30 files declare their use of FormatterBase

DatetimeDefaultFormatter.php in drupal/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimeDefaultFormatter.php: Contains \Drupal\datetime\Plugin\field\formatter\DateTimeDefaultFormatter.
DatetimePlainFormatter.php in drupal/core/modules/datetime/lib/Drupal/datetime/Plugin/field/formatter/DatetimePlainFormatter.php: Contains \Drupal\datetime\Plugin\field\formatter\DateTimePlainFormatter.
DefaultNumberFormatter.php in drupal/core/modules/number/lib/Drupal/number/Plugin/field/formatter/DefaultNumberFormatter.php: Contains \Drupal\number\Plugin\field\formatter\DefaultNumberFormatter.
EntityReferenceFormatterBase.php in drupal/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/formatter/EntityReferenceFormatterBase.php: Contains \Drupal\entity_reference\Plugin\field\formatter\EntityReferenceFormatterBase.
GenericFileFormatter.php in drupal/core/modules/file/lib/Drupal/file/Plugin/field/formatter/GenericFileFormatter.php: Contains \Drupal\file\Plugin\field\formatter\GenericFileFormatter.
ImageFormatter.php in drupal/core/modules/image/lib/Drupal/image/Plugin/field/formatter/ImageFormatter.php: Contains \Drupal\image\Plugin\field\formatter\ImageFormatter.
LinkFormatter.php in drupal/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkFormatter.php: Contains \Drupal\link\Plugin\field\formatter\LinkFormatter.
LinkFormatter.php in drupal/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/formatter/LinkFormatter.php: Contains \Drupal\taxonomy\Plugin\field\formatter\LinkFormatter.
LinkSeparateFormatter.php in drupal/core/modules/link/lib/Drupal/link/Plugin/field/formatter/LinkSeparateFormatter.php: Contains \Drupal\link\Plugin\field\formatter\LinkSeparateFormatter.
MailToFormatter.php in drupal/core/modules/email/lib/Drupal/email/Plugin/field/formatter/MailToFormatter.php: Definition of Drupal\email\Plugin\field\formatter\MailToFormatter.
NumberDecimalFormatter.php in drupal/core/modules/number/lib/Drupal/number/Plugin/field/formatter/NumberDecimalFormatter.php: Definition of Drupal\number\Plugin\field\formatter\NumberDecimalFormatter.
NumberIntegerFormatter.php in drupal/core/modules/number/lib/Drupal/number/Plugin/field/formatter/NumberIntegerFormatter.php: Definition of Drupal\number\Plugin\field\formatter\NumberIntegerFormatter.
NumberUnformattedFormatter.php in drupal/core/modules/number/lib/Drupal/number/Plugin/field/formatter/NumberUnformattedFormatter.php: Definition of Drupal\number\Plugin\field\formatter\NumberUnformattedFormatter.
OptionsDefaultFormatter.php in drupal/core/modules/options/lib/Drupal/options/Plugin/field/formatter/OptionsDefaultFormatter.php: Contains \Drupal\options\Plugin\field\formatter\OptionsDefaultFormatter.
OptionsKeyFormatter.php in drupal/core/modules/options/lib/Drupal/options/Plugin/field/formatter/OptionsKeyFormatter.php: Contains \Drupal\options\Plugin\field\formatter\OptionsKeyFormatter.
PictureFormatter.php in drupal/core/modules/picture/lib/Drupal/picture/Plugin/field/formatter/PictureFormatter.php: Contains \Drupal\picture\Plugin\field\formatter\PictureFormatter.
PlainFormatter.php in drupal/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/formatter/PlainFormatter.php: Contains \Drupal\taxonomy\Plugin\field\formatter\PlainFormatter.
RSSCategoryFormatter.php in drupal/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/formatter/RSSCategoryFormatter.php: Contains \Drupal\taxonomy\Plugin\field\formatter\RSSCategoryFormatter.
RSSEnclosureFormatter.php in drupal/core/modules/file/lib/Drupal/file/Plugin/field/formatter/RSSEnclosureFormatter.php: Contains \Drupal\file\Plugin\field\formatter\RSSEnclosureFormatter.
TableFormatter.php in drupal/core/modules/file/lib/Drupal/file/Plugin/field/formatter/TableFormatter.php: Contains \Drupal\file\Plugin\field\formatter\TableFormatter.
TaxonomyFormatterBase.php in drupal/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/formatter/TaxonomyFormatterBase.php: Contains \Drupal\taxonomy\Plugin\field\formatter\TaxonomyFormatterBase.
TelephoneLinkFormatter.php in drupal/core/modules/telephone/lib/Drupal/telephone/Plugin/field/formatter/TelephoneLinkFormatter.php: Contains \Drupal\telephone\Plugin\field\formatter\TelephoneLinkFormatter.
TestFieldDefaultFormatter.php in drupal/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldDefaultFormatter.php: Contains \Drupal\field_test\Plugin\field\formatter\TestFieldDefaultFormatter.
TestFieldEmptyFormatter.php in drupal/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldEmptyFormatter.php: Contains \Drupal\field_test\Plugin\field\formatter\TestFieldEmptyFormatter.
TestFieldMultipleFormatter.php in drupal/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldMultipleFormatter.php: Contains \Drupal\field_test\Plugin\field\formatter\TestFieldMultipleFormatter.
TestFieldPrepareViewFormatter.php in drupal/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Plugin/field/formatter/TestFieldPrepareViewFormatter.php: Contains \Drupal\field_test\Plugin\field\formatter\TestFieldPrepareViewFormatter.
TextDefaultFormatter.php in drupal/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextDefaultFormatter.php: Definition of Drupal\text\Plugin\field\formatter\TextDefaultFormatter.
TextPlainFormatter.php in drupal/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextPlainFormatter.php: Definition of Drupal\text\Plugin\field\formatter\TextPlainFormatter.
TextTrimmedFormatter.php in drupal/core/modules/text/lib/Drupal/text/Plugin/field/formatter/TextTrimmedFormatter.php: Contains \Drupal\text\Plugin\field\formatter\TextTrimmedFormatter.
UrlPlainFormatter.php in drupal/core/modules/file/lib/Drupal/file/Plugin/field/formatter/UrlPlainFormatter.php: Contains \Drupal\file\Plugin\field\formatter\UrlPlainFormatter.