3 ways to remove items to a LinkedHashMap in Dart

How to remove items from a LinkedHashMap in Dart:

In this post, we will learn how to remove a single item or multiple items from a LinkedHashMap in Dart. We can remove a single element or multiple elements by using a given function. Let’s learn how to use these methods with examples.

Method 1: Remove a single element from a LinkedHashMap by using the remove method:

The remove method takes one key as the parameter and it removes the key-value pair with that given key from the LinkedHashMap. The syntax of this method is:

remove(Object? k) → V?

It will look for the key k in the LinkedHashMap and if this is found it removes the key-value pair. It returns the value of the key k before it is removed. If the key is not found, it returns null.

For example,

import 'dart:collection';

void main() {
  final linkedHMap = LinkedHashMap.from({1: 'Mango', 4: 'Banana', 3: 'Orange'});

  print('Given map: ${linkedHMap}');

  linkedHMap.remove(4);

  print('Final LinkedHashMap: ${linkedHMap}');
}

It will print:

Given map: {1: Mango, 4: Banana, 3: Orange}
Final LinkedHashMap: {1: Mango, 3: Orange}

The key-value pair with key 4 is removed from the LinkedHashMap.

Method 2: Remove multiple elements with a given function:

There is another method called removeWhere to remove all elements of a LinkedHashMap as satisfied by a given function. This function is useful to remove multiple items from a LinkedHashMap.

The syntax of this method is:

removeWhere(bool f(K key, V value)) -> void

It takes one function f as the parameter and it removes all entries that are satisfied by this function. The following example removes all entries with even keys:

import 'dart:collection';

void main() {
  final linkedHMap = LinkedHashMap.from({
    1: 'Sun',
    2: 'Mon',
    3: 'Tues',
    4: 'Wed',
    5: 'Thurs',
    6: 'Fri',
    7: 'Sat'
  });

  print('Given LinkedHashMap: ${linkedHMap}');
  linkedHMap.removeWhere((key, value) => key % 2 == 0);
  print('Final LinkedHashMap: ${linkedHMap}');
}

In this example, entries with even keys are removed from the linkedHMap LinkedHashMap. If you run this program, it will print:

Given LinkedHashMap: {1: Sun, 2: Mon, 3: Tues, 4: Wed, 5: Thurs, 6: Fri, 7: Sat}
Final LinkedHashMap: {1: Sun, 3: Tues, 5: Thurs, 7: Sat}

Method 3: Remove all entries of a LinkedHashMap:

The clear() method removes all entries of a given LinkedHashMap. The syntax of the clear method is:

clear() -> void

Let’s try it with an example:

import 'dart:collection';

void main() {
  final linkedHMap = LinkedHashMap.from({
    1: 'Sun',
    2: 'Mon',
    3: 'Tues',
    4: 'Wed',
    5: 'Thurs',
    6: 'Fri',
    7: 'Sat'
  });

  print('Given LinkedHashMap: ${linkedHMap}');
  linkedHMap.clear();
  print('Final LinkedHashMap: ${linkedHMap}');
}

If you run this program, it will print:

Given LinkedHashMap: {1: Sun, 2: Mon, 3: Tues, 4: Wed, 5: Thurs, 6: Fri, 7: Sat}
Final LinkedHashMap: {}

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