Nsryjdtyk

I'm new to Java and I'm trying to get my head around inheritance.

The error is no suitable constructor found for ClassUser(no arguments) appears at public ClassAdmin(String data) and I haven't found any solutions of help to me.

This is my a snippet of my ClassUser:

public class ClassUser {



public String id;

public String password;

public String name;

public String address;

public String contact;

public String role;





public ClassUser(String id, String password, String name, String address, String contact, String role){



    this.id = id;

    this.password = password;

    this.name = name;

    this.address = address;

    this.contact = contact;

    this.role = role;

}



public ClassUser(String data){

    String dataArray = data.split(",");

    this.id = dataArray[0];

    this.password = dataArray[1];

    this.name = dataArray[2];

    this.address = dataArray[3];

    this.contact = dataArray[4];

    this.role = dataArray[5];

}

This is a snippet of my ClassAdmin:

public class ClassAdmin extends ClassUser{



    public String email;



public ClassAdmin(String id, String password, String name, String contact, 

String email)

{

    super(id+password+name+contact);

    this.email = email;

}

public ClassAdmin(String data){ //problem

    String dataArray = data.split(",");

    this.id = dataArray[0];

    this.password = dataArray[1];

    this.name = dataArray[2];

    this.contact = dataArray[3];

    this.email = dataArray[4];

}

You need to call supper constructor into :

public class ClassAdmin extends ClassUser {



    public String email;



    public ClassAdmin(String id, String password, String name, String contact,

                      String email) {

        super(id + password + name + contact);

        this.email = email;

    }



    public ClassAdmin(String data) { //problem

        super(data);

        String dataArray = data.split(",");



        this.id = dataArray[0];

        this.password = dataArray[1];

        this.name = dataArray[2];

        this.contact = dataArray[3];

        this.email = dataArray[4];

    }

}

Since there is no default constructor present in ClassUser but parameterised constructor present, so while extending the ClassUser you should call

ClassUser(data)

or

ClassUser(String id, String password, String name, String address, String contact, String role)

using super super- java docs

super(data)

or

super(id, password, name, address, contact, role)

You didn't call super() explicitly in the second ClassAdmin constructor so the compiler add super() call without any parameters. You don't have parameterless ClassUser constructor so you are getting the error.

Add explicit super call

public ClassAdmin(String data) {

    super(data.split(",")[0] + data.split(",")[1] + data.split(",")[2] + data.split(",")[3]);

    //...

}

Or use private ClassAdmin constructor to avoid repeating use of data.split(",") (still two uses though)

public ClassAdmin(String data) {

  this(data.split(","));

  //...

}



private ClassAdmin(String dataArray) {

    super(dataArray[0] + dataArray[1] + dataArray[2] + dataArray[3]);

}

Or create parameterless ClassUser constructor

public ClassUser() { }

You need to add invokes of the parent constructor super(data); to the public ClassAdmin(String data) constructor as well.

Because if you don't call parent constructor, you can't create child object. First of all, parent object need to be created. And only after that instantiation of the child object can be executed.

The main reason of the error is that, if you're not providing, explicitly, invocation of the super class constructor, Java compiler tries to find default super class constructor with no argument and in your case there is no default no argument constructor in the ClassUser class.

You can fix in a two ways:

• 
  

  by adding default constructor to the ClassUser:

  
  
  

  public ClassUser() {
  
      //some additional logic 
  
  }
  
  

  
  


• 
  

  by adding call of the super class constructor:

  
  
  

  public ClassAdmin(String data) {
  
      super(data);
  
      String dataArray = data.split(",");
  
      this.id = dataArray[0];
  
      this.password = dataArray[1];
  
      this.name = dataArray[2];
  
      this.contact = dataArray[3];
  
      this.email = dataArray[4];
  
  }
  
  

  
  

It depends on your implementation, but be aware that after you will have called super class constructor, you will have overridden some of the properties in your ClassAdmin constructor.

This is how it works. When you create an instance of Child Class, you need to instantiate member variables of parent/super class as well. If you have a default constructor in Super class then those member variables gets initialized to their default values. If you don't have a default constructor you will have to make a call to parameterized constructor to initialize them. That is why you require a call to super(date) in your ClassAdmin constructor.

Also you don't have to initialize super class member variables like id,password,name etc. in ClassAdmnin constructor. Once you add a super(data) call in this constructor, the member variables of parent class will get initialized in parent class constructor itself.

Moreover your current code will throw NullPointerException as you are getting value from an array based on index without checking the size of array. If you see first constructor of ClassAdmin there is no comma (,) in the string which you are sending to Super class constructor. You can append it like super(id+ "," +password+ "," +name + ","+contact)

public ClassAdmin(String data){

    super(data);   // Add this line and it should fix the problem.

    String dataArray = data.split(",");

    this.id = dataArray[0];

    this.password = dataArray[1];

    this.name = dataArray[2];

    this.contact = dataArray[3];

    this.email = dataArray[4];

}