How To Change State Of Object - Main Method Exception Error
Jan 8, 2015
The error I get when I execute my java file.
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!”);
Caused by: javax.persistence.NonUniqueResultException: result returns more than one elements at org.hibernate.ejb.QueryImpl.getSingleResult(QueryI mpl.java:109)
What are the common reasons for the above exception and the suitable fixes?
I am working on a program that will allow a user to input grades for a class of four students who have taken two tests. Based on the grades entered, the program will calculate the averages of the two tests for each student and display it along with their respected letter grades.
Now I can get the program to compile successfully, but after inputting the grades in, I get the error message saying that it cannot format given object as a number. I am using 4 arrays to execute this program and maybe that's why I'm having the trouble? I'm not sure because I am still fairly new at this stuff and can't sen to resolve it.
I was having problems for a while and then finally got excited when I got it to compile without any errors and now I'm getting an error inside my program. All I need to do is format the numbers of the grades into something like: 000, and each of the averages as 000.0. I understand how to do it because I have done it in another program I've done in the past. I just don't know how to fix this error that is coming up.
here is my code:
import java.util.Scanner; import java.text.DecimalFormat; public class TestAverage { /** * A program that will store and process 2 test scores for a class of 4 students. * The program will prompt for the test scores as shown above in the sample run. * After all the data is entered,the program will display the score for test 1, test 2 . * The average of the 2 tests and the letter grade for the class for each student in a tabular format. * *
When I try to call an object it can't find the symbol in the argument list. NetBeans says that it cannot find the movieCategory symbol when I try to call it. When I compile it to test a popup comes up that states "One or more projects were compiled with errors. Application you are running may end unexpectedly. I ran it anyways and everything runs up to the point of where it should call the object.
At this point it should get the Movie object and run the code within that, but if I put one of the categories it throws. "Exception in thread "main" java. lang.RuntimeException: Uncompilable source code - Erroneous tree type: <any>at MovieApp.main(MovieApp.java:33)Java Result: 1"
From my understanding to call an object it requires objectName.methodName(argumentList). Here is my Main method
/** *This application will store a list of 100 movies and display them by category */ import java.util.Scanner; public class MovieApp { public static void main(String args[]) { //Displays <code>String</code> welcome message System.out.println("Welcome to the Movie Application."); System.out.println("There are 100 movies in the list."); System.out.println("What category are you interested in?"); System.out.println();
I've been writing classes over and over for school. So I create a class outside of my main class. I create a new constructor and then create objects from my main class. I hope that makes sense. So i use methods in that class to work with the object. So I have an object name I've created <dot> method name. So I can create objects and then use methods from the class, but I'm wondering can I create a method in my main class and use it on that object? I don't understand how to do that.
I am writing a palindrome program. I don't understand what is wrong with my Main method. It is giving me error and error is "Can not find symbol in main method"
import java.awt.*; import java.awt.event.*; import javax.swing.*; public class PalindromeA extends JFrame { private JTextField inText; private JTextField outText;
I am attempting to create a very simple game where two squares move around and each can see the other square moving. This is a multi-player game over a TCP network using JavaFX. I am getting an illegal state exception when I call requestFocus(). This is my server:
public class GameServer extends Application { ObjectOutputStream p1out; ObjectOutputStream p2out; int PLAYER1 = 1; int PLAYER2 = 2;
I am having trouble with a mouse click method. In short I have a hexagon grid, and every time I want to click on one particular hexagon I want the color of the hexagon to change to blue(by default the color is grey). This part works, but when I go to click on another hexagon I want the color of the previous hexagon to change back to grey while at the same time changing the color of the current hexagon clicked to blue. So in other words, I only want one hexagon blue at a time. How might I do this?
I have a hexagon class for one particular hexagon, and a hexmap class for multiple hexagons. I know I should probably be handling mouse clicks in the hexmap since it deals with the whole thing. But I cannot say something like hexagon.setColor within a mouselistener in that class(it gives me a lot of issues). Here is some of my code :
public class Hexagons() public Hexagons(HexMap theMap, int mapRow, int mapCol, int width, int height) { this.map = theMap; this.row = mapRow; this.col = mapCol; this.width = width; this.height = height;
I am new to OOP, i am not sure if this is the correct approach or not. Write a class named CreditCard that has (at least) the following member variables:
- name. A String that holds the card holder's name. - cardNumber. A field that holds the credit card number. - balance. A double that stores the current credit card balance. - spendingLimit. A double that stores the spending limit of the card holder. - Bonus: additional fields that you can think of.
In addition, the class should have the following member functions:
- Constructor. The constructor should accept the card holder's name and card number and assign these values to the object's corresponding member variables. The constructor should initialize the spending limit to $2,000 and the balance to $0. - Accessors. Appropriate accessor functions should be created to allow values to be retrieved from an object's member variables. - purchase. This function should add the amount specified as a parameter to the balance member variable each time it is called. - increaseSpendingLimit. This function should add 500 to the spendingLimit member variable each time it is called. - payBill. This function should reset the balance to 0. - Input validation: Whenever a credit card number is modified, verify that it is of reasonable length.
