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How to sort a Map by keys in Dart

Maria Elijah

To sort a Map, we can utilize the SplayTreeMap. Sorted keys are used to sort the SplayTreeMap.

A SplayTreeMap is a type of map that iterates keys in a sorted order. SplayTreeMap is a self-balancing binary tree. This means that frequently accessed items will be moved closer to the tree’s root.

Syntax

The following is the syntax to declare a SplayTreeMap:

SplayTreeMap map = SplayTreeMap();

Code

The following code shows how to sort a map by key:

import 'dart:collection';

void main() {
  // Creating SplayTreeMap
  var fruits = SplayTreeMap<int, String>();
  
  // Adding key-value pairs
  fruits[1] = 'Orange';
  fruits[4] = 'Banana';
  fruits[6] = 'Pawpaw';
  fruits[3] = 'Apple';
  fruits[5] = 'Mango';
  fruits[2] = 'Avocado';

  print("***Sorted map by keys**");
  print(fruits);

  // Iterating over map pairs using forEach method 
  fruits.forEach((key, val) {
    print('{ key: $key, value: $val}');
  });

}
Using SplayTreeMap for sorting

In thecode above, we created a SplayTreeMap called fruits. By default, the keys are used to sort the pairs, which are sorted numerically and in ascending order.

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