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Thread: will u tell me why i am getting output "null"

  1. #1
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    Post will u tell me why i am getting output "null"

    public class thread {
    public static void main(String[] args) {

    mythreadprog my1 = new mythreadprog("demo");
    // mythreadprog my2 = new mythreadprog("demo2");

    }
    }



    class personal_details
    {
    String name,mname,lname,course;
    int roll_no;

    void add_details()
    {
    name= "chirag";
    mname="n";
    lname="Shah";
    roll_no= 136;
    course = "Msc";

    }
    void print_details()
    {

    System.out.println(name);
    System.out.println(mname);
    System.out.println(lname);
    System.out.println(roll_no);
    System.out.println(course);

    }
    }




    class mythreadprog implements Runnable
    {
    personal_details p1= new personal_details();
    String threadname;
    Thread t;
    mythreadprog (String name)
    {
    threadname = name;
    t= new Thread(this,"Mydemo");
    //System.out.println(t);
    t.start();

    }


    public void run()
    {

    p1.print_details();

    }
    }


  2. #2
    Junior Member Tjones787's Avatar
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    Default Re: will u tell me why i am getting output "null"

    Your datafield in the personal details class where not initialised.
    And your program did not call the method you use to initialise the variable. That is the add_detail() method in the personal details class.

    That's why u receive a null output. Since there are no object in the your details you asked the program to print.

  3. #3
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    Default Re: will u tell me why i am getting output "null"

    yes, i got it correctly now.
    Thank you.

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    Default Re: will u tell me why i am getting output "null"

    Welcome to the forum! Please read this topic to learn how to post code in code or highlight tags and other useful info for newcomers.

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