NullPointerException

My assignment is about creating a payroll program.Compiler can compile the program and able to run it,however whenever i enter an email address it produce an error.I've been trying to look for the mistakes but couldnt find it.

Here is the error in command prompt:

Code :

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Exception in thread "main" java.lang.NullPointerException
 
                   at Employee.validateEmail(employee.java:132)
                   at Employee.empdetails(employee.java:110)
                   at Employee.main(employee.java:40)

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source code

Code java:

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import javax.swing.*;
 
 
class Employee{
 
static String details;
static	String name[]= new String [2];
static	int  dobday[]= new int[2];
static	int  dobmth[]= new int[2];
static	int  dobyear[]= new int[2];
static	String ic[]= new String[2];
static	int  adday[]= new int[2];
static	int  admth[]= new int[2];
static	int  adyear[]= new int[2];
static	double  bsalary[]= new double[2];
static	String  email[]= new String [2];
static	String  position[]= new String [2];
static	String  mstatus[]= new String [2];
 
static String z[] = new String[2];
static String z1[] = new String[2];
 
static int dd2;
static int mm2;
static int yyyy2;
static int years[]=new int[2];
 
static double nyallowance[]=new double[2];
static double mrallowance[]=new double[2];
static double costol;
static double netsalary[]=new double[2];
static double epf[]=new double[2];
static String marrystatus;
 
static String emp[]=new String[2];
 
	public static void main(String payroll[]){
 
	empdetails ();
	empid();
	wduration();
	netsalary();
	result();
 
	}
 
	static void empdetails(){
 
	String details;
	int a,b,c,x,j;
 
	for(int k=0;k<2;k++){
 
	name[k]=JOptionPane.showInputDialog("Please Enter Your Full Name");
 
	details=JOptionPane.showInputDialog("Enter your date of birth:DAY");
	dobday[k]=Integer.parseInt(details);
 
 
	if(dobday[k]>31 && dobday[k]<1){
 
		JOptionPane.showConfirmDialog(null,"Wrong Date, Please enter correct date");
 
	}
 
 
	details=JOptionPane.showInputDialog("Enter your date of birth:MONTH");
	dobmth[k]=Integer.parseInt(details);
 
 
	if(dobmth[k]>12 && dobmth[k]<1){
 
		JOptionPane.showConfirmDialog(null,"Wrong Month, Please enter correct Month");
	}
 
 
 
	details=JOptionPane.showInputDialog("Enter your date of birth:YEAR");
	dobyear[k]=Integer.parseInt(details);
 
	ic[k]=JOptionPane.showInputDialog("Enter your Identification Number");
 
	details=JOptionPane.showInputDialog("Enter your appointed date:DAY");
	adday[k]=Integer.parseInt(details);
 
	if(adday[k]>31 && adday[k]<1){
 
		JOptionPane.showConfirmDialog(null,"Wrong Date, Please enter correct date");
	}
 
	details=JOptionPane.showInputDialog("Enter your appointed date:MONTH/(in number not word/)");
	admth[k]=Integer.parseInt(details);
 
	if(admth[k]>12 && admth[k]<1){
 
		JOptionPane.showConfirmDialog(null,"Wrong Month, Please enter correct Month");
 
	}
 
 
	details=JOptionPane.showInputDialog("Enter your appointed date:YEAR");
	adyear[k]=Integer.parseInt(details);
 
	details=JOptionPane.showInputDialog("Enter your basic salary");
	bsalary[k]=Double.parseDouble(details);
 
	details=JOptionPane.showInputDialog("Enter your email address");
 
	validateEmail();
	email[k]=details;
 
 
	position[k]=JOptionPane.showInputDialog("Enter your Position Title");
 
	mstatus[k]=JOptionPane.showInputDialog("Enter your marital status:Married or Not Marry");
 
	z[k]=dobday[k]+"//"+dobmth[k]+"//"+dobyear[k];
	z1[k]=adday[k]+"//"+admth[k]+"//"+adyear[k];
	dd2=adday[k];
	mm2=admth[k];
	yyyy2=adyear[k];
 
	marrystatus=mstatus[k];
	}
	}
 
 
 
	static void validateEmail(){
 
	int h=details.indexOf('@');
	int i=details.lastIndexOf('.');
	int j=details.length();
 
 
	if(h>0){
			if(i!=-1 && i!=(j-1)){
				if(h<i && 1<(i-h)){
 
					JOptionPane.showMessageDialog(null,"Valid email");
				}
					else{
 
					JOptionPane.showMessageDialog(null,"Invalid email");
					}
				}
 
					else{
 
					JOptionPane.showMessageDialog(null,"Invalid email");
					}
				}
					else{
 
					JOptionPane.showMessageDialog(null,"Invalid email");
					}
	}
 
	static void empid(){
 
		String id,num;
 
	int x=0;
 
