How To Handle Classes Interacting With Each Other
Mar 16, 2015
So my question is simply about how to best lay out my code so that each classes are talking to each other in the best way possible. I have a habit of creating a "handler" that just holds instances of either class and make them interact such as a player/map handler, that holds an instance of a player & map and then checks things such as collisions, though i'm not sure if this is the best practice. i'm just trying to make sure i'm always laying out my code the best way I can as I tend to get a little messy
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Feb 14, 2014
I am writing a code that I want only to accept numbers 1 through 8 and to recognize when it isn't an integer being put in. I tried the following:
Java Code: int classSelect = keyboard.nextInt();
try
{
while( (classSelect<1 || classSelect>8))
[Code]....
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Apr 14, 2014
In my EJB modules, to prevent that any JPA exception is ever thrown, I check the condition that would cause the exception beforehand. For example, the exception javax.persistence.EntityExistsException is never thrown because, before persisting the entity, I check if such primary key already exists in the DB. Is it the right way to do this?
Another approach is too allow the JPA exceptions to be thrown and catch them in a try-catch block, and then throw my custom exception from the "catch" block. However it requires to call EntityManager.flush () at the end of the "try" block. Otherwise the exception throw could be deferred and never be caught by my block.
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Sep 16, 2014
how we can handle the string with special characters. For instance:
123456789BNJKNBJNBJKJKBNJKBJKNBJK"VJKNBJNHBJNJKBVJ KBJKNB"VHBVBBVNBVNBVBVBVBNBVNBNBJHFBVFJB FNVJBNVJNVJDFNVJKNVJKNVJKVNNVJ NN"
I get some user inputs with double quotes and i need to split to 80 chars line.
.length fails to get the length if it contains special characters like double quotes and ?
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Feb 25, 2015
I have an ecommerce site that has about 100000 SKUs. What is the best practice for handling all the product images as far as where to store them and how to display them on the pages? Should I have a separate HTTP server to serve the images?
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Sep 18, 2009
I am trying to execute the a command using process builder. But that command is having some Japanese Character. So it is executing the command but result is not as expected.
command i tried : 1) echo 拝見 マイクロエレクトロニクス 2) mkdir "d: est拝見 マイクロエレクトロニクス"
OS: XP SP2
result: some chunk char are getting displayed.
See here a sample code which i tried ...
String commandNotWorksFine ="echo 拝見 マイクロエレクトロニクス";
String charSetname = "Shift_JIS";
String[] envArr = new String[] { "cmd", "/c", commandNotWorksFine};
ProcessBuilder builder = new ProcessBuilder(envArr);
Process p = builder.start();
[Code] ....
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Jan 7, 2015
I have come across some code where it attempts to save an entity to a database, but before it does it validates that the name of the entity is unique. If it is not unique it throws a runtime exception. This results in the ugly default exception web page being displayed. Is there any way to propagate this back to the JSF page where the user enters and clicks the form button to save the entity? The page already handles some error cases such as "field required" using the h:inputText's 'required' attribute. Need something more for name validation.
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Apr 2, 2014
Every type of controllable object in my game is a type of Entity, and so extends Entity. This is broken down into Ship(s) and Structure(s). But I have different types of structures as well. The problem is that I use an ArrayList<Structure> to store all of a team's structures, but I need to be able to loop through that, and still be able to reference the subclasses of those structures.
For example, I have a JumpGate, which extends Structure. I need to be able to reference a particular JumpGate - as a JumpGate - and not as a Structure. However, the way that I cycle through all of the different types of structures is with an ArrayList<Structure>. I could get around this by having an ArrayList<JumpGate>, however, I would then need a seperate ArrayList for every type of Structure, which would get messy.
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Oct 11, 2014
How is this possible? Here is the servlet page.
/**
* Servlet implementation class InvoicingDeptServlet
*/
@WebServlet("/InvoicingDeptServlet")
public class InvoicingDeptServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
//Make arraylist global object
ArrayList<InvoiceData> invoiceList = new ArrayList<InvoiceData>();
[Code] ....
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Apr 22, 2015
I have a project that is asking me to create a program that will handle a Golfer and his scores. The program will be comprised of three classes: a Golfer class that will manage all the golfer's scores, a Score class and a Tester class to drive the other classes. To accomplish this task the program will use a partially filled array to store the golfer's scores. I have the majority of the code written. It compiles fine, but when I compile and run it only gives the following output.
Tiger ID Number: 1001 Home Course: Pebble Beach
Score Date Course Course Rating Course Slope
[LScore;@15db9742
I am not sure what I am doing wrong. I have been over and over the code. It is also only printing one golfers information. I have tried creating a for loop for the for the toString in the Golfer class but I am getting the following error Golfer.java:117: error: missing return statement.
I am at a loss here is the code I have for the three sections.
public class Golfer
{
private String name;
private String homeCourse;
private int idNum;
private Score[] scores;
private static int nextIDNum = 1000;
[Code] ....
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May 6, 2015
I can't find an handler or a listener to intercept the 'Save as' window that should pops up when i click on a download link in a webview embedded page.
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Jun 2, 2014
I want to ask if there is an option to set the vertical position of the node handles of the TreeView-control.
I used a custom TreeCell factory with icons of sizes between 24 and 64 pixel and the location of the handle is regardless of the size of the icon on top of the cell. So if you got large icons the view did not look so nice.What I want is a property or something to center the handle in the cell depending on the size of the cell. Is there such an option?
