6 methods override FieldItemBase::preSave()

AutoIncrementingTestItem::preSave in core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/AutoIncrementingTestItem.php
ChangedItem::preSave in core/lib/Drupal/Core/Field/Plugin/Field/FieldType/ChangedItem.php
DecimalItem::preSave in core/lib/Drupal/Core/Field/Plugin/Field/FieldType/DecimalItem.php
FieldTestItem::preSave in core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/FieldTestItem.php
PasswordItem::preSave in core/lib/Drupal/Core/Field/Plugin/Field/FieldType/PasswordItem.php
PathItem::preSave in core/modules/path/src/Plugin/Field/FieldType/PathItem.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.