I am new to Java and have been learning it. I have a question here. I came across the following Java class and trying to understand it thoroughly but got confused how it is able to call an abstract method. Here is the code I am referring to :
package sampleapps.gui;
import javax.swing.*;
import java.awt.*;
public class InnerClassAnimationExample {
int x=70, y=70;
public static void main(String[] args) {
[Code] ....
So, in the code above, there is an inner class NewMyDrawPanel which has a paintComponent(Graphics g) method. I have highlighted 2 lines of code above.
Line 1 : Graphics2D g2d = (Graphics2D) g;
Line 2 : g2d.fillOval(x,y,40,40);
I understand we are type casting reference g to Graphics2D reference g2d and we are calling fillOval() method on g2d. I don't see a fillOval() method in Graphics2D class but it is there in Graphics class and fillOval method is an abstract method.
So, my question here is :
1. If we are not able to instantiate an abstract class(Graphics2D and Graphics classes), how are we able to access the fillOval() abstract method,
2. Secondly, since the fillOval() method is an abstract method, it does not have any implementation for the method.
However, when I call the method fillOval() on Graphics2D reference, I was able to draw and fill an oval of the specified co-ordinates. So, where would the actual implementation code be?
I am trying to call a java method in jsp. The main idea is to hide menu based on the user who logs in. The java class flows like this :
public class UserVerification { public static void main(String[] args) { UserVerification obj = new UserVerification(); System.out.print(obj.GetUserVerification("abc"));
I used java and jsf. I created dynamic datatable in java file. Can i call java method from setOnchange() event?
I am able to call java script function from setOnchange() event. See the below code which is working fine for java script.
HtmlSelectOneMenu selectOneMenu = new HtmlSelectOneMenu(); selectOneMenu.setStyleClass("dropdownStyleTwo"); selectOneMenu.setOnchange("openWin(this);IGNORE_UN LOAD=false");
I wrote openwin() function in java script. But i am not able to call java method change().
Code which is not working.
HtmlSelectOneMenu selectOneMenu = new HtmlSelectOneMenu(); selectOneMenu.setStyleClass("dropdownStyleTwo"); selectOneMenu.setOnchange("myclass.change();IGNORE _UNLOAD=false");
myclass is the bean of class Test. If user select any value from dropdown i want to call change java method. This function will apply the same selected dropdown value to the other record also.
My question is simple : I only own a List<Object>How can I set each element of _instanceMethod parameter from my List ?? If i decided to iterate through my list such as :
for (Object obj : myList){ _instanceMethod(obj); }
How can I correctly "populate" the _instanceMethod varargs signaturee by the n elements of my list ?
I have a question about a method I have. In my game, I had a move method to move my player left and right, and originally this method was huge, as it also took care checking collisions and a few other things. I broke it up a bit and put the collisions in their own methods and call them from again another method... Here is an extract which I hope illustrates my point:
private static final double MOVE_SPEED = 0.2; private static final double MAX_MOVE_SPEED = 3.5; private static final double STOP_SPEED = 0.18; private double xPos; private double yPos;
[Code] .....
Something I thought might be a good idea is to check the direction collision when im doing the calculations for that direction:
Then I thought instead i can check it after both of these steps:
if(moveLeft || dx < 0.0) { checkLeft(); }
I guess my question is quite general: How much is acceptable to break up a method? How many chains of method calls is acceptable? Is it ok to call the same method from different nearby places?
i am trying to create an applet with drop-down lists. When I compile the program the following error message appears '. . .is not abstract and doesn't override abstract method action Performed. . . Here is my code . . .
import java.awt.*; import java.awt.event.*; import java.applet.*; public class DavidApplet extends Applet implements ActionListener //class header { Label fName=new Label("First Name");
How do I create an instance of a class in a method?
I am a bit rusty whenever I think of instances. I always think of main method and objects when I see instance which gets me confused on what to do when I am not in a main method. The example:
I have a abstract class, School, and inside School I have some methods that must preform some action on an instance. For example, there is a move() method that must move the instance of School. Another method named, personOld(), which returns whether or not an instance of School surpassed some determined age.
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();
I've never had to do a void method call. I have my void method in one class and my main (where I want to do the call) in another. How do you actually call a void method?
