NullPointer Exception From Calling A Setter In Array Of Objects
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
}
I have a PrimeFaces page with a calendar component on it. Radio buttons on that page work fine and call the setter method on the back end. The Calendar however doesn't call the setter. The getter method is called on page display.I'm using the PrimeFaces v 5.0 jar file.
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 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{
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.
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:
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.
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;
I know that I am not 100% comprehending try/catch blocks, but after scouring message boards, forums, and Oracle, I still can't pick out where I am going wrong.
I have a ValidateInput class where I am trying to check that a String only has letters. If not, then throw an exception message via JOptionPane. I created my own NonLetterException class. When I call the method containing the try/catch Eclipse gives me an Unhandled Exception Type error.
in main() ValidateInput validate = new ValidateInput(); String name = "error"; for(int x = 0; x < 1;){ name = JOptionPane.showInputDialog("Welcome. What is your name?"); boolean isItName = validate.stringInput(name); //error appears at validate.stringInput if(isItName)
[code]....
Aren't I handling it in the try/catch? What did I miss?
Also, I have have tried the NonLetterException class as nested in ValidatedInput, but also not nested. To me nested makes more sense. I have never nested classes before, but it makes sense to me because I am not using this exception in other parts of my program.
I have a file greenGrow.txt, and every three lines of the file has a last name, first name, and yard size. Every time a Customer object is created, I need to read the file 3 lines and assign the object a last name, first name, and yard size.
Snippet of my code:
import java.io.*; import java.util.*; public class Customer { private String lastName; private String firstName; private int yardSize;
[Code] .....
My issue is that I cannot call readFile() from the constructor, and I'm assuming that's because I throw Exception on readFile(). Is this a simple fix, or am I looking at it the wrong way?
I have two classes, MonsterGame (shown below) and Monster. Monster has a public accessor method to get it's private character variable, which represents the first character of the name of the Monster in question.
I'm just a bit confused as to why am I unable to cycle through the array of Monsters I have in the MonsterGame class and call
m.getCharacter(); (pretty much the last line of code) public class MonsterGame{
private static final char EMPTY_SQUARE = ' '; private char[][] gameBoard = new char[10][10]; private Monster[] monsters = new Monster[4]; private int maxXBoardSize = gameBoard.length -1; private int maxYBoardSize = gameBoard[0].length -1;
[Code] ....
I understand that there need to be instances of objects to call methods, but is that not the case here? the Monster objects are have already been created, no? Do I need to create an index for the array? is the for loop not enough?
I want to write classes with methods that perform JDBC operations that throw SQL exceptions. For many of the methods, I'd ideally like to be able to have them catch exceptions and just send them to a standard Logging system "IF" the code that calls the methods is not going to catch the same exception. However, I'd like the "option" to have code that calls these methods catch the same errors if I want to but not "Require" the calling routines to catch them.... so I don't want to declare the methods with a "throws" that would require all calling code to Try/catch.
For some background, the logic behind what I'm looking to do is that there will be lots of places where these classes and their methods may be used where the code is basically "throw away" scripting code where just having error logs generated is more than sufficient. However there are also places I want to use the same classes/methods that I would want to handle the exception differently. So, for at least half the places I want to use these methods, there's no good reason to require cluttering the calling code with Try/catch, but when I DO want to handle the exceptions, I'd like them to get passed up to the calling routine so I can handle them in a way that is appropriate for the calling routine. Does that make sense?
I guess I'm kind of looking for is the ability to "override" the catch of a called method "IF" I want to but to treat the method as though it doesn't throw any exception "IF" I don't want to override the called routines catch logic.
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.*;
Say I have two classes, Author and Book, and I have 2 author objects and 10 book objects. I would like to know how to do two things:
1) Make some sort of connection that makes clear that author X wrote books A, B and F. 2) Call a method from a book object that is connected to an author.
Seeing as I don't know which books will be connected to an author, is there some way to call a method of an object bases on a variable object name? Something like call the getFirstPage() method for every book that is linked to author X?
So I need to generate 10 random integers in the range 1-20 but i have to store them in an array called numbers. Then I have to call a method called displayArray which displays the contents of the array and for the assignment i have to use a for loop to traverse the array. The method header for the displayArray method is:
public static void displayArray(int[] array)
This is what I have done
public class RandomIntegers { static int numbers = 0; public static void displayArray(int[] array) { System.out.println(numbers + "Numbers Generated");
I am receiving an ArrayIndexOutOfBoundsException for the following code, which moves a creature through a 2D array maze. I have altered the clauses of the first if statement for the four direct methods (north, south, east, and west) multiple times (i.e. x + 1 >= 0 && x > 0 && x - 1 > 0 && x < array.length...etc). However, while the code occasionally runs, more often than that it returns this exception. Catching the exception seems like a poor workaround though if worst comes to worst I'll do that.
I included only the relevant functions of the code:
public boolean goNorth(char[][] array) { boolean success = true;; x = getX(); //x = this.x; y = getY(); //y = this.y; if ((x - 1 >= 0 && x - 1 < array.length) && (y >= 0 && y < array[x].length)) {
So I just finished up my term project and have everything working but I wanted to make one slight adjustment to the code and Im not exactly sure what I'm doing wrong - it involves retrieving a set element from an array from a different class so to some what show what I have going on:
public class example1 { private example2 Examp; public example1() { Examp = new example2(); } public void getArray() { if(Var >= 10 && Var <= 20) {
[Code] ....
I have an if statement that looks at a sum of numbers, and predetermined upon the set of numbers I want it to output a message by calling the index number in the array and returning the string. I currently just have the message in the if statements but would be nicer to just pull them from a different class to keep it consolidated.
