Dynamic Method Creation
Aug 8, 2014
I am trying to create a Android game. The game is a card game, where each card has a different action and has a different effect. My first thought was to create a Card class and somehow dynamically change the action method for each instance. However after a little bit of research it seems that may be too difficult. A different idea is that I create a class for each different card, and therefore can define the action method different for each one. However currently there is at least 300 cards and therefore I would need 300 different classes, which seems excessive.
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Jan 9, 2014
Why is the equals-method in the super-class invoked? Shouldn't the equals-method in the sub-class be invoked(at least in the first if-statement since b2 is a B(i know B is also an A))?Is the equals-method overridden? Or does B have its own equals-method?
class SomeClass{
public static void main(String[] args) {
B b1 = new B(123,1);
B b2 = new B(123,2);
[code]...
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Nov 7, 2014
How can I write a method that takes a string with duplicates letters and returns the same string which does not contain duplicates. For example, if you pass it radar, it will return rad. Also i would like to know how can I Write a method that takes as parameters the secret word and the good guesses and returns a string that is the secretword but has dashes in the places where the player has not yet guessed that letter. For example, if the secret word is radar and the player has already guessed the good guesses letters r and d, the method will return r-d-r.
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Apr 3, 2014
I am making a Java project using Eclipse,oracle 10g and Apache tomcat.
Now my problem is that I cant create a session for the users. I have coded on jsp pages mostly.
Session creation using HttpSession through servlets or jsp
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Mar 26, 2015
I know I'm missing something simple, but not sure what. When running the following I have to enter the name of the output file twice.
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
public class IODemo {
[Code] ....
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Feb 7, 2015
I'm making a code for a log in system that allow me to verify if username and psw are correct (using a file txt as refer), and then i will add maybe the possibility to sign up.
The fact is that I want this kind of formatting on the .txt
username psw
username psw
username psw
...etc
So I have to read the lines and split to the " " and compare the insert data and the read data.
Here is my code, it star but give me this error when i insert any word
XML Code:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at prova.main(prova.java:20) mh_sh_highlight_all('xml'); Java Code: import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class prova {
public static void main(String[] args) throws FileNotFoundException {
[Code] .....
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Jan 26, 2015
I am creating a simple tiled minecraft like game in java, but i dont know how to make the game loop.Here is the source:
package net.pltformgame.main;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
public class main extends JFrame implements KeyListener {
[code]...
I really dont know how i make the jump or the game loop.
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Mar 25, 2014
How could we create excel sheets(xls) in java?
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Oct 25, 2014
So, I've been working on creating a text-based game engine that would create games similar to Achaea. It's been working pretty well so far. I just finished creating a great mapping system, but now I've run into a problem. I have a mapping system, but actually creating a map would prove to be quite a lot of work. Each location that the player can be inside of has a name, description, map symbol, and an array of the things inside of it. How can I make some sort of map creation program or something so that I can create my maps more easily?
I thought perhaps making a constructor that accepts a list of files, the first containing a table of strings for the names, the second containing a table of strings for the descriptions, etc.; but it seems that would be quite tedious and may be more complex than actually just hard-programming maps.
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Mar 9, 2015
I have just started to learn Java and have come across a small bump in the road, In the book I am reading it shows an example program using java.io.File with the line File javaFile = new File("test.txt");
The program then goes on to ask if you would like to delete the file with a small do while loop.
Anyway, try as hard as I can I cannot located the test.txt file on my system! is there a reason for this? The program runs fine and has no errors and if I manually create the txt file it will delete it, but it doesn't seem to create the file in the first place.
Why the file is not being created?
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Mar 3, 2015
Now, I would like to properly stop the server. For that, I can do server.stop(); . However, this does not work since the object server is not public, it is contained within the public pc_proxy class.How do I do that?
Java Code: import java.net.*;
import java.io.*;
import com.sun.net.httpserver.*;
import java.util.concurrent.Executors;
import java.lang.reflect.Array;
[code]....
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Aug 15, 2014
I have a couple of objects, which I will call height and width. The latter may depend on the former and I access them through an interface:
interface Height
{
double getHeight();
}
interface Width
{
double getWidth( Height height );
}
I then have something I will call a RectangleMaker, which represents some set of rectangles that can be made. It takes a list of heights and widths and keeps track of which ones have been selected and which ones can still be made. For example, the possible heights might be 2 or 3 and the possible widths 3 or 4. It needs to determine if it can make a rectangle with a specific area and if selected to make that rectangle, disallow any other heights. So if I said, you are in charge of 2 x 3 rectangles, it could still potentially also make 2 x 4 rectangles, but 3 x 3 rectangles would no longer be an option. For the most part I think these details are irrelevant to my question, which is really about organization and assignment of responsibilities.
interface RectangleMaker
{
void setHeights( ArrayList<Height> );
void setWidths( ArrayList<Width> );
boolean isAreaAvailable( double Area );
void selectDimension( Height height, Width width );
Height listAllowedHeight();
ArrayList<Width> listAllowedWidths();
}
Now I have a new requirement. The lists of heights now need to be associated with a source, as do the widths. I should keep track of a list of RectangleMakers and pick the 'most appropriate' one for a particular area. The rule is to sort first on the height source and then on the width source and the first one able to handle the area, gets the job. So I created two enums heightSource and widthSource and had RectangleMaker implement Comparable, so I can make an ArrayList<RectangleMaker> and sort it based on the rules. Then I traverse the list and the first one that returns isAreaAvailable() true gets the job.
