Thread: Problem extracting data from file

List<Object> variable = ArrayList<Object>();
Scanner fileScan;
File inputFile = null;

I checked my inputFile to see if it was in the directory. If yes then the code continues below.

try {

fileScan = new Scanner(inputFile);

//scans the datafile and adds the data to the ArrayList
while (fileScan.hasNext()) {

String callType = fileScan.next();

//DEBUG CODE
System.out.println("Calltype: " + callType);

if (callType == "D" || callType == "L") {

// more code

Here's an example of a line of data I am reading. The times are imported as strings, tested for validity, then I create an object from it in HH:MM:SS. The two time objects are then used to create a total time object.

D 08:00:00 09:00:00

The problem is that when I am trying to read the first letter for D or L the whole data file is read in. I want to be able to read and separate between the "D" or "L" and the two times.

okay, I fixed that to look like this "if (callType.equals("D") || callType.equals("L")) {"
, but now it's creating a new error below and I am still am having the issue with extracting the strings in the line of data one at a time. The change to the code to .equals() created a NullPointerException in my abstract class. in my toString() method below. This method is also an overridden class in my original object class above.

public abstract class MyAbstract {

public String toString() {

String costOutput = "";

String startTimeOutput = startTime.toString(startTime); //send PreciseTime objects to 'toString()'
String endTimeOutput = endTime.toString(endTime);

costOutput += this.computeCost();

return startTimeOutput + "\t"
+ endTimeOutput + "\t"
+ costOutput;
} // End toString() method

public abstract double computeCost();

} //end MyAbstract class

The startTime and endTime are objects created by another class CheckedTime which extends one class, which itself extends to a third class. The third class would be considered the first class (original parent) in line as I progress from class to class creating objects. It's a pretty complex class project as projects go.

here's the error message, but it refers to probable problems in some of my other classes when some of my objects are created. All of my files compile, but I get this runtime error.
Exception in thread "main" java.lang.NullPointerException
at LocalCall.toString(LocalCall.java:58)
at java.lang.String.valueOf(String.java:2826)
at java.lang.StringBuilder.append(StringBuilder.java: 115)
at java.util.AbstractCollection.toString(AbstractColl ection.java:422)
at java.lang.String.valueOf(String.java:2826)
at java.lang.StringBuilder.append(StringBuilder.java: 115)
at MonthlyPhoneBill.main(MonthlyPhoneBill.java:119)

I'm guessing the problem is either something you did in the toString() of LocalCall that's not being met or you passed it a wrong parameter or something in your main method of MonthlyPhoneBill.

Please post LocalCall and MonthlyPhoneBill classes.

not sure why I had my List<Object> that way. I do have "new" before my ArrayList<OBject>. As for the file name, that's above the code I originally listed in this thread. Here's the code that is above the try-block above.

do {
System.out.print("\nEnter file name to read: ");

try {

fileName = stdin.nextLine();
inputFile = new File(fileName);
}

catch (Exception ex) {

System.out.println("File does not exist.");
}

} while (!inputFile.exists());

I see that Junky, but that's the issue that I can't figure out. I have toString() in my abstract class and my LocalCall class and another similar class LongDistanceCall. I'm having trouble tracking which instance variables are being used and which toString() is being used. I've tried deleting the body of my toString() in my PhoneCall abstract class, but that fails. I think it's in how I'm using and accessing my instance variables to be honest. To get to LocalCall, the final step as the data traverses the classes.

Initially I create a Time object of which the variables hours and minutes are derived from a Time class. In my second class in the hierarchy PreciseTime extends Time, the instance variables of Precise time access the super(hours, minutes) from Time and add seconds, to instantiate a PreciseTime object. The next level is CheckedTime which also extends PreciseTime. CheckedTime does some error checking and it uses super(hours, minutes, seconds) to instantiate a CheckedTime object using the super instance variables.

I'm still getting nullpointer exceptions in my LocalCall class and don't know why. Does it have something to do with my abstract class or from the objects created by my MonthlyPhoneBill class. I'm stuck and can't find the problem.

Every time you post source code to a java programming forum that has been changed since you posted your Exception stack trace, a Java pony dies. Post the Exception output from the version of the source that you've just posted.

Yes sir, LocalCall extends the abstract class PhoneCall, but I have a toString() method in both of them.

Will try that tomorrow. I have my final to sleep for my final, then will be back to finalize my project for Saturday. I appreciate the help.

I've added print statements throughout and can see what's causing the problem, but can't determine why. The problem is that I get the NullPointerException on line 40 of this code. Here is line 40:

40 callLength = endTime.toSeconds() - startTime.toSeconds();

I think the problem is that use of the call to super variables is causing the problem because they may not have access variables which are actually instances of CheckedTime. The variables in the constructor startTime and endTime are objects created by CheckedTime. CheckedTime objects are created with this constructor CheckedTime(int, int, int). I think my NullPointer Exception is trying to access object instances that aren't there. Any ideas how to get access to the checkedTime objects. The objects are actually instantiated in my main.

///My Class
public class LocalCall extends PhoneCall {

//Class variables
CheckedTime startTime;
CheckedTime endTime;
private double totalCallLength;
private double totalCost;

//Constants
static final double LOCAL_COST = .01;
static final int HUNDMIN_to_SEC = 6000;

//LocalCall constructor
public LocalCall(CheckedTime startTime, CheckedTime endTime) {

super(startTime, endTime);

} //end constructor

public double computeCost() {

double callCost = 0;
int callLength = 0;

callLength = endTime.toSeconds() - startTime.toSeconds();
totalCallLength += callLength;

if (totalCallLength > HUNDMIN_to_SEC) {
callCost = callLength * LOCAL_COST; //Calculate call cost
}
else {
totalCost += callCost;
}

return callCost;

} // End computeCost() method