Program Prompt For Input File / Take Its Info And Write To Report - Nullpointer Exception
Apr 17, 2014
I've got a nasty nullpointer that I have tried to resolve to no avail as of yet. The program should prompt for a listings.txt file and take its info and write to a report file. Here's the stacktrace:
run:
Input file: listings
Exception in thread "main" java.lang.NullPointerException
at java.io.Writer.<init>(Writer.java:88)
at java.io.PrintWriter.<init>(PrintWriter.java:113)
at java.io.PrintWriter.<init>(PrintWriter.java:100)
at kettask2b.PropertyListingsReport.main(PropertyListingsReport.java:34)
Java Result: 1
Some adjustments that I have attempted are:
BufferedWriter pwfo = null;
for (int i = 0; i < args.length; i++) {
String string = args[i];
pwfo = null;
[Code] ....
Here's the code:
package kettask2b;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
[Code] ....
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Apr 25, 2015
I have problem with my simple program. I tried put some text in my text area using button1 but textListener in RighButtons is always null and it's give me NullPointerException.
WriteToArea - interface
public interface WriteToArea {
public void add_a(String text);
}
BaseFrame
public class BaseFrame extends JFrame{
[Code] .....
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Mar 21, 2015
I am creating a simple ArrayList program that would enable one to input their username to it using a scanner. However, i am getting this error: "Exception in thread "main" java.lang.NullPointerException
at home.Members.addUser(Members.java:16)
at home.Main.main(Main.java:14)"
Here is the code! :
Main.java class
Java Code: import java.util.Scanner;
public class Main {
[code]....
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Apr 10, 2014
Here's a link to it : [URL] ....
The basic gist is it's "A program that reads in a text file that uses a specific input format and uses it to produce a formatted report for output."
Specifically :"For this lab you will write a Java program that produces a simple formatted report. The program will prompt the user to enter a file name. This file must contain information in a specific format (detailed below). Each "block" of the file contains information for one player in a competition -- the name of the player followed by a number of different scores that that player achieved. The program should find each player's average score, median score and best and worst scores and display them in a line on the final summary report. The program should also determine which player has the highest average score and which player has the lowest average score."
I get the following errors when I try and compile it:
Enter an input file name: Project11.txt
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException... -1
at java.util.ArrayList.elementData(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at Project11.getMedian(Project11.java:68)
at Project11.main(Project11.java:27)
I get that the error(s) reside in lines 68 and 27, among problem other areas, but I'm not exactly sure how I can fix them.
Here's my code:
import java.io.*;
import java.util.*;
public class Project11 {
public static void main(String[] args) throws IOException{
Scanner in = new Scanner(System.in);
System.out.print("Enter an input file name: ");
String input = in.nextLine();
[Code] ....
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Sep 21, 2014
I hope I'm putting this question in the right folder. I have an array of objects, and I have defined a setter for a variable in the object. When I call the setter, I get a NullPointerException. Here is the relevant code for the object.
public class Digit extends Thread {
private int digit;
public void setDigit(int digit) {
this.digit = digit;
}
// run method follows
}
Here is the portion of the main class where I define an array and then call the setter.
Digit[] digits = new Digit[10];
for (int i = 0; i < digits.length; i++) {
digits[i].setDigit(i); // NullPointerException occurs here
}
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Sep 15, 2014
If I put the highlighted text in try/catch block it is throwing NullPointerException , if I am using command line arguments then also it is showing the same exception.
public static void main(String []args)
args = null;
args[0] = "test";
System.out.println(args[0]);
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Dec 2, 2014
I have the following unit test that gives me a null pointer exception. The debugger goes to the finally block right after the line that creates a connection factory. Here's the test:
@Test
public void receiveMessage() throws Exception {
MessageConsumer consumer = null;
ConnectionFactory connectionFactory = null;
Connection connection = null;
Session session = null;
Destination destination = null;
[code]....
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May 8, 2014
I am getting a nullpointer exception after "cleaning" up my code by putting repetitive stuff in a method.
The error points to this: ai.getItRight(n, answer);//make sure the user enters yes or no..
The error occurs at lines 19 and 25.Here is the relative code:
public boolean AskQuestions(Node n, String yesOrNo, String answer, String question){
if(yesOrNo.equalsIgnoreCase("no") && n.getRight() == null){//i guessed the wrong answer
System.out.println("I give up. Who is it: ");
answer = input.nextLine();
[code]....
My previous code, which use to have the contents of getItRight in place of lines 19 and 25 worked just fine. So why am I getting this error? I dont want my methods to be crazy big like how they usually end up.
