public abstract class Record extends Object
More information about records, including descriptions of the implicitly declared methods synthesized by the compiler, can be found in section 8.10 of The Java Language Specification.
A record class is a shallowly immutable, transparent carrier for a fixed set of values, called the record components. The Java language provides concise syntax for declaring record classes, whereby the record components are declared in the record header. The list of record components declared in the record header form the record descriptor.
A record class has the following mandated members: a canonical constructor, which must provide at least as much access as the record class and whose descriptor is the same as the record descriptor; a private final field corresponding to each component, whose name and type are the same as that of the component; a public accessor method corresponding to each component, whose name and return type are the same as that of the component. If not explicitly declared in the body of the record, implicit implementations for these members are provided.
The implicit declaration of the canonical constructor has the same accessibility as the record class and initializes the component fields from the corresponding constructor arguments. The implicit declaration of the accessor methods returns the value of the corresponding component field. The implicit declaration of the Object.equals(Object), Object.hashCode(), and Object.toString() methods are derived from all of the component fields.
The primary reasons to provide an explicit declaration for the canonical constructor or accessor methods are to validate constructor arguments, perform defensive copies on mutable components, or normalize groups of components (such as reducing a rational number to lowest terms.)
For all record classes, the following invariant must hold: if a record R's components are c1, c2, ... cn, then if a record instance is copied as follows:
R copy = new R(r.c1(), r.c2(), ..., r.cn());
then it must be the case that r.equals(copy).implements Serializable is said to be a serializable record. Serializable records are serialized and deserialized differently than ordinary serializable objects. During deserialization the record's canonical constructor is invoked to construct the record object. Certain serialization-related methods, such as readObject and writeObject, are ignored for serializable records. More information about serializable records can be found in the Java Object Serialization Specification, Section 1.13, "Serialization of Records"., A record class structure can be obtained at runtime via reflection. See Class.isRecord() and Class.getRecordComponents() for more details.| Modifier | Constructor | Description |
|---|---|---|
protected |
Constructor for record classes to call. |
protected Record()
public abstract boolean equals(Object obj)
Object.equals, record classes must further obey the invariant that when a record instance is "copied" by passing the result of the record component accessor methods to the canonical constructor, as follows:
R copy = new R(r.c1(), r.c2(), ..., r.cn());
then it must be the case that r.equals(copy).equals in class Object
true if and only if the argument is an instance of the same record class as this record, and each component of this record is equal to the corresponding component of the argument; otherwise,
false is returned. Equality of a component c is determined as follows: Objects.equals(this.c, r.c) would return true. PW (the corresponding wrapper class for int is
java.lang.Integer, and so on), the component is considered equal if and only if
PW.compare(this.c, r.c) would return 0. obj - the reference object with which to compare.true if this record is equal to the argument; false otherwise.public abstract int hashCode()
Object.hashCode. For records, hashing behavior is constrained by the refined contract of Record.equals, so that any two records created from the same components must have the same hash code.hashCode in class Object
hashCode of its primitive wrapper class.public abstract String toString()
Object.toString(), the toString method returns a string that "textually represents" this record. The result should be a concise but informative representation that is easy for a person to read. In addition to this general contract, record classes must further participate in the invariant that any two records which are equal must produce equal strings. This invariant is necessarily relaxed in the rare case where corresponding equal component values might fail to produce equal strings for themselves.
toString in class Object
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Record.html