description

# contains method Null safety

bool contains (

1. Object? element

)
inherited

Returns true if the collection contains an element equal to `element`.

This operation will check each element in order for being equal to `element`, unless it has a more efficient way to find an element equal to `element`.

The equality used to determine whether `element` is equal to an element of the iterable defaults to the Object.== of the element.

Some types of iterable may have a different equality used for its elements. For example, a Set may have a custom equality (see Set.identity) that its `contains` uses. Likewise the `Iterable` returned by a Map.keys call should use the same equality that the `Map` uses for keys.

## Implementation

    bool contains(Object? element) {
      int length = this.length;
      for (int i = 0; i < length; i++) {
        if (elementAt(i) == element) return true;
        if (length != this.length) {
          throw new ConcurrentModificationError(this);
        }
      }
      return false;
    }