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Jan 8, 2014
I would like to know how to write Java lab report. If you have links or sample.
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Aug 14, 2014
I've been closely following a tutorial series, and as far as I can tell my code is exactly the same, but not functioning.
The app throws a nullpointer exception here on "controller.saveToFile(fileChooser.getSelectedFile ());"
// Export data item
exportDataItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (fileChooser.showSaveDialog(MainFrame.this) == JFileChooser.APPROVE_OPTION) {
try {
controller.saveToFile(fileChooser.getSelectedFile());
[Code] ....
There are no errors popping up in the code, and I dont understand why there is a null pointer exception when Im saving this file.
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Feb 21, 2015
Design, write a java program to input 7 integers and, for each integer, calculate and display its square and cube.
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Feb 11, 2015
I am trying to read contents from a file and display them to the user. However, when I enter the file into the program I get the following error: "exception in thread 'main' java.util.MismatchException. What am i doing wrong?
import java.util.Scanner;
import java.io.*;
public class Project1{
public static void main(String[] args) throws FileNotFoundException {
double balance;
double item1Price;
[code]....
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Mar 24, 2014
a. Assume that we have a list of employees' names of a company and their ages. Write a program that reads from the user several lines of input. Each line includes an employee's name and his/her age (as an integer). The program should calculate and print the following:
- The average age of all employees (rounded to 2 decimal places).
- The oldest employee and his/her age.
Hints:
You could assume that the user will insert valid data and at least one employee.
You could assume that the oldest employee is only one person.
User could stop the program via entering the word "end" as an employee's name.
Sample Input and Output: In each line, insert an employee's name and his/her age To halt the program, insert "end" as an employee's name
Adam 30
Tom 41
Ted 45
Karl 30
end
The average age of all employees is 36.50.The oldest employee is Hisham whose age is 45
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Aug 1, 2011
Write a Java program that reads a positive, non-zero integer as input and checks if the integer is deficient, perfect, or abundant.
A positive, non-zero integer, N, is said to be perfect if the sum of its positive proper divisors (i.e., the positive integers, other than N itself, that divide N exactly) is equal to the number itself. If this sum is less than N, the number is said to be deficient. If the sum is greater than N, the number is said to be abundant.For example, the number 6 is perfect, since 6 = 1 + 2 + 3, the number 8 is deficient, since 8 > 1 + 2 + 4, while the number 12 is abundant, since 12 < 1 + 2 + 3 + 4 + 6.
SAMPLE OUTPUT:
1.)Input N: 5
5 is deficient.
2.)Input N: 6
6 is perfect.
3.)Input N: 18
18 is abundant.
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Apr 22, 2015
Write a program that asks the user to enter five test scores. The program should display a letter grade for each score and the average test score. Write the following methods in the program:
calculateAverage This method should accept five test scores as arguments and return the average of the scores. determineGrade This method should accept a test score as an argument and return a letter grade for the score, based on the following grading scale
Score Letter Grade
90-100 A
80-89 B
70-79 C
60-69 D
Below 60 F
double test1,test2,test3,test4,test5;
double average;
char grade;
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter the first score");
test1 = keyboard.nextDouble();
System.out.println("Enter the second score");
test2 = keyboard.nextDouble();
[code]....
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Feb 15, 2015
I want to write a java program which displays to get the GPA of a student as a keyboard input. Then display the class of the degree according to the following criteria using a switch-case statement (if-else statements cannot be used). If the user insert an invalid gpa you should display a message Invalid GPA.
gpa ≥ 3.50 First Class Hons
3.49 ≥ gpa ≥ 3.00 Upper Second Class Hons
2.99 ≥ gpa ≥ 2.50 Lower Second Class Hons
2.49 ≥ gpa ≥ 2.00 Pass
2.00 ≥ gpa Fail
Here is my code:
import java.io.*;
public class q7
{
public static void main(String[] args)
{
InputStreamReader ISR=new InputStreamReader(System.in);
BufferedReader BR=new BufferedReader(ISR);
[code]...
.But when I use Command console to run this it says: 1111.jpg. I also wanna know is there another way to do this with switch- case statements.
