use of addAll() method in Dart. To learn about this method you can follow this article.

Example:
 

Dart

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// Main function
main() {
    
  // Creating lists
  List gfg1 = ['Welcome','to'];
  List gfg2 = ['GeeksForGeeks'];
    
  // Combining lists
  var newgfgList = new List.from(gfg1)..addAll(gfg2);
    
  // Printing combined list
  print(newgfgList);
}

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Output: 

[Welcome, to, GeeksForGeeks]

Creating a new list by adding two or more list using expand() method of list

We can add all the elements of the list one after another to a new list by the use of expand() method in Dart. This is generally used to add more than two lists together.

Example:
 

Dart

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// Main function
main() {
    
  // Creating lists
  List gfg1 = ['Welcome'];
  List gfg2 = ['to'];
  List gfg3 = ['GeeksForGeeks'];
    
  // Combining lists
  var newgfgList = [gfg1, gfg2, gfg3].expand((x) => x).toList();
    
  // Printing combined list
  print(newgfgList);
}

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Output: 



[Welcome, to, GeeksForGeeks]

Using + operator to combine list

We can also add lists together by the use of + operator in Dart. This method was introduced in the Dart 2.0 update.

Example:
 

Dart

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// Main function
main() {
    
  // Creating lists
  List gfg1 = ['Welcome'];
  List gfg2 = ['to'];
  List gfg3 = ['GeeksForGeeks'];
    
  // Combining lists
  var newgfgList = gfg1 + gfg2 + gfg3;
    
  // Printing combined list
  print(newgfgList);
}

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Output: 

[Welcome, to, GeeksForGeeks]

Using spread operator to combine the list

As of Dart 2.3 update, one can also use the spread operator to combine the list in Dart.

Example:
 

Dart

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// Main function
main() {
    
  // Creating lists
  List gfg1 = ['Welcome'];
  List gfg2 = ['to'];
  List gfg3 = ['GeeksForGeeks'];
    
  // Combining lists
  var newgfgList = [...gfg1, ...gfg2, ...gfg3];
    
  // Printing combined list
  print(newgfgList);
}

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Output: 

[Welcome, to, GeeksForGeeks]
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