Record Classes - A Java 16 New Feature

But we don’t want this so we will override one of the functions called toString() and now we run the program it will return the object with its values.

@Override
public String toString() {
    return "Person{" + "id=" + id + ", name='" + name + '\'' + '}';
}

Output: With implementing toString()

Now, what if we create a new object that has the same values i.e the data inside both objects are the same but they differ in memory locations? So we can compare the two objects by comparing two objects with a equals() method of an Object class in Java.

System.out.println(p1.equals(p2)) 

This statement should return “TRUE” but it returns “FALSE”.

The reason they are not the same objects is that they are different objects but with the same values. We know that java doesn’t know so we can tell java when we are comparing, just comparing the values doesn’t compare memory locations. We can do it by overriding equals() and hashcode() methods.

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Person person = (Person) o;
    return id == person.id && Objects.equals(name, person.name);
}
@Override
public int hashCode() {
    return Objects.hash(id, name);
}

And now when we run the program we will get the output “TRUE”.

The whole program can be viewed here.

class Person {
    private int id;
    private String name;
    public Person(int id, String name) {
        this.id = id;
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public String getName() {
        return name;
    }
    @Override
    public String toString() {
        return "Person{" + "id=" + id + ", name='" + name + '\'' + '}';
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return id == person.id && Objects.equals(name, person.name);
    }
    @Override
    public int hashCode() {
        return Objects.hash(id, name);
    }
}
public class PersonClass {
    public static void main(String[] args) {
        Person p1 = new Person(1, "Msft");
        Person p2 = new Person(2, "Msft");
        System.out.println(p1.getName());
        System.out.println(p1.getId());
        System.out.println(p1);
        System.out.println(p2);
        System.out.println(p1.equals(p2));
    }
}

Instead of these lines of code can we use this in a single line so the answer is “YES”.

In Java, if we want to represent a class that on holds data we can create something called “RECORD”.

record Person(int id, String name) {}

Person(int id, String name) here means a parametrized constructor or a canonical constructor.

This record by default has implemented all the methods used inside the above class like getters, toString, hashcode, equals, and others method like these.

Now to confirm if we want to see this record working as above 50 lines of code, we will test it with a simple print statement.

record Person(int id, String name) {
    Person p1 = new Person(1, "Msft");
    Person p2 = new Person(1, "Msft");
    System.out.println(p1);
    System.out.println(p2);
}

Output

Here, without any toString method, we are getting the same results as we are getting by writing huge lines of code.

Summary

With this, we came to the last of this article, and we have some new learnings from this article. But before finishing, we will summarize what we learned.

What did we learn?

• What are Records?
• Why do we need Records?
• Implementation of Records.

GitHub Link: Record Classes