# Serial Added in[API level 34](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) # Serial ``` @Target([AnnotationTarget.FUNCTION, AnnotationTarget.PROPERTY_GETTER, AnnotationTarget.PROPERTY_SETTER, AnnotationTarget.FIELD]) class Serial ``` |----------------------------------------------------------------------------------| | [java.io.Serial](https://developer.android.com/reference/kotlin/java/io/Serial#) | Indicates that an annotated field or method is part of the[serialization mechanism](https://developer.android.com/reference/kotlin/java/io/Serializable)defined by the Java Object Serialization Specification. This annotation type is intended to allow compile-time checking of serialization-related declarations, analogous to the checking enabled by the[java.lang.Override](https://developer.android.com/reference/kotlin/java/lang/Override.html#)annotation type to validate method overriding. classes are encouraged to use annotations to help a compiler catch mis-declared serialization-related fields and methods, mis-declarations that may otherwise be difficult to detect. Specifically, annotations of this type should be applied to serialization-related methods and fields in classes declared to be`Serializable`. The five serialization-related methods are: - `private void writeObject(java.io.ObjectOutputStream stream) throws IOException` - `private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException` - `private void readObjectNoData() throws ObjectStreamException` - *ANY-ACCESS-MODIFIER* `Object writeReplace() throws ObjectStreamException` - *ANY-ACCESS-MODIFIER* `Object readResolve() throws ObjectStreamException` The two serialization-related fields are: - `private static final ObjectStreamField[] serialPersistentFields` - `private static final long serialVersionUID` Compilers are encouraged to validate that a method or field marked with a`@Serial`annotation is one of the defined serialization-related methods or fields declared in a meaningful context and issue a warning if that is not the case. It is a semantic error to apply this annotation to other fields or methods, including: - fields or methods in a class that is not`Serializable` - fields or methods of the proper structural declaration, but in a type where they are ineffectual. For example,`enum`types are defined to have a`serialVersionUID`of`0L`so a`serialVersionUID`field declared in an`enum`type is ignored. The five serialization-related methods identified above are likewise ignored for an`enum`type. - in a class that is`Externalizable`: - method declarations of`writeObject`,`readObject`, and`readObjectNoData` - a field declaration for`serialPersistentFields` While the`Externalizable`interface extends`Serializable`, the three methods and one field above are*not*used for externalizable classes. Note that serialization mechanism accesses its designated fields and methods reflectively and those fields and methods may appear otherwise unused in a`Serializable`class. ## Summary | Public constructors || |------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---| | [Serial](https://developer.android.com/reference/kotlin/java/io/Serial#Serial())`()` Indicates that an annotated field or method is part of the[serialization mechanism](https://developer.android.com/reference/kotlin/java/io/Serializable)defined by the Java Object Serialization Specification. | ## Public constructors ### Serial Added in[API level 34](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) ``` Serial() ``` Indicates that an annotated field or method is part of the[serialization mechanism](https://developer.android.com/reference/kotlin/java/io/Serializable)defined by the Java Object Serialization Specification. This annotation type is intended to allow compile-time checking of serialization-related declarations, analogous to the checking enabled by the[java.lang.Override](https://developer.android.com/reference/kotlin/java/lang/Override.html#)annotation type to validate method overriding. classes are encouraged to use annotations to help a compiler catch mis-declared serialization-related fields and methods, mis-declarations that may otherwise be difficult to detect. Specifically, annotations of this type should be applied to serialization-related methods and fields in classes declared to be`Serializable`. The five serialization-related methods are: - `private void writeObject(java.io.ObjectOutputStream stream) throws IOException` - `private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException` - `private void readObjectNoData() throws ObjectStreamException` - *ANY-ACCESS-MODIFIER* `Object writeReplace() throws ObjectStreamException` - *ANY-ACCESS-MODIFIER* `Object readResolve() throws ObjectStreamException` The two serialization-related fields are: - `private static final ObjectStreamField[] serialPersistentFields` - `private static final long serialVersionUID` Compilers are encouraged to validate that a method or field marked with a`@Serial`annotation is one of the defined serialization-related methods or fields declared in a meaningful context and issue a warning if that is not the case. It is a semantic error to apply this annotation to other fields or methods, including: - fields or methods in a class that is not`Serializable` - fields or methods of the proper structural declaration, but in a type where they are ineffectual. For example,`enum`types are defined to have a`serialVersionUID`of`0L`so a`serialVersionUID`field declared in an`enum`type is ignored. The five serialization-related methods identified above are likewise ignored for an`enum`type. - in a class that is`Externalizable`: - method declarations of`writeObject`,`readObject`, and`readObjectNoData` - a field declaration for`serialPersistentFields` While the`Externalizable`interface extends`Serializable`, the three methods and one field above are*not*used for externalizable classes. Note that serialization mechanism accesses its designated fields and methods reflectively and those fields and methods may appear otherwise unused in a`Serializable`class. **See Also** - [java.io.Serializable](https://developer.android.com/reference/kotlin/java/io/Serializable) - [java.io.Externalizable](https://developer.android.com/reference/kotlin/java/io/Externalizable)