Cody Moss

Paul Clapham wrote:System.out.print(studentAry[i].toString(i));

That looks a bit odd to me. Did you really mean to use "toString(i)" there instead of "toString()"?

We are supposed to use a separate toString method to incorporate printf into the mix, I forgot to include it! Haven't written the printf yet, but the placeholder is below:


public String toString(int i) { String str=""; str = (".\t" + name+ "\t\t" + score + '\t' + grade +'\n' + '\t' + status+'\n'); return str; }

Carey Brown wrote:for (int i = 0; i < studentAry.length; i++) System.out.print(studentAry[i].toString(i));
All 50 slots of studentAry are probably not filled in, therefore, null;
Line 1: should be: i < count

Thank you so much! Worked like a charm

EDIT: but now nothing will print! Should I make a separate thread to figure out what's going on there?

Howdy all!

Working on a program that creates an array from a file, organizes it in various ways, and then prints the results. Right now I'm specifically having trouble with the printAry() method - when I try to run it, I receive a NullPointerException for the active line in printAry() (EDIT: line 102). Not sure which sections are important to this, so I will include the client class and most of the service. I'd really appreciate and help that could be provided I realize that the amount of documentation I included is not necessary, but it is required for the class.



class Lab3StudentAryService { private int count; private Lab3StudentData [] studentAry = new Lab3StudentData[50]; /* @param: none @return: none reads file and converts to array. */ public void fillAry() //constructor { Scanner scan = new Scanner(System.in); String name; int score; char grade; String status; try { File stuDataFile = new File ("filelab3.txt"); Scanner scanFile = new Scanner (stuDataFile); int count =0; while(scanFile.hasNext()&& count<50) { name = scanFile.next(); score = scanFile.nextInt(); grade = computeGrade(score); status = determineStatus(grade); Lab3StudentData studata = new Lab3StudentData(name, score, grade, status); studentAry[count] = studata; count++; } //end while }//end try catch(FileNotFoundException fnfe) { System.out.println("Invalid File name; enter again"); } //end catch } //end fillAry() /* @param: int score @return: grade Computes and returns grade based on basic letter scale. */ public char computeGrade(int score) { char grade; if (score >= 90) grade = 'A'; else if (score >= 80) grade = 'B'; else if (score >= 70) grade = 'C'; else if (score >= 60) grade = 'D'; else grade = 'F'; return grade; } //end of computeLetterGrades() /* @param: char grade @return: status Returns status of student based on letter grade. */ public String determineStatus(char grade) { String status = ""; if(grade=='A') status ="Satisfactory"; else if(grade == 'B') status ="Satisfactory"; else if(grade=='C') status="Satisfactory"; else status ="Unsasisfactory"; return status; } //end determineStatus() /* @param: none @return: return Prints info using toString */ public void printInfo() { for (int i = 0; i < studentAry.length; i++) System.out.print(studentAry[i].toString(i)); } //end printInfo()

public class Lab3Client { /* @param: none @return: none Instantiates object of service class, calls methods into use. */ public static void main (String[] args) { MyInfo.topOfPageInfo("2", "February 11, 2015"); //call topOfPageInfo Lab3StudentAryService obj = new Lab3StudentAryService(); //instantiate object obj.fillAry(); obj.printInfo(); } //end main() }//end Lab3Client

Like I said, all the code I have is posted. That's why I'm confused that it says it is defined as having three variables - I can't find anywhere in the code where I stated that.

Thanks for all the welcomes and help everyone!

I do not have a constructor - everything I have posted so far is what I've got, at this point. Do I need one? What should go in it? I have used them before, but this is my first time using arrayList.

I have tried added 'throws IOException' and removing try...catch. Now my code looks like this:

class AryListObjects { public static void addEmployee(String firstName, String lastName, double hoursWorked, double hourlyRate) throws IOException { ArrayList<GrossPayService> employees = new ArrayList<GrossPayService>(); FileReader reader = new FileReader("Proj2Part1EmployeesDataFile.txt"); Scanner in = new Scanner(reader); while (in.hasNextLine()) { firstName = in.next(); lastName = in.next(); hoursWorked = in.nextDouble(); hourlyRate = in.nextDouble(); GrossPayService objct = new GrossPayService(lastName, firstName, hourlyRate, hoursWorked); employees.add (objct); System.out.print ("\n\t\tName: \t Hours Worked: Rate of Pay: Gross Pay: "); for (GrossPayService emp : employees) //enhanced loop; note Object emp System.out.print ("\n\t" + emp); System.out.println("\n"); System.out.print ("\n\tCurrent Elements: "); for (GrossPayService emp : aryListOfObjects) //enhanced loop; note Object emp System.out.print ("\n\t" + emp); System.out.println("\n"); } }//end method }//end class

and I am receiving an error message stating that

required: String,double,double
found: String,String,double,double
reason: actual and formal argument lists differ in length

when trying to create an object.

Hello! I am currently working on a program that will read from a .txt file to create an arraylist. I will be working with the objects in the list to perform computations and display the data. The .txt file is in the following format:

lastName firstName hoursWorked hourlyRate

With no delimiters. I've messed with this thing way too much in the last 12 hours (only day off for the week ) so variable names etc have changed often. If there are errors in the program due to that I profusely apologize! Any help would be greatly appreciated.

At present the error I am receiving is "error: constructor GrossPayService in class GrossPayService cannot be applied to given types". I understand what the error means, but not how to fix it. There may be other errors as well, but at present that is all my compiler is giving me.


import java.util.*; import java.io.*; import java.text.*; class AryListObjects { public static void addEmployee(String firstName, String lastName, double hoursWorked, double hourlyRate) { ArrayList<GrossPayService> employees = new ArrayList<GrossPayService>(); try { FileReader reader = new FileReader("Proj2Part1EmployeesDataFile.txt"); Scanner in = new Scanner(reader); while (in.hasNextLine()) { firstName = in.next(); lastName = in.next(); hoursWorked = in.nextDouble(); hourlyRate = in.nextDouble(); GrossPayService objct = new GrossPayService(lastName, firstName, hourlyRate, hoursWorked); employees.add (objct); } } catch(FileNotFoundException fileNotFound) { System.err.println( "Error opening file."); System.exit(1); } System.out.print ("\n\t\tName: \t Hours Worked: Rate of Pay: Gross Pay: "); for (GrossPayService emp : employees) //enhanced loop; note Object emp System.out.print ("\n\t" + emp); System.out.println("\n");