I'm new to Java and have been stuck on how to use a final declaration statement once it's made. Below is a class I'm creating with the intention of calling it under a main method. I don't understand if I'm supposed to do anything else, like do some sort of get/set, or if the final static line is all I need. And, I don't know how I call it to the main method once I do.
public class Shirt//class name. { int collarSize;//data field. int sleeveLength;//data field. public final static String MATERIAL = "cotton";//final data field for material.
I've been into java for about 4 months now, No complaints so far, it's pretty awesome! So I understand Polymophism pretty good, I did some Animal classes and it worked out neatly.
However. I just can't seem to find my way in OOP when trying to implement in on a Calculator Class I wrote. As you mind know, a calculator can be separated into many classes. But I actually just want it to be separated into some OO like: | Calculator | CalcGUI | CalculatorFunctions | CalcRun.
I tried separating the single Calculator class, however, my calculator Buttons didn't work after that, anymore..
I am trying to create a GUI interface in swing which consists of four classes: a GUI class, which creates a main JPanel, a label, and a JList, which it takes from the second class, a MovesList class that contains a JList and the stuff needed to interface with it. It also has a main class, which basically just creates an object of the GUI class for the main window, and an Other class from which I would like to be able to add an item to the JList. I created methods in the MovesList class to get each component (like getMoveslist, or getMovesListScrollPane), which I then used to create the JList in the GUI class. I also created an addMove method so that I can add an item to the JList from any class through a MovesList object. However, this addMove method only works when called from the GUI or MovesList classes -- it does nothing when I collect from the Other class.
Here is my code:
//Main class public class TestProject { public static void main(String[] args) { GUI mainWindow = new GUI(); mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
[Code] ....
When I run this code, I get a window with a JLabel that says "Moves," and a JList that contains five elements -- test 1-test 5, but not a sixth "test from other class." ( using the add move method ) However, when I click on the window, the addMove method is also called, and successfully adds "test 6" to the list.
I've used Netbeans IDE to create a simple Swing JFrame container, class NewJFrame.
NewJFrame calls another JFrame with dialog in it. Problem is there is an endless call made to it. Here's the issue relevant piece of code:
//Code for calling class package p; public class NewJFrame extends javax.swing.JFrame implements ActionListener { ......... public NewJFrame() { initComponents(); //IDE auto generated code for binding
[Code] ....
I searched but i cannot understand why run class is getting called multiple times. I have attached the screen prints for both the screens. 2nd screen print(of called class) is very shallow since screen was blinking unstopped due to multiple calls, but i have attached a faint image of it.
I have wrote the necessary program for the class which was : Modify the customer class to include changeStreet(), changeState(), and changeZip methods. Modify the account class to include a changeAddress() method that has street city and zip parameters. Modify the Bank application to test the changeAddress method.
The problem arose when I went to test it. For some reason when it asks "Would you like to modify your account information? (y/n)" it will not allow the user to input anything and thus test the class. Here is my code
Class Customer import java.util.*; import java.io.*; public class Customer { private String firstName, lastName, street, city,state, zip;
Netbeans tells me it's an illegal start of expression during the initialisation of the interactWithUser method. public class InvertLetter {
/** * @param args the command line arguments */ public static void main(String[] args) { /** * String mit den Kleinbuchstaben. */ final String lowercase = "abcdefghijklmnopqrstuvwxyz";
Let's say within a class I create a method that takes care of creating a java swing layout with labels, buttons etc.. then attach an action listener (inner class) for each button to change a respective label text. All I would need is that the action listener method can access and modify the label as needed.
Have read about static, protected, private, getters and setters but honestly bit confused about which structure should be adopted as a best practice. Global static protected variables for the labels along with private inner classes implementing ActionListeners believe will do the trick and will be able to access the labels but not convinced this is good practice.
import java.util.HashSet; import java.util.ArrayList; public class Graph { double [] [] adj; graph (double [] [] a) { adj= new double [a.length][a.length]; for (int i=0;i<a.length;i++) for (int j=0;j<a.length;j++) adj[i][j]=a[i][j]; }
C:UserscDesktopGraph.java:: error: invalid method declaration; return type required graph (double [] [] a)
So from what iv learnt in Java and programming in general is that using a case statement is far more efficient that using multiple IF statements. I have an multiple IF statements contained within a method of my program, and would like to instead use a case statement.
