Exception in thread "main" java.lang.NullPointerException problem.......
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  1. #1
    Join Date
    Sep 2012
    Posts
    2

    Exclamation Exception in thread "main" java.lang.NullPointerException problem.......

    So when I run this code, I get this "Exception in thread "main" java.lang.NullPointerException" error:


    import feiner.bcs345.health.datetime.*;
    import java.util.*;
    import java.io.*;

    public class datetimetest
    {

    /**
    * @param args
    */
    public static void main(String[] args)
    {
    //*******************************************************************************************
    //MyDate Test
    //*******************************************************************************************
    Scanner s = null;
    PrintStream ps = null;

    MyDate Date1;
    MyDate Date2;



    // New instance using a default constructor.
    Date1 = new MyDate();

    //Set methods alter the values.
    Date1.SetMonth(2);
    Date1.SetDay(2);
    Date1.SetYear(2001);

    //Print statements output the set values to confirm they are correct.
    System.out.print("Month = ");
    System.out.println(Date1.GetMonth());

    System.out.print("Day = ");
    System.out.println(Date1.GetDay());

    System.out.print("Year = ");
    System.out.println(Date1.GetYear());
    System.out.print("\n");



    //New instance using a constructor with parameters.
    Date1 = new MyDate(3, 3, 2002);

    //Print statements output the set values to confirm they are correct.
    System.out.print("Month = ");
    System.out.println(Date1.GetMonth());

    System.out.print("Day = ");
    System.out.println(Date1.GetDay());

    System.out.print("Year = ");
    System.out.println(Date1.GetYear());
    System.out.print("\n");



    //New instance using a constructor with parameters.
    Date1 = new MyDate(4, 4, 2003);

    //Read method reads values set by constructor.
    Date1.Read(s);

    //Write method prints values.
    Date1.Write(ps);


    }

    }





    And Here is the class im using with it:

    package feiner.bcs345.health.datetime;
    import java.util.*;
    import java.io.*;

    public class MyDate
    {
    //Attributes
    private int Month;
    private int Day;
    private int Year;

    //Behaviors
    public int GetMonth() {return Month;}
    public int GetDay() {return Day;}
    public int GetYear() {return Year;}

    public void SetMonth(int m) {Month = m;}
    public void SetDay(int d) {Day = d;}
    public void SetYear(int y) {Year = y;}

    public void Write(PrintStream ps)
    {
    ps.printf("%d\t%d\t%d\t, Month, Day, Year");
    }

    public void Read(Scanner s)
    {
    Month = s.nextInt();
    Day = s.nextInt();
    Year = s.nextInt();
    }

    // Default Constructor
    public MyDate()
    {
    Month = 1;
    Day = 1;
    Year = 2000;
    }

    // Constructor
    public MyDate(int m, int d, int y)
    {
    Month = m;
    Day = d;
    Year = y;
    }
    }





    Can someone please help me make the "Read" and "Write" methods work correctly in main? I think it has something to do with initializing the scanner and/or printstream or something i really don't know i'm a beginner. Thanks in advance

  2. #2
    Join Date
    Sep 2012
    Posts
    2

    Re: Exception in thread "main" java.lang.NullPointerException problem.......

    anyone?

  3. #3
    Join Date
    May 2006
    Location
    UK
    Posts
    4,473

    Re: Exception in thread "main" java.lang.NullPointerException problem.......

    Please use code tags when posting code and also post the full error message and stack trace as it tells us exactly what and where the error is.

    BTW prompting for a reply after waiting only 4 hours is not going to help your question get answered - we all help out here in our spare time so I'm afraid you just have to wait until someone has time to answer your post.
    Posting code? Use code tags like this: [code]...Your code here...[/code]
    Click here for examples of Java Code

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