java - Syntax error on token "super", invalid Name

I am trying to write the Undergrad class which extends Students

here is the base class (Student)

public class Student{


    private String name;
    private int id;
    private double gpa;

    public Student(){

    }

    public Student(int id, String name, double gpa){
        this.id = id;

        this.name = name;
        this.gpa = gpa;
    }

    public Student(int id, double gpa){
        this(id, "", gpa);
    }

    public String getName(){
        return name;

    }

    public int getId(){
        return id;
    }

    public double getGPA(){
        return gpa;
    }


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

    @Override
    public String toString(){
        return "Student:\nID: " + id + "\nName: " + name + "\nGPA: " + gpa;
    }
}

and here the derived class (Undergrad)

public class Undergrad extends Student {

    private String year;

    public Undergrad (int id , String name ,double gpa,String year)
    {
        super(id,name , gpa);

        this.year =year;

    }

    @Override
    public String toString(){
        return super() + " the year is :" + year;
    }
}

the problem i'm facing is that eclipse shows that I have
a mistake in toString method in class Undergrad
exactly at the super() invoke the error says

"Syntax error on token "super", invalid Name"

could I find any help please ?

Answer

super() call is allowed only in constructors.
you need to call super.toString() if you want to call super class method.

public String toString()
{
      return super.toString() + " the year is :" + year;
 }  

This is the syntax for super keyword
1.for calling a superclass constructor is

1. super(); //the superclass no-argument constructor is called


2. super(parameter list);//the superclass constructor with a matching parameter list is called

2.for calling a superclass member is

1. super.fieldName;//here member is field of super class


2. super.methodName();//here member is method of super class