 
 
 
	for(int i=0; i<2; i++){
 
	if (i<20){
	id="0";
 
	}
	else{
	id="";
	}
 
	if(i>1){
	num="";
	}
	else{
	num="0";
	}
 
	if(i>0){
	x=x+5;
	}
	else{
	x=0;
	}
 
		emp[i]=id+num+x;
 
		System.out.println("EMP"+ emp[i]);
 
 
	}
	}
 
 
	static void wduration(){
 
	int dd1,mm1,yyyy1,years;
 
 
	dd1 = 11;
	mm1 = 11;
	yyyy1 = 2011;
 
	if(yyyy1==yyyy2){
	if(yyyy1>yyyy2){
 
	years=0;
	}
	}
	if (mm1>mm2){
	years=yyyy1-yyyy2;
	}
 
	else{
 
	if (mm1<mm2){
	years=yyyy1-yyyy2-1;
	}
 
	else{
 
	if (mm1==mm2){
 
	if (dd1>dd2){
	years=yyyy1-yyyy2;
	}
	if (dd1<dd2){
	years=yyyy1-yyyy2-1;
	}
	if (dd1==dd2){
	years=yyyy1-yyyy2;
	}
	}
 
	}
 
	}
 
 
 
}
 
 
	static void netsalary(){
 
	//formula Net salary = basic salary+new year allowance+marital allowance+cosf of living - EPF
 
 
	for(int h=0;h<2;h++){
 
	if (bsalary[h]<=10000){
 
	nyallowance[h]=2000;
 
	}
 
	else{
 
	nyallowance[h]=0;
 
	}
 
	if (bsalary[h]>10000 && bsalary[h]<20000){
 
	nyallowance[h]=3000;
 
	}
 
	else{
 
	nyallowance[h]=0;
 
	}
 
	if (bsalary[h]>20000){
 
	nyallowance[h]=5000;
 
	}
 
	else{
 
	nyallowance[h]=0;
 
	}
 
	if (marrystatus.equals("Married")){
 
	mrallowance[h]=4000;
 
	}
 
	else{
 
	mrallowance[h]=0;
 
	}
 
	epf[h]= bsalary[h]*.4;
 
	costol=4500;
 
	netsalary[h]=bsalary[h]+nyallowance[h]+mrallowance[h]+costol+epf[h];
 
}
}
 
 
	static void result(){
 
	for(int n=0;n<2;n++){
 
	System.out.println("Employee ID			:"+emp[n]);
	System.out.println("Name                :"+name[n]);
	System.out.println("Date of Birth       :"+z[n]);
	System.out.println("IC Number           :"+ic[n]);
	System.out.println("Appointed Date      :"+z1[n]);
	System.out.println("Working Duration    :"+years[n]+"Years");
	System.out.println("Position			:"+position[n]);
	System.out.println("Marital Status      :"+mstatus[n]);
	System.out.println("Email               :"+email[n]);
	System.out.println();
	System.out.println("Pay Sheet ---------------------------------");
	System.out.println("\n");
	System.out.println("Basic Salary		:"+bsalary[n]);
	System.out.println("EPF									:"+epf[n]);
	System.out.println("Cost of Living		:"+costol);
	System.out.println("Marital Allowance	:"+mrallowance);
	System.out.println("New Year Allowance	:"+nyallowance);
	System.out.println();
	System.out.println("--------------------------------------------");
	System.out.println("Netsalary: "+netsalary);
	System.out.println("--------------------------------------------");
	}
	}
 
 
 
 
}

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That is waaay too much code for us to wade through. Please shorten it to an SSCCE that demonstrates the problem in as few lines as possible.

Did you google the exception? A NPE is thrown when you attempt to dereference a null reference. This can happen when you try to use a variable that hasn't been set to reference an instance. The stack trace even tells you exactly what line the problem occurs on. Hint: when do you initialize the variable you're trying to use? Add some print statements, or better yet step through this with a debugger, to figure it out.

Someone might be able to help you if you tell us what lines 132,110 and 42 are in your program.

I think that I have figured out what's wrong with your code. You have globally declared a String details object and also another String details object in empdetails() which would hide the global String. And in your program, you are storing the values received from the user in details ( the one declared in empdetials() ) and so the String details declared globally has nothing stored in it. In another method, you are trying to access the Strin details object which isn't initialised yet ( no String value is stored ) Therefore a NullPointerException is thrown. To correct it, simply remove String details varibale from empdetails()

Code :

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static void empdetails(){
 
	// delete this String details;
	int a,b,c,x,j;

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Surprise that we ditched into the one month old topic. Anyway, null pointer exception is the most popular runtime error in Java programming, so it should be taken with care.