The final bit is that these sources also imply a specific set of Heights or Widths. How I get that set varies, it may be a fixed value or values, or might be read from a file. So in principle I could have:
ArrayList<Height> buildHeights( RectangleMaker.SOURCE source )
{
switch ( source )
{
}
}
and have a lot of specific code that builds each list by whatever method is appropriate. I still need to deal with the fact I might need additional information to build the lists. For example, one source might require a min, max and increment and another might require a file name. So I started working in the direction of more interfaces.
interface HeightList
{
ArrayList<Height> getHeights();
RectangleMaker.Source getSource();
}
I am not totally comfortable with my enum lists. They solve the sorting problem, but I am not exactly sure which class should define them. Right now they are defined by the RectangleMaker. I would need to update this class every time I added an implementation of HeightList or WidthList.
I was also thinking that since the list is built from a specific source, that source should be associated with the list. That would lead me to make this change:
interface RectangleMaker
{
void setHeights( HeightList heightList );
void setWidths( WidthList widthList );
boolean isAreaAvailable( double Area );
void selectDimension( Height height, Width width );
Height listAllowedHeight();
ArrayList<Width> listAllowedWidths();
}
It seems maybe there should be a factory in here somewhere, but this is where I am having trouble sorting out exactly who has what responsibility. I can do this sort of thing with my HeightList interface:
class SpacedHeight implements HeightList
{
int start;
int end;
int step;
ArrayList<Height> heights;
RectangleMaker.SOURCE source;
[Code] ....
Should I be thinking of putting one more layer over all of this? What complicates my thinking are two things: multiple instances may have the same source and some of these instances are dynamic. For example, two SpacedHeight instances may have different ranges, but they are both SpacedHeight and it doesn't matter which gets picked first. Exactly what SpacedHeight instances get created is determined by prompting the user for the values. If the heights come from a file, every instance would be associated with a different source and the file names would be hard-coded.
I think I want to make a HeightFactory and I think then it would make sense to move my enum definitions there. I see how I would do that if I could hard-code a specific instance of a HeightList with a specific enum. I am less clear on how to handle the case where the factory needs different parameters for different HeightList implementations.
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Jan 21, 2015
I am working on a UI in JavaFX and create several instances of a custom control class. The control consists of a Pane which wraps several other containers, one of which contains a Circle shape.
At one point, I instance this control and access the Circle shape directly. I transform it's center coordinates (which are always {0.0, 0.0} ) to Scene coordinates. The problem is, the transformation always yields coordinates that correspond to the upper left corner of the control's root pane.
In other words, it's as if the Circle is positioned at the upper left corner of the custom control (when, in fact, it's positioned near the lower right corner).
I have other instanced controls already in the scene, and they do not have this issue - converting the Circle's coordinates to scene coordinates works as it should.
It seems obvious that I'm accessing the Circle too soon - that perhaps the scene graph hasn't been fully traversed for the control and the Circle's position within the control's hierarchy hasn't been updated. I've verified that my attempt to access the Circle's center coordinates occurs after the control's initialize() method is executed, so how to ensure the control's scene graph has been fully updated before I try to manipulate the control...
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Oct 27, 2014
I'm trying to write a transparent proxy like polipo. Polipo is written in C and I want to have the same result in java.
A simple program that can filter/monitor all connections created and closed by the browser.
To do so, I've chosen to work with sockets, because that's the only way i know to read and write raw data to and from the browser in a completely transparent way.
In this moment my code reads and writes every couple of request/response but I've noticed profiling it that the time needed to create the socket is a bottleneck.
Using URLConnection to create the same connection I need much less time than sockets.
When socket creation implies 50ms URLConnection implies only 1ms.
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Mar 21, 2015
I have my code in 3 different files using encapsulation (Data hiding) and i have 1 problem at the very end of my code in my if and else statement (very bottom) when trying to call the classes from the other 2 documents. I will put the code in 1st document to 3rd document.
// FIRST DOCUMENT
public class CollegeCourse { //class name
//variables
String deptName;
int courseNum;
int credits = 3;
double fee;
[Code] ....
UPDATE: error message is
UseCourse.java:24: error: cannot find symbol
LabCourse lc = new LabCourse(department, course, Credits);
^
symbol: variable department
location: class UseCourse
UseCourse.java:24: error: cannot find symbol
LabCourse lc = new LabCourse(department, course, Credits);
[Code] ....
4 errors
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Dec 2, 2014
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:
@Test
public void receiveMessage() throws Exception {
MessageConsumer consumer = null;
ConnectionFactory connectionFactory = null;
Connection connection = null;
Session session = null;
Destination destination = null;
[code]....
