I order to explain the keyword final that are used with variables. I have attached a file as an example. To solve the error in this file, there are three options. All of them are specified in the file.

Please note that if you declare a primary variable as a final, then this variable will not have a default value.

Run Time errors are detected during the execution of the program Sometimes these are discovered when the user enters an invalid data or data which is not relevant Runtime errors occur when a program does not contain any syntax errors but asks the computer to do something that the computer is unable to reliably do. During compilation the compiler has no technique to detect these kinds of errors. It is the JVM (Java Virtual Machine) which detects it while the program is running..(i did search it on google but this is an abbreviated of what i understood ).

Laith Tawalbeh : Thank you for you answer. But I am looking to know the error in the code. I know that it is a runtime error.

Stack Over Flow error is happening because when line (5) is executed, a new Student is created which in turn tries to execute line(3).

The line (3) again tries to create a new Student object (and hence executes line(3) again) and this keeps going on.

Solution: remove line 3. Because you don't need Student object inside a Student object

Dear Mohammed amer ala-aldden,

First, why have you said "Stack Over Flow"?

Second, I think you should say that:

"The line (5) again tries ..."

instead of saying:

"The line (3) again tries ...".

Best regards.

Dear Nidhal Kamel Taha El-Omari

I run the code on (NetBeans) and the result was an error (Stack Over Flow) . I have read all about it.

This error comes when we make recursive call and it goes to infinite loop, The program will run infinitely until the memory will be exhausted and we will get the (Stack Over Flow Error) .

You are right line(5) as you said.

To avoid this we shall remove one of the line (3) or (5), Then the program will run successfully.

Thanks.

Dear Mohammed amer ala-aldden,

I know that it is a StackOverflowError and it is categorized as a runtime error. I can read the message "Exception in thread "main" java.lang.StackOverflowError at A.Student.(Student.java:3)". Furthermore, I know how to solve the problem; I have written that at the original question: "If you make line 3 or line 5 as a comment, then the code will be run without any error. "

I am asking about the actual reason behind this error.

Dear respected researcher,

The answer to this question is interrelated to the object variable "Osama" which is also:

• An Instance variable.
• Global variable in general.
• An instance of the class "Student".

To prove that try to put a dot after the object "Wasfi" (i.e. Wasfi.) where you will find that the object "Wasfi" takes "Osama" by inheritance. For instance, the following sentence is free of syntax error, but it will give a run time error:

Wasfi.Osama=null; // Wasfi.Osama !!!

Nidhal Kamel Taha El-Omari , Your interpreting for the problem is perfect.

Dear colleagues,

Thanks a lot for your comment and contribution. Really thanks. Thanks for your kindness and support. May Allah protect and bless all of you.

Dear Al'A Togan,

You can't have more than one public class in the same Java file. So, delete the word "public" of the second line or/and of the fourth line. You may also solve the problem by having each class alone in a separate file.

So all the followings are correct:

--------------------------In one file------------------------------------

package Irbid;

class Student {

}

public class TestStudent {

}

---------------------------In one file-----------------------------------

package Irbid;

public class Student {

}

class TestStudent {

}

--------------------------In one file------------------------------------

package Irbid;

class Student {

}

class TestStudent {

}

==============================================

//Now we can have them in two different files.

--------------------------The 1st file----------------------------------

package Irbid;

public class Student {

}

-------------------------The 2nd file-----------------------------------

public class TestStudent {

}