Thread: My encounter with Mrs. NullPointerException

Hello companions,

I've been working on a phone customer billing program for a few days now and I've been able to make considerable progress thanks to the aid of the members on this forum and the Oracle Java reference site. Yesterday, I made some minor changes to my Eclipse layout and basically from there I just started minimizing and maximizing and removing aspects of the interface unknowingly.

Regardless, I have experienced a Null Pointer Exception and I've been doing the best debugging process I've ever done in my life. I still can't locate the resource or tip to help me get back on the right track.

This is the program I am still working on;

First Post (provides concept of program)

This is my updated code;

package spInputOutput;
 
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
 
public class spInputOutput {
 
	public static PrintWriter outputStream;
 
	public static void main(String[] args) throws IOException
	{
		readData();
	}
 
	public static void readData() throws IOException
	{
		//Monthly Base Fee of $20
		double monthlyBase = 20;
		double startTime = 0.00;
		double duration = 0.00;
		//double amountDue = monthlyBase + (duration * startTime);
 
		//ArrayList<Double> amtDue = new ArrayList<Double>();
		ArrayList <String> accts = new ArrayList<String>();
		//use 'contains' to check whether or not the account number has been accounted for, add or create new instance
 
		double daytimeCall = 0.12; /*per minute for calls that started between 8:00 AM and 10:00PM, 
		inclusive $0.05 per minute all other times*/
 
		FileReader fr = new FileReader("input_data.txt");
		BufferedReader br = new BufferedReader(fr);
 
		String invoice = "invoice.txt";
        try {
			outputStream = new PrintWriter(invoice);
		}
        catch (FileNotFoundException e) {
			e.printStackTrace();
		}
 
		//String[] a = line.split(":"); for times
 
        outputStream.println("Invoice");
        outputStream.println("**********");
        outputStream.println("");
        outputStream.println("Account");
        outputStream.println("");
        outputStream.println("Amount Due");
        //Should eventually use algorithm to calculate the amounts due for each account
 
        /*
         Created to simulate values for Amounts Due
 
         for(int i=1; i<4; i++)
        {
        	double z = ((10+(i*2))+(i*(Math.random())));
        	outputStream.printf("%.2f", z);  
        	outputStream.println("\n"); 
        }
        */
 
        outputStream.println("");
        outputStream.println("**********");
        outputStream.println("Total:");
 
        String text = "";
        String line = br.readLine();
 
		while(line != null)
		{
			text += line;
			line = br.readLine();
 
                        //THE LINE BELOW IS WHERE MY PROGRAM IDENTIFIES THE NULL POINTER EXCEPTION
			String [] a = line.split(" ");
 
			//Account numbers loop
			for(int i=0; i<1; i++)
			{
				//If account number is already in array if()
				accts.add(a[i]);
				outputStream.println(a[i]);
			}		
		}
 
		System.out.println(text);
 
		System.out.println("Inovice File Incorrectly Created");
		System.out.println(accts.get(1));
 
		outputStream.close();
		br.close();
 
	}
}

This is the message displayed in the console after attempting to run;

Exception in thread "main" java.lang.NullPointerException
at spInputOutput.spInputOutput.readData(spInputOutput .java:79)
at spInputOutput.spInputOutput.main(spInputOutput.jav a:18)

As always, I am grateful for assistance. Any suggestions are welcome, thanks.

Very good explanation.