My code has a method where the users input a bunch of variables and then those variables get added together in a new variable. What I want to know is how do I call the variable that is in the other method to another method?
import java.util.*; public class Calc{ public static void main (String [] args){ determinevalue1(); determinevalue2(); determineTotalvalue(double value1, double value2);
I am trying to get the program to ask the user to enter the project grade and if it is less than 65, then I want the program to display "fail" or if it is greater than 64 than I want it to display "passed". In this project I have to include a method and I am trying to call it in my if-else statement. I keep getting an error message saying "Project.java:143: error: incompatible types: void cannot be converted to int". I posted my code below. It's a long program, but this part is toward the bottom.
import java.util.Scanner; public class Project { public static void main(String[] args) { //call method welcomeMessage();
I have two comboBoxes - one in main and another in my 'windows' class. The code below is in main and references the comboBox in main but I need to use the comboBoxEnv out of my 'windows' class. How can I do that so it says ComboBoxEnv rather than comboBox?
JMenuItem menuExport = new JMenuItem("Export"); menuExport.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { if(comboBox.getSelectedItem() == null){
[Code] ....
I've gotten access to it by changing my code and making a method of it but I'm not sure of what I do now
private String eventName; private ClockDisplay timeOfEvent; public static final int MIDNIGHT_HOUR = 00; public static final int MINUTE_ZERO = 00; }
How can I create a method called public void addMinuteToTimeOfEvent() which calls the timeOfEvent's increment() method to add one minute to the timeOfEvent?
why don't I define my methods in a class, rather than going a level up and declaring it first in an abstract class/interface? If the point is to have different implementations for different needs, then we have the option to override the methods.
I am currently drawing graphics onto a JPanel, by overriding the standard paintComponent method.
Is it possible to call a method to draw some predefined shapes, instead of filling this method with all the stuff I need drawn, and if so, how do I do that?
And the servlet handles the HEAD method in the sense that the doGet() method returns if the method type is HEAD.When I run it, the servlet returns the code returned by the entire doGet() method. This shows that the doGet() method does not realize that it is a HEAD method and it should return back without processing further.The application server is Tomcat 4.0.
I am writing a program to take user input in order to create an array, then call a void method that will read in the numbers (from user's input) and fill the array.This method must use a loop to do this.(The array is to be passed to the void method as a parameter)
in theory, this should change the contents of the array, but without returning a result. Because it is a void method, the array is only passed through the method, not returned; Am I correct?How can I return the array and display it without having to change my method type?
public class Program7Array public static void main(String[] args) { // main method int howMany = Integer.parseInt(JOptionPane.showInputDialog(null, // user decides how long array is "How many numbers are there?")); double [] numbersArray = new double[howMany]; // creating the array makeArray(numbersArray, howMany); // calling the array
my arraylist is declared in my main method. A string that i will be calling on is declared in my main method as well. The arraylist and string is passed to a method outside the main. I am to search for the beginning of a string and end of the string, remove those items. Then i am to pass the string with the removed items to arraylist that is called in my main with an enhanced for loop. The for loop then displays what is needed from the string and the method i created. I will posting an example of my main and method that is used in my program.
public class ExampleUrl { public static void main(String[] args) throws MalformedURLException, IOException { ArrayList<String> urlList = new ArrayList(); String url = "";
I can call a child method from a main method. If I have a parent called "Assessment", a child called "Quiz", and another child called "test". Can I instinate an object like Assessment a = new test(); and call a method in test.I know the method can be called if I instinate the test t = new test() but that defeats the purpose of inheritance which I'm learning in class.
javax.servlet.ServletException: javax.ejb.EJBAccessException: JBAS014502: Aufruf an Methode: public abstract void de.dpunkt.myaktion.services.OrganisatorDAO.save(de.dpunkt.myaktion.model.Organisator) von Bean: OrganisatorDAOBean ist nicht gestattet javax.faces.webapp.FacesServlet.service(FacesServlet.java:606)
which translates to: call of method: .... from Bean ... is not allowed
But the naamSpeler.laatKaartenZien(), which returns a string, doesn't show on the label. Is there a way to call a method and use a html text on a label?
The name of the thread should be "call method in html text on label"
