A record is a concise way to define a class that holds data. Java automatically provides a constructor, accessor methods, and implementations of equals(), hashCode(), and toString().
In this example, you will create a Book record to store a title and an author.
Source code
Save the following code as RecordExample.java:
public class RecordExample {
void main() {
Book firstBook = new Book("Learning Java", "Alice");
Book secondBook = new Book("Learning Java", "Alice");
IO.println("Title: " + firstBook.title());
IO.println("Author: " + firstBook.author());
IO.println("Record: " + firstBook);
IO.println("Equal values: " + firstBook.equals(secondBook));
IO.println("Same object: " + (firstBook == secondBook));
}
}
record Book(String title, String author) {
}
Explanation
The following declaration defines a record with two components:
record Book(String title, String author) {
}
The components are title and author, both of type String.
For this declaration, Java automatically provides:
| Member | Purpose |
|---|---|
Book(String title, String author) |
Initializes the components |
title() |
Returns the title |
author() |
Returns the author |
equals(Object other) |
Compares component values |
hashCode() |
Calculates a hash code from the components |
toString() |
Returns a text representation of the record |
Creating a record object
Use the new keyword and pass a value for each component:
Book firstBook = new Book("Learning Java", "Alice");
The arguments follow the order of the components in the record declaration.
Reading component values
Record accessors use the component names directly:
firstBook.title()
firstBook.author()
The generated methods are named title() and author(), rather than getTitle() and getAuthor().
Each component has a private final field. Records do not generate setters, so you cannot reassign these fields after construction.
Comparing records
The example creates two separate objects with the same component values:
Book firstBook = new Book("Learning Java", "Alice");
Book secondBook = new Book("Learning Java", "Alice");
The generated equals() method returns true because both objects are instances of the same record class and have equal component values.
The == operator returns false because the variables refer to separate objects.
Printing a record
Passing the record to IO.println() uses its generated toString() method:
IO.println("Record: " + firstBook);
The result includes the record name, component names, and their values.
Run the example
Compile and run the file:
javac RecordExample.java
java RecordExample
Output
Title: Learning Java
Author: Alice
Record: Book[title=Learning Java, author=Alice]
Equal values: true
Same object: false
Are records immutable?
Records are shallowly immutable: their component fields cannot be reassigned, but referenced objects may still be mutable.
This Book record contains only strings, which are immutable. If a record contains a mutable list or array, additional steps are needed to protect that data from changes.