Overrided hashcode and equals for Privelege class but Set<> contains method still returning false

[Puspender Tanwar]

I have below JPA Entity Privelege

@Getter
@Setter
@Entity
public class Privilege implements Serializable {
    @Id
    @Column(name = "id", unique = true, nullable = false)
    private Byte privilegeId;

    @Column(name = "name", unique = true, nullable = false, length = 45)
    private String name;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        CompanyEmployeePrivilege that = (CompanyEmployeePrivilege) o;
        return Objects.equals(getPrivilegeId(), that.getPrivilegeId());
    }

    @Override
    public int hashCode() {
        return Objects.hash(getPrivilegeId());
    }
}

But when I have an instance of Set<Privilege> on which I want to check if an PrivilegeId exists, I always gets false

final Set<Privilege> privileges = getUserPrivileges(123); //return the privileges of user
return privileges.contains((byte) 1);

In database I have 3 Privileges:
1 CAN_DELETE
2 CAN_ADD
3 CAN_EDIT

Of course, I can do this in another way by iterating over the Set<> and checking the value, but I wanted to try this way as well.

What I am doing wrong? Are equals() and hashcode() correct here?

[Campbell Ritchie]

Please explain how that equals() method works, particularly about the cast in line 16. It looks incorrect to me.
How are instances of your class created? Do you have a default constructor, or have you only shown part of the code?

[Campbell Ritchie]

Why are you seeking a Byte (not a byte) in the Set? You know the Set won't contain it.

[Stephan van Hulst]

As Campbell pointed out, there's a lot of wonkiness here.

1) You can't give different equality definitions for sub-classes. Override equals() once and make it final. The implementation should be based on the current class, not sub-classes. Use instanceof, not getClass().
2) equals() should account for ALL normalized properties of an object, not just a subset. If you want to compare a subset of an object's properties, don't use equals().
3) bytes are not Privileges. You're comparing apples to oranges.
4) It looks like you're using Project Lombok. Stop it. Lombok is a terrible substitute for writing proper type-safe code.
5) Most importantly, don't base your business logic on mutable DTOs. A DTO is only there to facilitate transferring data to and from the database. Convert it to an immutable instance of your business model, which will also contain the equals() implementation.

@Entity
public class PrivilegeData implements Serializable {

  @Id
  @Column(name = "id", unique = true, nullable = false)
  private byte id;

  @Column(name = "name", unique = true, nullable = false, length = 45)
  private String name;

  public PrivilegeData() {}

  public PrivilegeData(Privilege privilege) {
    if (privilege == null)
      throw new ArgumentNullException("The privilege may not be null.");

    this.id   = privilege.id();
    this.name = privilege.name();
  }

  public Privilege toPrivilege() {
    return new Privilege(Byte.toString(id), name);
  }
}

public final class Privilege {

  private final String id;

  private final String name;

  public Privilege(String id, String name) {
    if (id == null)
      throw new IllegalArgumentException("The ID may not be null.");

    if (name == null)
      throw new IllegalArgumentException("The name may not be null.");

    this.id   =   id.strip();
    this.name = name.strip();

    if (this.id.isEmpty() || !this.id.equals(id))
      throw new IllegalArgumentException("The ID must be a non-empty stripped string.");

    if (this.name.isEmpty() || !this.name.equals(name))
      throw new IllegalArgumentException("The name must be a non-empty stripped string.");
  }

  public String id() {
    return id;
  }

  public String name() {
    return name;
  }

  // IMPORTANT: If you decide to make Privilege non-final,
  // then make at least equals() and hashCode() final.
  @Override
  public boolean equals(Object object) {
    if (!(object instanceof Privilege))
      return false;

    var other = (Privilege) object;

    return this.id  .equals(other.id)
        && this.name.equals(other.name);
  }

  @Override
  public int hashCode() {
    return Objects.hash(id, name);
  }
}

Now, even though Privilege has a correct equals() implementation, DON'T use it to compare privileges if you're only interested in the IDs of the privileges. Do this instead:

var privilegeIds = PrivilegeRepository.getAllPrivileges()
  .stream()
  .map(PrivilegeData::toPrivilege)
  .map(Privilege::id)
  .collect(toSet());

return privilegeIds.contains("1");