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Dec 8, 2014
I need to write a program where the user inputs name, age, email, and cell and write the user inputs to a text file. I need to have it so the file can be added to if more than one set of information is added. Currently, every time I click the button, the file is overwritten instead of added to. How do I correct this? Current code is as follows:
try
{
FileWriter writer = new FileWriter("ContactInformation.txt");
BufferedWriter bw = new BufferedWriter(writer);
nameTextField.write(bw);
bw.newLine();
ageTextField.write(bw);
bw.newLine();
emailTextField.write(bw);
bw.newLine();
cellTextField.write(bw);
bw.newLine();
bw.close();
nameTextField.setText("");
ageTextField.setText("");
emailTextField.setText("");
cellTextField.setText("");
nameTextField.requestFocus();
}
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Jan 9, 2015
1.Write a JAVA program that will input 10 scores and output the Highest and Lowest score.
2.Write a JAVA program that will input the base and power and display the result: Example: Base is 4 Power is 2 the answer is 16 (Note: Math.pow( ) method is not allowed)
3.Write a JAVA program that will input an integer number, and then will output the sum of all inputted numbers. The program will stop in accepting inputs if the user entered 0.
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Dec 2, 2014
I am trying to learn how to use file input/output in addition to exception handling... The problem is my textbook wrote this chapter for a version of Java that hasn't come out yet, so everything I do "according to the textbook" doesn't work. any feedback on correcting these exception errors because I am not sure what is causing them or how to fix them.
I was able to have it display the name of the book in the Book.txt file, but when I added the second part if the file doesn't exist, that's when the errors came up and it wouldn't compile.
import java.io.*;
import java.util.*;
public class DisplayBook
{
public static void main(String[] args) {
try {
File book = new File("Book.txt");
FileInputStream in = new FileInputStream(book);
[Code]...
These are the compilation error messages I am receiving: (I have managed to get it down from 7 errors to just 4, but now I'm stuck)
DisplayBook.java:15: error: unreported exception IOException; must be caught or declared to be thrown
while ((letter = in.read()) != -1) //if file exists, displays book title
^
DisplayBook.java:24: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
[Code] ....
4 errors
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Dec 17, 2014
My program is user input 20 char and the program will print the most common. So I use another int arr which count the number appears in the original array. i know its not so Effective but I don't know why it run but it stop in the middle. I got this code :
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 20
at Ex2.common(Ex2.java:39)
at Ex2.main(Ex2.java:23)
import java.util.Scanner;
class Ex2 {
public static void main(String[] arg) {
Scanner reader = new Scanner (System.in);
char[] arr=new char[20];
System.out.println("Please enter 20 chars:");
for (int i=0;i<20;i++)
[Code] ....
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Jul 14, 2014
So I was going to try to create a program that prompts input and creates a file (That didn't exist before) with that input as name.Then, the program prompts inputs after stating questions such as 1 + 1, then if the user inputs an answer, put "Question # = Correct "or" Wrong.Code SO Far:
Java Code:
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
public class File_Read {
public File_Read() {//File_Read is the Interactive object
[code]....
So that it puts the Correct or Wrong into the file.
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May 10, 2014
I was wondering where can I find info on how to grab info from websites to use in a program?
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Mar 19, 2014
My program successfully reads a file, reports back what it finds and creates an output file. However, I cannot get it to write to the output file, it is always blank!
Here's my code:
import java.util.Scanner;
import java.io.*;
public class Ex19
{
public static void main (String [] args)
{
//Variables
[code]....
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Oct 17, 2014
I'm rather new to programming and I'm trying to make a gui program that will allow the user to create text files. They will be prompted to enter what they'd like to save their file as and then they will be allowed to input text to that file . They will also be allowed to open their files to modify or view its contents. So to start things off, I'm making a prototype if you will.. I've been able to save to a file the problem occurs when I try to read/display it.
Main Class:
public class MainActivity {
public static void main(String[] args) {
// Access to other classes
WriteFile writer = new WriteFile();
ReadFile reader = new ReadFile();
[Code] ....
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Jul 10, 2007
I want to create and write to a excel file from a java program. I found a tutorial online and wrote a java file as under:
Java Code: import java.io.File;
import java.util.Date;
import jxl.*;
import jxl.write.*;
public class jExcel{
WriteableWorkbok workbook = Workbok.createWorkbook(new File("output.xls"));
public static void main(String args[]){
WriteableSheet sheet = workbook.createSheet("First Sheett",0);
Label label = new Label(0,2,"A label record");
sheet.addCell(label);
[code].....
But when I compile this file, I get errors telling that package jxl does not exists and so on. Do I need to download it ?
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Mar 30, 2015
i am trying to write a program in which the user will select a text file(which contains information that the graphical output will be based). I have successfully set up my file chooser however when i select the text file,i do not get any graphical out put. please see attached .zip file for code.
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