[Term Entry] Dart Queue: .retainWhere() #8149

content/dart/concepts/queue/terms/retainWhere/retainWhere.md

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+---
+Title: '.retainWhere()'
+Description: 'Retains only the elements that satisfy a given condition.'
+Subjects:
+  - 'Computer Science'
+  - 'Code Foundations'
+Tags:
+  - 'Dart'
+  - 'Methods'
+  - 'Queues'
+CatalogContent:
+  - 'learn-dart'
+  - 'paths/computer-science'
+---
+
+The **`.retainWhere()`** method removes all elements from a `Queue` that do not satisfy the given condition, keeping only the elements for which the condition returns `true`.
+
+## Syntax
+
+```pseudo
+queue.retainWhere(test)
+```
+
+**Parameters:**
+
+- `test` (bool Function(E element)): A function that returns `true` for elements that should be retained in the queue.
+
+**Return value:**
+
+Returns `void`. The original queue is updated by retaining only the matching elements.
+
+## Example: Retaining elements in a queue based on a condition
+
+In this example, a queue is created and populated with integers. The `.retainWhere()` method is then used to keep only the elements that are less than 4:
+
+```dart
+import 'dart:collection';
+
+void main() {
+  Queue<int> example_queue = Queue<int>();
+
+  example_queue.addAll([1, 3, 5, 2, 0]);
+
+  // Keep elements less than 4
+  example_queue.retainWhere((element) => element < 4);
+
+  print("The queue with the correct numbers is: $example_queue");
+}
+```
+
+The above code will give the following output:
+
+```shell
+The queue with the correct numbers is: {1, 3, 2, 0}
+```