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Oct 10, 2014
So I have this stack. I'm writing out all the operations and what not but I'm having trouble bypassing this "generic array creation" problem. I'm meant to be creating an array based implementation of a stack and from my research from google and my various attempts at things, I have not found a solution that works.
In addition; I have all the operations written that I need except for one final one. And that is clear(). clear() is meant to empty the array, essentially it is a popAll() method. Then all I need to do is set up so I can print out the arrays and I should be able to handle everything else.
StackInterface:
/**
An interface for the ADT stack.
*/
public interface StackInterface<T>
{
/** Adds a new entry to the top of this stack.
@param newEntry an object to be added to the stack */
public void push(T newEntry);
/** Removes and returns this stackÕs top entry.
@return either the object at the top of the stack or, if the stack is empty before the operation, null
*/
public T pop();
[Code] ....
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Oct 25, 2014
Create a one dimensional array which holds 10 values. Ask the user to input an index value between 0 and 9. Print the value the user selected. Be sure to explain the output to the user. That is my assignment, and here is my code:
import java.util.Scanner;
public class Array {
public static void main(String args[]) {
Scanner sc = new Scanner(System.in);
int a[]= new int[9];
a[0] = 10;
a[1] = 20;
[code]....
I don't know how to use the scanner to get someone's input properly.
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Nov 15, 2014
I have a web form with a field Department. I want to add Sub Departments(unknown number) of one Department and then further Sub Sub Departments(unknown number) of one Sub Department. How I will make a form and how I will add this data in attached database. I have one solution:
One Department field with a button to add any sub department if any. By clicking on button, a new row will be generated with another text field and new button. In this way, it will go on. Tree like structure.
But I have another solution, JSF Tree to add or delete entries on the run time. But the problem is that I am unable to find any example of JSF tree like structure populated from database and in which we can add or delete entries on run time and on the same time these entries may also be stored in database.
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Jan 26, 2015
In my application, users select the year and manage data for that year (for example, they can choose 2014 for managing invoices for 2014, then switch to 2015 and work with that year). Each year as his own database.
I'am able to change persistence unit connection at runtime with Persistence.createEntityManagerFactory(PU_NAME,map_with_connection_info) This procedure build a non-jta environment.
It is possible to create entityManager / entityManagerFactory with JTA ?
I don't want to create new persistence unit each year or each time a new database is required.
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Jan 30, 2014
I'm trying to implement an Office class that contains an inner class: WorkerNode. The WorkerNode class has a name attribute (String) and WorkerNode attributes for boss, peer and subordinate. The attributes of Office are manager and current which are WorkerNode references. The manager refers to the entry point of the structure and current is the current node in the structure. For simplicity, i'm going to try to limit it to 3 levels and assume that the names are unique. I've put together a Office class that containing main and provided the code I've worked on so far.
public class Office {
public static void main(String[] args) {
String name=Input.getString("input the manager's name: ");
Office office=new Office(name);
int option;
[code]....
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Jul 7, 2014
I'd like the GUI to be drawn based on definition file. Is it possible to "generate" fxml (like PHP does html) so I could do this:
for (...) {
command_to_generate (<button ....>);
}
?
Or is using legaxy javaFX code the only way to achieve it?
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Aug 3, 2011
I am trying to pass additional information through <a href> tag
<a href="welcome.jsp & param=<%=add.getID()%>">Welcome </a>
The error is : HTTP Status 404 - /WebApp/welcome.jsp & param=6
The id obtained from add.getID() is displayed in address bar on the browser.
I want to use this id on the next page. I try to use :
request.getParameter("param");
But could not get the ID....
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Apr 4, 2014
I'm trying to implement a functionality which will control the visibility of three outputText. I'm using a selectOneMenu, which has three options. Each option will enable visibility of one outputText, and rest will be invisible.
I used the following code
<h:selectOneMenu id="search" styleClass="select-box" value="#{empMB.showHide}" required="true" requiredMessage="Please Select an Option" >
<f:selectItem itemLabel="-----Select----"/>
<f:selectItem itemLabel="By Name" itemValue="1"/>
[Code] ....
Initially all outputText s is invisible as rendered value is false, but when I select different options, their respective outputText s are not visible.
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Aug 15, 2014
if, instead of an ArrayList, can I do the following to initialize a Dyanmic array ? :
First, in my class, I have :
class Example{
private int rows;
private int columns;
private AnotherClass[][] 2DArray;
public Example(int rows, int columns){
this.rows = rows;
this.columns = columns;
[code]....
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Feb 12, 2014
public class Fibonacci {
public static void main(String[] args) {
int[] numbers;
numbers = new int[20];
numbers[0] = 0;
numbers[1] = 1;
System.out.println("
[Code] ....
I wrote this program for my Java class to print out the first 20 numbers of the Fibonacci series. My assignment then tells me to Rewrite your program using dynamic array. I'm not sure how to do this.
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