How the inheritance of Java should be?

Currently I have admin class, user class and lecturer class. Then I want user and lecturer inherit from user. But the problem is my user class constructor is about the username, password, but the admin and lecturer class constructor I put it with the their profile such as their name, age, gender all those things? Thus, lecture and admin are different with the user class. So is I have something wrong in this?

If you want define class Admin (admin) and Lecturer (lecturer) as User (user), then you can let class Admin and Lecturer inherit from User. But if class Admin and Lecture are not suppose to depend on "username, password", then there is no point in extend from User class. Here is an alternative:

public interface User {
}
public class UserImpl implements User {
private final String username;
private final String password;
public UserImpl(String username, String password) {
this.username = username;
this.password = password;
}
}
public class Admin extends UserGroupAdmin implements User {
protected Admin(String name, int age, String gender) {
super(name, age, gender);
}
}
public class Lecturer extends UserGroupAdmin implements User {
protected Lecturer(String name, int age, String gender) {
super(name, age, gender);
}
}

Make an extra abstract class for common parts:

public abstract class UserGroupAdmin {
private final String name;
private final int age;
private final String gender;
protected UserGroupAdmin(String name, int age, String gender) {
this.name = name;
this.age = age;
this.gender = gender;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
public String getGender() {
return gender;
}
}

Extra reading when it comes to when and when not to inherit: "Liskov Substitution Principle":
https://stackoverflow.com/questions/56860/what-is-an-example-of-the-liskov-substitution-principle

There is more than one way you can accomplish your goal. Here's one :

//base class
abstract class User {
User(String name, int age, ...) {
}
}
class AuthenticatedUser extends User {
AuthenticatedUser(String name, int age..., String username...) {
super(name, age, ...);
//authentication setup next
}
}
class SystemUser extends User {
//etc etc
}

I Guess you want to inherit the user properties to both admin and lecturer class.
So you need to extend the Base class user here.

public class User {
private String username;
private String password;
public User(){
}
}
class Admin extends User{
private String name;
private Integer age;
private String gender;
public Admin(){
//        Constructor code here    
}
}
class Lecturer extends User{
private String name;
private Integer age;
private String gender;
public Lecturer(){
//        Constructor code here
}
}