Thread: Request Information

Hi Mates,

I am extremely new to java. I just started learning the basics. I am stuck with the following piece of code. Could someone please tell me where I went wrong?

Code goes here!!!!!

package trialdate;

public class TrialDate {

private int month;
private int year;
TrialDate hiredate;
public TrialDate(){

System.out.println("Here goes nothing!!!!!");

}
public TrialDate(int month, int year){

hiredate.month = month;
hiredate.year = year;
System.out.println("The month and year is " + hiredate.month+" "+ hiredate.year);
}
public void myTrial(){

hiredate = new TrialDate(12, 2008);

}
public static void main(String[] args) {
TrialDate newDate = new TrialDate();
newDate.myTrial();
}
}

I just want to learn the concept pass by reference
The out put of the program is

Here goes nothing!!!!!
Exception in thread "main" java.lang.NullPointerException
at trialdate.TrialDate.<init>(TrialDate.java:19)
at trialdate.TrialDate.myTrial(TrialDate.java:25)
at trialdate.TrialDate.main(TrialDate.java:30)
Java Result: 1

Your error is in the constructor with two integers. In the beginning you made the variables month and year private and in your constructor you try and access them as if they were public. To fix this, either make your variables public or make two methods that return month and year so that you can access them even though they are private. The reason you got a NullPointerException is that when you call hiredate.month it is looking for a public integer named month in the TrialDate class and can't find one. I hope this was helpful.