I use the BlueJ software to develop my programs. I am creating a program which holds two data structures; Array List and Binary Tree. I have created a person class which is used to declare variables containing people, this class also contains a method which prompts the user to input 3 characters of a memorable word. These people are created within the array list and binary tree. This actually works in practice, within the program, but i get an error, and i need the program to contain no errors.
In my binary tree class, i want to call this method.I have attached 4 images to this post, an overview of the classes used, a look at highlighted code which is an attempt at calling a method from the person class, and the method contained within the person class itself. Note that the person class is just called "Person". The 4th image is the error being displayed.
having trouble trying to understand the insertion and removal of Nodes.
I have to insert a new node at the end of the linked nodes, if i insert by terminal : 1, 2, 3. The printed nodes are going to be in the same order, 1,2, 3.
I have done the exercise, but it only prints the last node created and i dont know where its the problem. We did it before with "insert at the beginning", may be the problem is with the print() method in SimpleList.java, but i dont know how to print "backwards".
This is the code:
Node.java
public class Node { public int infoNodo; public Node next; } SimpleList.java public class SimpleList { private Node head;
I am making a basic calculator using SWING.I want my JTextField to stretch across the top, above my buttons. All I can seem to get is it be the same size as one of my buttons.
I'm suppose to be doing a factorial of a number within certain constraints (say a number between 5 and 10). I get the factorial easy enough but I'm getting it for every number no matter what I put in.
textio is used instead of scanner for our class.
Java Code:
public class Factorial { public static void main(String[] args) { int max = 0; int x = 0; long y = 0;
[Code] .....
Ideally I should be able to put in a number outside the range and the program will do nothing until I put a number in with the correct value.
I know that Servlets are meant to do the JDBC tasks, JSP are only for displaying the final information forwarded by the Servlet.
JSP are Servlets too, but I heard an idea that it is safer to make database operations in a Servlet.
The idea is that I have a few JSP that use JSTL tags to retrieve some database information. By doing this I was concerned that this may be bad design, though I really wanted to get in fit with the JSTL tags.
Are there any security weaknesses if doing some JDBC stuff in a JSP, by using JSTL or plain Java code in <%...%>?
P.S. In my JSP I only retrieve data, not modifying it.
I have been doing a program that allows the user to input students names and numerical grade values. I have already completed 3/4 of the program but am stuck on the bubblesort method as this is what it requires:
The program must have an indefinite loop, which prompts the user to select a sorting criterion or to end the program, and must also use bubble sort. Note: The user may either select name or grade as the sorting criteria. The program must use bubble sort to sort that data according to the specific criteria and then use another loop to display the data. This process must continue until the user ends the program.
My problem is, while i can easily do the bubblesort, where to look on how to link elements of the two arraylists I'm using (one for grades, one for names) so that when the user decides what sort they want, the individual's name and grade stays together.
I have started coding recently and been working on a simple java timer. My problem is that the button does not show any response even though an action has been done via actionlistener.
Example: When I press the "Start Timing" button, it should start timing and output the counter to Static Timer but instead of doing that, it does nothing.
The important bits are under Timer code and Button Start Timing. Is their something that I'm missing?
//--- All imports have been handled --- public class GUI { double counter = 1; double inputA = 1; int delay = 1000; Timer timer = new Timer(delay, null);
The following code uses a column constraint to specify that a column of labels should extend horizontally in their cell but they don't as you can see by looking at their border. My mistake or a bug?
I have two codes of needed to run but after processing, the said above error is preventing it from getting the general output of the code.I can't seem to find my errors or I don't have any clue at all, if perhaps you know, here's the codes:
Error : PHP Code:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at simpleOutput.main(simpleOutput.java:13) public class simpleOutput { public static void main(String args[]){ int n = Integer.parseInt(args[0]); for(int i = 1; i <= n; i++){ } for(int i = 1; n <= i; n++){ System.out.print((i*n)+" ");
I'm trying to call the grade.processFile method from the main method but I'm getting this Error below. I'll post my code which includes the main method and the class underneath the error message:
Exception in thread "main" java.lang.NullPointerException at java.io.FileInputStream.<init>(FileInputStream.jav a:130) at java.util.Scanner.<init>(Scanner.java:611) at MyGrades.processFile(MyGrades.java:49) at myGradesMain.main(myGradesMain.java:19) import java.util.Scanner; import java.io.*;
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 {
I'm trying to have the program create a .txt file for me but it is not working properly. It just keeps printing the exception error "The file could not be found" and exits the program.