Demonstrate the class in a program that creates a CreditCard object and allows the user to change and view the state of the credit card with a menu driven program.
View Card Information.
- Purchase an Item: ask the user the purchase amount and increase the card balance accordingly. - Pay Bill: call payBill method to set the balance to 0. - Increase Spending Limit: ask the user how much the spending limit should be, and call the increaseSpendingLimit function the appropriate number of times.
[CODE]
import java.io.*; import java.util.Scanner; public class CreditCard { Scanner input = new Scanner(System.in); //data members private String holderName; private int cardNumber; private int accountBalance; private double spendingLimit;
My code is giving me an error at the main method and it says that modifier 'static' is not allowed in constant variable declarations. every program that i searched for had the same code line but none had the problem i do.
I've come across an interesting problem when using a Jcombobox as a custom cell editor(and renderer) in a jtable. I was hoping to add a keybinding in order to display the dropdown of the combobox instead of having to click on it however, when I make a call to showPopup() I get:
Exception in thread "AWT-EventQueue-0" java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location Which is strange as my jtable is visible and the editor/renderer seems to be working fine.
Here's the cell editor + renderer I'm using:
class MyComboBoxRenderer extends JComboBox implements TableCellRenderer { public MyComboBoxRenderer(String[] items) { super(items); } public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) { if (isSelected) { setForeground(table.getSelectionForeground());
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 using a static method to convert a string to an Integer object. Next using a instance method to convert Integer object to an int.
Compiler is giving me two "cannot find symbol" errors:
One pointing to the dot operator between "Integer.valueOf(s)"
The other pointing to the dot operator between "obj.intValue()"
I have latest JDK installed: jdk-7u51-windows-x64.exe
Looks like JCL installed correctly with rt.jar file located in "lib" directory under "Program Files"
Following is source code:
Java Code:
public class StringToInt { public static void main (String args []) { String s = "125"; Integer obj = Integer.valueOf(s); int i = obj.intValue(); i += 10; System.out.println(i); } } mh_sh_highlight_all('java');
What I want to do is have a label that is updated whenever an object gets some new, relevant data.The way you do it in Java looks different from the way we do it in Objective-C. In Objective-C, we have what's known as a protocol. An Objective-C protocol is almost exactly like a Java "implementation." In Obj-C, if I want the user to see the address of where he is, I can have an object that gets the information and invokes a view controller's method; at that point, the view controller would then take the data passed to it and display the data in a label. However, the view controller is an instance of a subclass of the bundled view controller class.
I am new to java and still learning. I am trying to execute the code below which compiles successfully, but getting the following error:"Exception in thread "main" java.lang.NoSuchMethodError: main"
Code:
class Dog{ int size; String name; String breed; void bark(){ System.out.println("woof woof"); } } class DogTestDrive{
My program was working fine and then without changing anything, it has started throwing me a "Exception in thread "main" java. lang. NoClass Def FoundError: medina/client/ClientGameFrame". I'm dumbfounded as to how this can just suddenly appear after I've been working on this program all week. My research has pointed out that it must be my class paths but as far as I know, the class paths are fine....and why would it suddenly stop working if it was my class paths ?
I have just been trying to compile in netbeans and that's when the error occurs, though I just tried packaging to a jar and the jar works fine...though why not in netbeans?
import java.io.Console; public class Introductions{ public static void main(String[] args){ Console console = System.console(); console.printf("Hello!My name is ---"); } }
Output :-
Compiling Introductions.java....... -----------OUTPUT----------- Exception in thread "main" java.lang.NullPointerException at Introductions.main(Introductions.java:5) [Finished in 2.2s with exit code 1]
public class Emp { private String name; private String jobTitle; public void setName(String nameIn){ name=nameIn;
[Code] ....
<terminated> TestClass Exception in thread "main" java.util.NoSuchElementException: No line found at java.util.Scanner.nextLine(Unknown Source) at TestClass.payOneEmp(TestClass.java:21) at TestClass.main(TestClass.java:13)
I'd like to know how to return a new array, I wrote in a method below the main method. I want to print the array but system.out.print doesn't work for arrays apparently. What structure i should use?
I have to write a method called censor that gets an array of strings from the user as an argument and then returns an array of strings that contains all of the original strings in the same order except those with length of 4. For example if cat, dog, moose, lazy, with was entered, then it would return the exact same thing except for the words with and lazy.
Currently, my code so far just prints [Ljava.lang.String;@38cfdf and im stuck.
import java.util.Scanner; public class censorProgram { public static void main (String args[]){ Scanner input = new Scanner (System.in); System.out.println ("How many words would you like to enter?"); int lineOfText = input.nextInt();
[Code] ....
I have to make new string array in the method and return words without four letters in the main method
I am just trying to test this array, for a locker combination program that involves classes...but the array is printing out the whacky numbers for the location. When I try to call the method in the main, it does not work. How do I call a method that exist within a class into the main method?
public class locker { public static void main(String[] args) { CombinationLock();
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++)
