invoke a superclass constructor

[bill226]

I have to get the subclass to use the superclass constructor, heres my code:

[CODE=java]public class Student
{

// instance variables
private String name;
private int pin;
private boolean newToOU;
private Map<String, List<Integer>> courses;his id the super class


public Student(String aName)
{
super();
Student.counter ++;
this.name = aName;
this.pin = Student.counter ;
this.newToOU = true;
this.courses = new HashMap<String, List<Integer>>( );

this is the subclass

public class StudentAdmin extends Student
{
/* instance variables */
private Map<Integer, String> allStudents;
private Set<Integer> continuingStude nt;
private Set<Integer> newStudent;
public StudentAdmin()
{
super();
this.allStudent s = new TreeMap<Integer , String>();
this.continuing Student = new TreeSet<Integer >();
this.newStudent = new TreeSet<Integer >();[/CODE]

when I compile this code I get an error: cannot find symbol - constructor Student()

Any help would be gratefully accepted

[JosAH]

There's an article in the Java Articles section about the Liskov Substitution Principle.
A StudentAdmin is definitely *not* a student. Your class hierarchy is all wrong.

kind regards,

Jos

[Nepomuk]

[CODE=java]
public class Student
{

// instance variables
private String name;
private int pin;
private boolean newToOU;
private Map<String, List<Integer>> courses;his id the super class


public Student(String aName)
{
super();
Student.counter ++;
this.name = aName;
this.pin = Student.counter ;
this.newToOU = true;
this.courses = new HashMap<String, List<Integer>>( );
[/CODE]
[CODE=java]
public class StudentAdmin extends Student
{
/* instance variables */
private Map<Integer, String> allStudents;
private Set<Integer> continuingStude nt;
private Set<Integer> newStudent;
public StudentAdmin()
{
super();
this.allStudent s = new TreeMap<Integer , String>();
this.continuing Student = new TreeSet<Integer >();
this.newStudent = new TreeSet<Integer >();
}
[/CODE]

when I compile this code I get an error: cannot find symbol - constructor Student()

The Class Student doesn't have a costructor named Student(), only one called Student(String aName). So either have another Constructor in the Student class, or in StudentAdmin() call super("some String");.

[praveen2gupta]

I have to get the subclass to use the superclass constructor, heres my code:

public class Student
{

// instance variables
private String name;
private int pin;
private boolean newToOU;
private Map<String, List<Integer>> courses;his id the super class


public Student(String aName)
{
super();
Student.counter ++;
this.name = aName;
this.pin = Student.counter ;
this.newToOU = true;
this.courses = new HashMap<String, List<Integer>>( );

this is the subclass

public class StudentAdmin extends Student
{
/* instance variables */
private Map<Integer, String> allStudents;
private Set<Integer> continuingStude nt;
private Set<Integer> newStudent;
public StudentAdmin()
{
super();
this.allStudent s = new TreeMap<Integer , String>();
this.continuing Student = new TreeSet<Integer >();
this.newStudent = new TreeSet<Integer >();

when I compile this code I get an error: cannot find symbol - constructor Student()

Any help would be gratefully accepted

Hi
You have not defined the constructor of Student class. For calling the default constructor in the sub classes you should define the default constructor in Student class.

[JosAH]

For calling the default constructor in the sub classes you should define the default constructor in Student class.

That most certainly isn't true: the default ctor of a superclass is called from *any*
ctor in the derived class where no explicit super( ... ) is invoked as its first statement.
Or maybe I completely misunderstood your answer.

kind regards,

Jos

[BigO]

A "default" constructor is only created when no constuctor is explicitly defined. In this case, a constructor is defined, therefore, there is not a no-arg constructor for Student.
Praveen is using the terminology "default constructor" when s/he (sorry) means a "no arg" constructor.
The *no arg* constructor of a superclass is called from *any* ctor in the derived class where no explicit "super" is invoked. This is not necessarily the "default" constructor, it can be a user defined *no arg* constructor.

"nepomuk" provided the correct solution.

[shaileshkumar]

one important point to note:

whether solves your problem or not,

when you inherit a class

constructors are not inherited.