How to use Records class in Java 14 to create mutable data objects

How to use Records class to create mutable data objects in Java 14

Introduction:
Java 14 is the latest version of the Java programming language, which introduces the Records class as a new data type . The Records class provides a concise way to create immutable data objects. In this article, we will introduce how to use Records class to create mutable data objects in Java 14 and provide corresponding code examples.

1. Introduction to the Records class
The Records class is a new data class added in Java 14. It is mainly used to represent immutable data objects. The Records class will automatically generate some commonly used methods for us, such as equals(), hashCode() and toString() methods, thereby reducing the need for us to write repeated code. Compared with ordinary classes, the Records class is final and is not allowed to be inherited or modify the accessibility of properties.

2. Use the Records class to create mutable data objects
If we want to create a mutable data object, compared to immutable objects, we can use the mutable attribute of the Records class to achieve it. Here is a sample code:

public record Person(String name, int age) {
    public Person {
        if (age < 0) {
            throw new IllegalArgumentException("age should be non-negative");
        }
    }
    public void setAge(int age) {
        if (age < 0) {
            throw new IllegalArgumentException("age should be non-negative");
        }
        this.age = age;
    }
}

In the above example, we created a Person class and declared it as Records class. By adding legality checks for properties in the constructor, we can ensure that the objects we create are valid. At the same time, we added a setAge() method to allow modification of the age attribute. In this way, we create a mutable Person object.

3. Use the Records class to create objects
For variable Person objects, we can create them in the following way:

Person person = new Person("Alice", 30);
System.out.println(person.name()); // 输出：Alice
System.out.println(person.age()); // 输出：30

person.setAge(31);
System.out.println(person.age()); // 输出：31

In the above code, we use the constructor of the Person class to create A Person object was obtained, and the name() and age() methods were called respectively to obtain the corresponding attribute values. Next, we modify the value of the age attribute by calling the setAge() method. Through the output, we can see that the value of the age attribute has been successfully modified.

4. Notes on the Records class
Although the Records class provides convenient functions, you also need to pay attention to some restrictions when using it:

1. The Records class is final. Not allowed to be inherited.
2. The properties of the Records class are final by default and are not allowed to be modified.
3. The constructor of the Records class is private by default.
4. The equals(), hashCode() and toString() methods automatically generated by the Records class compare according to attributes by default.

Summary:
In Java 14, the Records class provides us with a concise way to create immutable data objects. By setting the mutable attribute, we can also create mutable data objects. Using the Records class can reduce our workload of writing repeated code and improve the readability and maintainability of the code. I believe that with the widespread application of Java 14, the Records class will play an increasingly important role in future Java development.

Reference link:
[1] https://openjdk.java.net/jeps/359

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