I am not able to understand what does this URI exists at all ?? I feel it making things complex and meaningless or else i am missing something hidden and secret.
Whilst pre-preparing for java certification, one of the online mock exams has slightly confused me by saying my answer was incorrect for multi-dimension array 'declaration and instantiation'.
This is one of the answers i chose - which was marked as incorrect
a) int[][] array2d = {{123}, {4,5}};
Which looks absolutely fine to me.One of the other answers, which i agree is correct and so does the mock exam is
when a new object is created in Java it follows the idiom:
Object obj = new Object(); where the Object() constructor matches the object type Object.
But what if it doesn't? I understand from the Oracle Docs on creating objects and polymorphism that the constructor must be in that object's class or one of its subclasses. However, suppose we wanted to declare a new stack. My first instinct would be:
Stack s1 = new Stack(); But I assume it's valid to do it this way, too:
Object s2 = new Stack(); // Is there a difference here? What are we really saying about s2? I'm guessing s2 is simply an empty stack, but only has access to the Object class methods? I'm not sure why someone would ever do this, but I want to solidify my understanding of the Java hierarchy. Are there really any circumstances where someone would use a subclass's constructor when creating a new object?
I have one interface with three(more than one) method declaration. In the subclass that implements it I want to define only one method not all three not even blank definition of them.Is there any keyword or method for that. How to do it? Is it possible to do it? In GUI we use adapter classes to achieve it. What for console application?
What is exact difference between them? Another thing is when I check (a==b) it retuns me false, but when I check a.equals(b) it returns me with true. Why So?
I have an application that uses an object that is declared globally for the class. Within a method that is triggered by a user event, it creates a new object and assigns it to this global object declaration. My question is, when the object is overwritten multiple times by the user selecting the button that calls this method, will the older instances be garbage collected or is there still a reference to them? Is there any downfall to this logic and if so what would be a solution.
I am trying to make a game, for some reason i have begun to get a java.lang.StackOverflowError.
I am not exactly sure how i can fix it. only removing line 14 from infopannel1 (and everything that used that class.) seems to work. im not sure what else i can do to fix it. or why its resulting in stack overflow for that matter.
I am putting in a link for the files i wrote this using bluej (several classes have no relevance, errorv2, demonstration, folderreadertest, ReadWithScanner, saveloadtest, menutest,rannum, and menutestTester. are all irrelivent to my problem.)
I came across this code which proves that variable initialisation occurs before even constructors are called.However, I am confused over some things.
Firstly, from my understanding, when a new House object is created in this line House h = new House(); , the no-arg constructor of the House class is called.
Since the no-arg constructor House() is called, why are all the creation of Window objects being run first ? Shouldn't Java jump straight into the no-arg constructor House() ?
class Window { Window(int marker) { System.out.println("Window(" + marker + ")"); } } class House { Window w1 = new Window(1); // Before constructor House() { // Show that we’re in the constructor: System.out.println("House()"); w3 = new Window(33); // Reinitialize w3
I have to implement all the stack methods in java such as push, pop empty, not using the ready methods but have to create them and to execute an exercise but is sth wrong with it
public class Stiva {
/** the problem is here how to declare the stack 1 and stack 2 and kreu(head) gjmax(size)*/
int Gjmax; int array[] = new int[Gjmax]; int kreu; private Stiva stiva1; private Stiva stiva2;
I am using netbeans 7.2, glassfish 3.1.2, JSF 2.1 and Primefaces 3.2. When I add more than three menu tabs, I get this error ui layout initialization error the center-pane element does not exist the center-pane is a required element. This is my template.xhtml code:
<?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:p="http://primefaces.org/ui">
