record Examples
This page was last reviewed on Jan 21, 2024.
Dot Net Perls
Record. It is possible to add as many class types as necessary for a Java program. But for clarity of the code, and ease of maintenance, using records to reduce code size is possible.
With the record keyword, we can create a class with multiple fields. An optional constructor, with simplified syntax, can also be added for validation.
Example. This Java program defines 3 different records, and then creates one instance of each of them. Records can be defined at the class level, or locally within a method.
Part 1 The ShopEntry record has a String and an int, and it is defined within the Program class. We create an instance of ShopEntry.
Part 2 We define the ShopEntry2 record type locally, and create an instance of it. Records have special code to print out their values.
Part 3 We can specify a constructor on a record. We locally define ShopEntry3 and call toUpperCase in its constructor.
String toLowerCase
public class Program { // Created in main. record ShopEntry (String name, int cost) {} public static void main(String[] args) { // Part 1: create new entry from class-level record. ShopEntry s = new ShopEntry("shoes", 200); System.out.println(s); // Part 2: use local record and create an instance of it. record ShopEntry2 (String name, int size) {} ShopEntry2 s2 = new ShopEntry2("pants", 40); System.out.println(s2); // Part 3: use local record with simplified constructor. record ShopEntry3 (String name, int id) { ShopEntry3 { name = name.toUpperCase(); id = id; } } ShopEntry3 s3 = new ShopEntry3("hat", 30); System.out.println(s3); } }
ShopEntry[name=shoes, cost=200] ShopEntry2[name=pants, size=40] ShopEntry3[name=HAT, id=30]
Some notes. For complicated types with many uses in a program, a class is probably worth creating. But if a type is only used in one place, and is simple, a record is a good option.
Tip We can also use the instanceof operator with records, to determine whether an Object is an instance of a certain record.
Summary. Much like records in other object-oriented programming languages, the records in Java provide a lightweight, low-syntax class type. They can be used like classes in most ways.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Jan 21, 2024 (new).
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