// This program asks the user for input for a name, phone number and notes up to 200 entries. // It stores every contact in a file. Type 'h' for help while running this program.
import java.util.Scanner; import java.io.*; public class Phonebook { static Entry[] entryList = new Entry[200]; static int numEntries; public static void main(String[] args) {
[Code] ....
After running the code, I go into my workspace folder and I see that the file was created. What to do because running the program will always print "could not find the file".
I have an input text file as file.txt where, it consists of only real values separated with commas, and arranged as rows as columns as mentioned below :
the number of rows is 100 and the number of columns are 9, that is they are fixed.Above is just an example, the file consists of decimal values.What I require is for each column of values I need to find out it's average or mean, that is in above example,
for 1st column:(1+1+2)/3 for 2nd column(2+4+4)/3 for 3rd column(3+7+5)/3,,,,,,,like this till the last column.
So I need to take the input from the .txt file, calculate the column average of each column and the average of each column must be displayed as output. I have done a bit of coding, but it is giving a run-time error as NullPointerException.I will forward my code as attachment, the reading of file, is done as string in java and then it must be converted to double values, also to read the comma separated input from a file I have used the split().
I am trying to make a Applet and it works fine in Eclipse, but when I use it on the webserver I only obtain this Exception. It only happen when I make calls like this:
I wrote a program that would play a game of Hangman. It plays the game but it keeps on bringing up a exception error. This is my class code
import java.util.ArrayList; class Assignment2Q4 { private final ArrayList<Character> guessList = new ArrayList<>(); private final char[] charArray; private final String secretWord; private int guesses;
[Code] ....
This is the output that is given:
Enter the secret word: pizza Guess a letter: d ????? Guess a letter:
[Code] .....
Also when I guess the first letter of the word correctly it stops the program without going further on with the guessing.
Exception in thread "main" java.lang.NullPointerExceptionat DogTestDrive.main(DogTestDrive.java:19)
Here is the source
class Dog { int size; String name; void bark () { if (size < 60) { System.out.println("Woof woof");
[code]....
Some background: I'm reading "Head first Java 2nd edition" and I'm going through the examples which is showing me how to change the state of an object. The original code looks like the code below, however the previous chapter went over creating array's of an object, so I created an array of the object "Dog" and wanted to re-write it this way. To my understanding, it should work but it's giving me that error when I execute it. The error itself isn't very clear, if I could get a line number pointed to, that would work.
class Dog { int size; String name; void bark() { if (size > 60) { System.out.println(“Wooof! Wooof!”); } else if (size > 14) { System.out.println(“Ruff! Ruff!”); } else { System.out.println(“Yip! Yip!”);
For this program, I have to run a slot machine. It runs until right before the do while loop and then I receive the error: Exception in thread "main" java.util.InputMismatch.Exception. Searching around, someone said it was a scanner error and adding a call keyboard.nextLine(); fixes the problem- however with that I receive the same error.
Code : import java.util.Scanner; import java.util.Random; import java.io.*; public class SlotMachineSimulation { public static void main(String[] args) throws IOException { int number;
I am working on a magic square program. My program compiles. However, when I enter the square dimension it does not select the correct file. The error says "java.io.FileNotFoundException." It looks like it inserts 0 instead of the entered dimension.
import java.util.*; import java.io.*; public class Trial2 { public static int size, row, col; public static void main(String[]args)throws java.io.IOException
Question 1: I am working on an assignment where I have to remove an item from a String array (see code below). When I try to remove an item after entering it I get the following error "java.lang.NullPointerException." I am not sure how to correct this error.
Question 2: In addition, I am having trouble figuring out how to count the number of occurrences of each string in the array and print the counts. I've been looking at other posts but they are more advanced and I have not yet learned how to use some of the tools they are referring to.
private void removeFlower(String flowerPack[]) { // TODO: Remove a flower that is specified by the user Scanner input=new Scanner(System.in); System.out.println(); System.out.println("Please enter the name of the flower you would like to remove:
I am very much new to jsp and servlet. I want to set global error page for every exception occured at server side. I am trying with following code , but something is going wrong and I am not able to c error page.
I have studied about the hierarchy of exception classes in which Throwable class comes at the top and two of its direct subclasses are Error and Exception..I just want to ask if in some code snippet we throw an instance of Error or its subclass within the try catch block then will that be also called "exception handling" ? I am asking this because Error class is not a child class of Exception therefore cant be said an Exception, therefore handling the same should not be called exception handling
I was giving a quick skim to some tutorials on the internet where I have found the exception that is handled is also declared in the throws clause of the method wrapping the try-catch block. For a code representation consider the following:
public void methodName() throws IOException { try { ... } catch (IOException ex) { .... TODO handle exception }
