java program compiles with no error but does not run

Question

Here is my code after changes suggested by stackoverflow members. The code compiles with no errors but when I run "java Realtor11", I get the following errors. I am importing the correct libraries so not sure what the issue is.

The goal of the program is to read two values (first line is a string (John) and the second line is a double (100)) and output them with some calculations to a JOption message.

Exception in thread "main" java.lang.NullPointerException at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) at java.lang.Double.parseDouble(Unknown Source) at Realtor11.main(Realtor11.java:49)

// java class for keyboard I/O
import java.util.Scanner;
// java class for JOption GUI
import javax.swing.JOptionPane;
// File reader
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;

public class Realtor11
{
    public static void main(String[] args)
    {
    // Keyboard and file input
        Scanner console = new Scanner(System.in); 
        Scanner inputStream = null;
    // price of the house, the cost to sell the house and the commission
        double price = 0;
        double cost, commission;
    // seller's name
        String seller = "name";



// GUI diplay message declaration
    String display_message = "This program calculates the cost to sell a home\n" 
    + "and the commission paid to an individual sales agent.\n\n"
    + "The user is asked for the last name of the seller and the\n"
    + "sales price.\n\n";

// Output descriptive messages
    JOptionPane.showMessageDialog(null, display_message, "Lab 1 Description", JOptionPane.INFORMATION_MESSAGE);

// Read Realtor11.txt
    try {
        BufferedReader in = new BufferedReader(new FileReader("Realtor11.txt"));
        while (in.read()!= -1);
        seller = in.readLine();
        price = Double.parseDouble(in.readLine());
        in.close();
        } 

        catch (IOException e) {}


// calculate the cost and the commission
    cost = 0.06 * price;
    commission = 0.015 * price;
// display the input and results
    String 
        out1 = String.format("%nThe " + seller + "'s" + " home sold for $%.2f%n", price),
        out2 = String.format("The cost to sell the home was $%.2f%n", cost),
        out3 = String.format("The selling or listing agent earned $%.2f%n", commission);

    JOptionPane.showMessageDialog(null, out1 + out2 + out3, seller + "'s Home Sale", JOptionPane.INFORMATION_MESSAGE);

// Output to file
// still writing this. 

}

}

Time to do a little debugging. Consider using a debugger or sprinkle your code with lots of printlns. — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Jan 28, 2014 at 21:37
Just FYI - I explicitly declare variables 'price' and 'seller' since I was getting compile errors. But I assume that should not matter since the variables would bu updated based on the contents of the text file. — ismail_1
– ismail_1, Commented Jan 28, 2014 at 21:38
A NullPointerException is thrown when an application attempts to use null in a case where an object is required: docs.oracle.com/javase/7/docs/api/java/lang/… As @HovercraftFullOfEels suggested you should debug your application. — Miguel Jiménez
– Miguel Jiménez, Commented Jan 28, 2014 at 21:39
isn't the error self-explaining? you know the error, you know the line number and you can check what causes this type of error. try debugging. — alex
– alex, Commented Jan 28, 2014 at 21:39

Dawood ibn Kareem · Accepted Answer · 2014-01-28 21:40:25Z

3

The problem is this line.

while (in.read()!= -1);

This is kind of a "degenerate loop" because of the semicolon at the end. It continues to read from the file until there's nothing left to be read. After that, there are no double values to parse.

answered Jan 28, 2014 at 21:40

Dawood ibn Kareem

80.2k15 gold badges102 silver badges112 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

ismail_1 Over a year ago

True and I fixed this. Still the same error. I am working through the other comments. I am new to this so will keep researching.

Marenthyu Over a year ago

Good eye David. I wouldn't have recognised that.

Dawood ibn Kareem Over a year ago

OK, how did you fix it? What is your call to Double.parseDouble seeing now? It's a bit hard to debug partially-fixed code, without seeing what the fix is.

Axel Amthor Over a year ago

Guess you just deleted the ; which means he reads "sellers" until the EOF and the Double.parseDouble still gets a null because of EOF already reached ...

Dawood ibn Kareem Over a year ago

Yes, that seems quite likely.

|

Axel Amthor · Accepted Answer · 2014-01-28 21:44:30Z

2

These three lines cause the error:

    while (in.read()!= -1);           // this reads until EOF
    seller = in.readLine();           // this gets a null-pointer since we're behind EOF
    price = Double.parseDouble(in.readLine()); // same as above, This is the printed error.

That should probably be:

    seller = in.readLine();  // first line: seller
    price = Double.parseDouble(in.readLine()); // second line: price

This can be improved:

    seller = in.readLine();  // first line: seller
    String sPrice = in.readLine(); // second line: price
    if ( sPrice != null )
        price = Double.parseDouble(sPrice);

answered Jan 28, 2014 at 21:44

Axel Amthor

11.1k1 gold badge28 silver badges45 bronze badges

1 Comment

ismail_1 Over a year ago

Thank you Axel for EOF statement. Now I understand why the values would not process after the first line.

JB Nizet · Accepted Answer · 2014-01-28 21:43:29Z

1

Look at this code:

while (in.read()!= -1);
seller = in.readLine();
price = Double.parseDouble(in.readLine());
in.close();

The first line reads everything from the reader, without doing anything with what it reads. Then, when everything has been read, you're trying to read a line again. That will obviously return null, since you've already read everything. And then you're trying to read a line again (which of course continues to return null), and parse this null to a double.

And at the end, you close the reader, but since you don't do it in a finally block, the NPE that is thrown before prevents it to be closed.

I think it's time for you to read the javadoc of the methods you're using, and the Java IO tutorial.

Also, avoid this like the plague:

catch (IOException e) {}

You're simply hiding the exception from yourself, making any diagnostic impossible if an IOException occurs.

answered Jan 28, 2014 at 21:43

JB Nizet

694k94 gold badges1.3k silver badges1.3k bronze badges

1 Comment

ismail_1 Over a year ago

I will be honest. I did not even research on the "exception" part. I was concentrating on the upper portion of grabbing the values from the ext file. In the future, I will keep this in mind.

Logan Murphy · Accepted Answer · 2014-01-28 21:44:52Z

0

There is a difference between compile errors and runtime errors (which this is).

try this instead of the while loop

String line = in.readLine();
if(line != null) {
    seller = line;
}
line = in.readLine();
if(line != null) {
    price = Double.parseDouble(line);
}
in.close();

edited Jan 28, 2014 at 21:44

answered Jan 28, 2014 at 21:38

Logan Murphy

6,2403 gold badges28 silver badges44 bronze badges

Collectives™ on Stack Overflow

java program compiles with no error but does not run

4 Answers 4

6 Comments

1 Comment

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

6 Comments

1 Comment

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related