Using constructor and using set() for same attributes

Question

I’m studying JPA following the example of uaiContacts.

His project is on Github.

I took the file example modelContact.java:

The class Contact is mapped:

public class Contact {
    @Id
    @GeneratedValue
    private int id;
    private String name;
    private String phoneNumber;
    private String email;
}

and she uses a builder.

public Contact(String name, String phoneNumber, String email, int id) {
    super();
    this.name = name;
    this.phoneNumber = phoneNumber;
    this.email = email;
}

He uses set.

The question is: Why does he use get and set? If the constructor already sets such values when defining an object.

Maybe I shouldn’t just use get?

Remarks:

No inheritance to initialize the constructor; Soon I didn’t understand the super(), since it has no parent class or perhaps some other project class extend this class.

Full model contact. model/Contact.java class code

package uaiContacts.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Contact {

    @Id
    @GeneratedValue
    private int id;
    private String name;
    private String phoneNumber;
    private String email;

    public Contact(){

    }

    public Contact(String name, String phoneNumber, String email, int id) {
        super();
        this.name = name;
        this.phoneNumber = phoneNumber;
        this.email = email;
    }

public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPhoneNumber() {
        return phoneNumber;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

@Override
    public boolean equals(Object object) {
        if (object instanceof Contact){
            Contact contact = (Contact) object;
            return contact.id == id;
        }

        return false;
    }

    @Override
    public int hashCode() {
        return id;
    }
}

Take, if you prefer, the code on github:

https://github.com/uaihebert/uaicontacts

Answer 1

Why does it use get and set? If the constructor already arrow such values when we define an object. [...] Maybe you shouldn’t just use get?

The set is for updating the entity’s information, since it already uses the constructor to instantiate the entity’s information. The get is for information to be available.

Otherwise, there would be no need set nor the get, because JPA requires neither one nor the other.

No inheritance to initialize the constructor super(), since it has no parent class or perhaps some other class of the project extend this class.

In this case, it’s really unnecessary.

Recalling that the JPA always demands a constructor without arguments.