In this project each individual will create a data analysis program that will at a minimum,
1) read data in from a text file, 2) sort data in some way, 3) search the data in some way, 4) perform at least three mathematical manipulations of the data, 5) display results of the data analysis in numeric/textual form, and 6) display graphs of the data. In addition, 7) your program should handle invalid input appropriately and 8) your program should use some "new" feature that you have not been taught explicitly in class.
(Note: this is to give you practice learning new material on your own - a critical skill of today's programmer.) If you do not have a specific plan in mind for your project, below is a specific project that meets all of the qualifications as long as 7) and 8) are addressed in the implementation.
Everything is done except I need to call my methods in my GradeTester.
GradeBook:
/** *This class creates an array called scores. *This class determines the length of the array scores and determines the last grade in the array scores. *This class sorts the array using a bubble sort, and searches the array. *This class calculates the mean, standard deviation, and the median of the grades in the array scores. *Once the grades in the array is sorted, the class then calculates the highest and lowest grades in the array. */
public class GradeBook { public final int MAXARRAY_SZ = 20; double [] scores = new double [MAXARRAY_SZ]; int lastGrade = 0; double mean = 0;
I am trying to set my setter and getter various times o that I can store a name, price and value but i can only set it once. Once i try to set again the previous entry resets.I have tried
This sets the values for me and i receive the input i entered but if i try to enter again the input from before is removed.I have searched array lists and tried
[code] List<Object> list new ArrayList<Object>(); list.add(jobname) list.add(price) list.add(Event)
out.println(list.get(0));
for (Object s : list) { out.println(s); }
For this to work I would have to keep adding list.add. Is there a way I can use the array to add a new item to the list so that when I try to display what I have stored in the setter and getter it will display what I have entered in each time instead of only the last input? or any other way that may be possible to do this?
i'm trying to modify and use a GUI to set the variables the setter methods. while the code seems valid to me and should work perfectly, i get ArrayIndexOutOfBounds and StringIndexOutOfBounds and respectively lines 111 and 134. i'm am not the original author of this code, all i want is to get it to work fine.
Exercise the Coin class using a driver class in which 5 coins are flipped, as a group, 1024 times. Display the number of times exactly 4 tails are obtained. Display the number of times exactly 5 tails are obtained. Use an array of Coin.
how to put an object into an array?I know how to make a coin class with a Heads and Tails, but I dont know how to make 5 coins all at once.
i need to change my code in order to stop the member variables from being directly altered and its been suggested that i should use a setter and getter method. Ive read up about these and im still unsure at how they should be implemented into my code for my project.
I have been assigned with a task to have a class which has the methods setImage and getImage. These methods are meant to set the ImageIcon by using the url taken from another class and the getImage method is meant to return the ImageIcon that was set before hand. The problem is that i'm not really familiar with ImageIcon so the code in both my methods is giving out errors and i just can't figure out why. Heres the code in the class that has the setImage and getImage methods:
public class Die implements DieInterface { private ImageIcon [] image = new ImageIcon[6]; //the number of images that would be stored in this array is 6 (six faces of the dice) ublic Die() { //This puts images into the images array(the different die faces) image = new ImageIcon[6];
[code]....
And this is where i call the methods (set and get methods) in the other class:
A blood clinic has hired a team of software developers to build a custom application to track patients. The clinic needs to keep a record of each patient and his or her blood data. Ultimately, they want all of the information stored in a database. As a starting point, the development team leader informs the team that the application has to have a set of core classes that represent the “real-world” entities the program needs to deal with. As a developer on the team, your job is to build a Patient class along with a BloodData class so that each Patient contains a BloodData object. This principle is known as “composition.”
Building the Framework Begin by creating a public Java class named PatientBuilder that contains a main method. Then, in the same file, create a non-public class named Patient and another named BloodType. Save the file as PatientBuilder.java. Note: If this was a real development project, you would put each class into it’s own file and put the files in the same folder. By combining them all into one file, we avoid having to submit three separate files, making it easier to keep all your work in one place.The BloodData Class This class should hold all of the attributes to hold the data the clinic needs for a given patient’s blood. Implement the following capabilities to accomplish this objective:
• Create a field to hold a blood type. The four possible blood types are O, A,B, and AB. For this project, you can simply define the field as a String. • Create a field to hold the Rh factor. The two possible Rh factors are + and –.For this project, you can simply define the field as a String. • Create getter and setter methods for both fields. • Create a default constructor that sets the fields to “O” and “+” • Create an overloaded constructor that accepts two parameters – one for a proposed blood type, and another for a proposed Rh. The constructor should call the set methods and pass these parameter variables in to them.The Patient Class This class should hold all of the attributes to hold the data the clinic needs for a given patient’s blood. Implement the following capabilities to accomplish this objective: • Create a field to hold an ID number along with get and set methods. • Create a field to hold the patient’s age along with get and set methods. • Create a field to hold the BloodData for a Patient. When declaring the field, initialize it by instantiating a BloodData object. Create get and set methods. • Create a default constructor that sets the ID to “0”, age to 0, blood type of the BloodData object to “O”, and Rh value of the BloodData object to “+”. • Create an overloaded constructor that accepts the following parameters: ID,age, blood type, and Rh. The constructor should call the set methods for the field associated with each parameter.The PatientBuilder Class.This class should contain the main method from which the program runs. In that method, implement the following functionality:• Ask the user for the ID, age, blood type, and Rh factor of a Patient. • Create a Patient object, passing all of the data obtained from the user into the object. • Write the code necessary to display the ID, age, blood type, and Rh factor of the Patient by calling the appropriate get methods of the object.
MY CODE ( which does not compile since it is wrong...)
import java.util.Scanner; public class PatientBuilder { public static void main(String[] args){ String patientID; int patientAge; String patientRh; String patientBlood;
