Implementing Factory Pattern and Gettingt NullPointerException, unable to figure out can somebody help me to fix - nullpointerexception

Question

I am posting this code in which I implemented factory method,Code is compiled successfully but null pointer exception occurs at run time and I am unable to figure it out, I know when an object reference points to nothing then this Exception occurs but in my case I am unable to figure out,Can somebody suggest me the fix here I am posting the code.
import java.util.Scanner;
abstract class Plan
{
protected double rate;
public abstract void getRate();
public void calculateBill(int totalUnitsConsume)
{
System.out.println(totalUnitsConsume*rate);
}
}
class DomesticPlan extends Plan
{
public void getRate()
{
rate=3.5;
}
}
class CommercialPlan extends Plan
{
public void getRate()
{
rate=7.50;
}
}
class InstitutionalPlan extends Plan
{
public void getRate()
{
rate=5.50;
}
}
class PlanFactory
{
public static Plan getPlan(String planType)
{
if(planType==null)
{
return null;
}
if (planType.equalsIgnoreCase("DOMESTIC PLAN"))
{
return new DomesticPlan();
}
else if(planType.equalsIgnoreCase("COMMERCIAL PLAN"))
{
return new CommercialPlan();
}
else if (planType.equalsIgnoreCase("INSTITUTION PLAN"))
{
return new InstitutionalPlan();
}
return null;
}
}
public class ElectricityBill
{
public static void main(String ... qwe)
{
int choice;
System.out.println("Choose The Plan type");
System.out.println("1.Domestic Plan");
System.out.println("2.Commercial Plan");
System.out.println("3.Institution Plan");
Scanner sc=new Scanner(System.in);
choice=sc.nextInt();
if(choice>3)
{
System.out.println("Wrong choice entered");
}
else
{
System.out.println("You chose Plan no.:"+ choice);
}
switch(choice)
{
case 1 : Plan p=PlanFactory.getPlan("DomesticPlan");
p.getRate();
p.calculateBill(100);
break;
case 2 : Plan p2=PlanFactory.getPlan("CommercialPlan");
p2.getRate();
p2.calculateBill(300);
break;
case 3 : Plan p3=PlanFactory.getPlan("InstitutionalPlan");
p3.getRate();
p3.calculateBill(250);
break;
default : System.out.println("May be you entered wrong choice");
}
}
}
Output
I:\Data>java ElectricityBill
Choose The Plan type
1.Domestic Plan
2.Commercial Plan
3.Institution Plan
1
You chose Plan no.:1
Exception in thread "main" java.lang.NullPointerException
at ElectricityBill.main(ElectricityBill.java:96)

Answer 1

51. planType.equalsIgnoreCase("DOMESTIC PLAN")
...
96. PlanFactory.getPlan("DomesticPlan")
Here none of the if...else block is getting executed, thus getPlan is returning null.
Please change "DomesticPlan" to "DOMESTIC PLAN" in line 96

Answer 2

You missed a space inside 'DomesticPlanin your code, so your factory can not match any string and returns null, just correct it toDomestic Plan`

Answer 3

It's because your factory is not returning a plan in that case. You are doing PlanFactory.getPlan("DomesticPlan") (no space in DomesticPlan) but within your getPlan method you are looking for "DOMESTIC PLAN" (with space) and therefore Plan p is null. The exception is thrown immediately after, where you are calling the getRate method on the null Plan.
You should null-check when you get a value from the factory, e.g. if (p != null) { p.getRate(); ... }