removeall

Removeall, usually written as removeAll or removeAll(), refers to an operation in programming that deletes every element from a collection that matches a specified criterion. The criterion can be another collection of elements to remove or a predicate that determines which elements should be eliminated. The operation typically mutates the original container and, depending on the language, returns a value indicating the result (such as a boolean or the number of elements removed).

In Java, the standard collection interface provides removeAll(Collection<?> c). It removes all elements from the calling collection that are also contained in the specified collection. It returns true if the collection was changed. The method uses element equality, and performance depends on the internal data structures and the size of both collections.

In C#, List<T> offers RemoveAll(Predicate<T> match), which removes all elements that satisfy the given predicate and returns the number of elements removed. This form is predicate-based rather than collection-based and is commonly used for complex filtering.

Other languages may not have a built-in removeAll method. Python, for example, typically achieves the effect with a filter or a list comprehension that constructs a new list rather than mutating in place. Some libraries provide bulk-remove utilities, while databases perform similar operations via bulk delete queries by criteria.

Common considerations include safety when mutating a collection during iteration, the exact equality semantics used for matching, and whether to perform in-place modification or to create a new collection as an alternative.