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Jun 25, 2014
I have a page which lists items using a ui:repeat. The repeat is surrounded by my h:form tag.
Now I have made it so that when click an item, then I load some item details - render them in their own xhtml file and inject the result into the dom tree.
This is causing some problems.
* My injected content has commandButtons and commandLinks which do not work because I don't have a form in my injected page - since this would cause nested forms :-(
* tried to replace commandButtons and commandLinks and instead create unique url's that I can call to get my work done - but how to I then re-render a panelGroup on then page? tried using jsf.ajax.request but I'm not able to get part of the page (a shoppingcart) to update
Basic outline
<h:form>
<table>
<ui:repeat ...>
<tr><td onclick="...">Click here to load item details</td></tr><tr><td id="itemDetailPlaceholder"></td></tr>
</ui:repeat>
</table>
</h:form>
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Jun 24, 2014
Having with LSL and JSF working together? The only thing I have gotten to work with LSL is PHP, and I know I could get JSP working with it with a little research. However, I rather not mix them on my server.
The only requirement for LSL to work with it is there needs be a custom page that can handle get and post request directly. I have not done this with JSF yet so I'm wondering how that would look.
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Jul 16, 2014
I need to write server side program(Servlet) which must be access by several requests at same time.how to handle this using java? Do i need to use queue or multiple instance of same class. Any example server method which returns the results based on ID
public String getResut(int id){
1)get db connection
2)get the result from db
3) retun the result
}
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Jun 25, 2014
i'd been using Opencsv to upload all this data into my Db(Postgres) using EclipseLink with batch inserting, it wont take more than 5 secs to load 200k+ data cause all the columns are of type string so theres no format require, the problem comes when i need to give a special format to the data that is in this table (date, Integer, etc).
Right now how it works:
- Ill go row by row (when its required) verifying the format of the data and convert it with something like this Ex: Date date = Fechas.strToDate(data, Pattern) and fill the new Object with this info
what i'm planing to do
- With the function of EclipseLink OPERATOR im gonna use that to change all the rows of a column that requires a NUMBER format with OPERATOR('ToNumber',column1,'9999999999')
i cant do the same for Date cause ill get an error if the data doesn't have a Date like pattern
how to handle this Date formatting(from a query, or directly in java).
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Sep 4, 2014
How to catch the event when table view's column are re-positioned. Basically when the column is re-positioned from 1 position to 5 position , i want to do update the db.
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Apr 18, 2014
How do you call classes within other classes? Or can you only call classes through the main?
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Feb 14, 2015
I'm doing an aggregation exercise that's suppose to find the volume and surface area of a cylinder. What I'm trying to do is pass values from one class, to a second class, and that second class passes values to a third class.
This may be a clearer explanation: The first class is the main program which sends values to the second and third class. The second class is used do calculations for a circle (a pre-existing class from another assignment). The third class grabs the values that the second class calculated and calculates those values with the one that was passed from the first class to the third class. The first class then prints the outcome.
Problem is when the program gets to the third class, it just calculates the value from the first class with the default constructor from the second class. It's like the second class never received the values from the first class. I think I'm missing a step, but I don't what it is.
First Class:
package circle;
import java.util.Scanner;
public class CylinderInput
{
static Scanner in = new Scanner(System.in);
public static void main(String[] args)
{
//user defined variable
[Code]...
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Dec 26, 2014
Why do we get such output or which line of code produces the output?
1class Egg2 {
2 protected class Yolk {
3 public Yolk() { print("Egg2.Yolk()"); }
4 public void f() { print("Egg2.Yolk.f()");}
5 }
6 private Yolk y = new Yolk();
[Code] ....
/* Output:
1.)Egg2.Yolk()
2.)New Egg2()
3.)Egg2.Yolk()
4.)BigEgg2.Yolk()
5.)BigEgg2.Yolk.f()
*///:~
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Oct 18, 2014
I'm quite new to Java. I have some trouble with understanding how to get two classes to get objects from each other (if that is the correct term).
Lets say I have a login class, in which I have a method checking what the user has entered into the console (I have not displayed the whole code, but this class works as it should and give the user an option to enter username and password and return it true if entered correct).
public static boolean validateUserPass(String userName, String password) {
String[] user = {"admin"};
String[] passwords = {"firkanten"};
boolean check = false;
for (int i = 0; i < user.length; i++) {
if (userName.equals(user[i])) {
if (password.equals(passwords[i])) {
check = true;
Now, in another class I want a display box to appear on the screen and give the user three options: Click yes, no or cancel. I get this to run perfectly alone, this is not the hard part for me. I want the display box only to appear when the correct username and password is given, but I can't seem to figure out how to do this probably.
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Feb 7, 2014
Regarding the code examples in Head First Java, this is from Chapter 5, regarding the beginning creation of the dot com game. There are two classes in quesiton
the first is the SimpleDotComTester class:
public class SimpleDotComTester {
public static void main(String[] args)
{
SimpleDotCom dot = new SimpleDotCom();
int[] locations = {2, 3, 4};
dot.setLocationCells(locations);
String userGuess = "2";
String result = dot.checkYourself(userGuess);
}
}
and the second one is the code for the checkYourself () method in the SimpleDotCom class
public class SimpleDotCom {
int[] locationCells;
int numOfHits = 0;
public void setLocationCells(int[] locs)
[code]....
Now I noticed that both classes use a variable called result; the program runs fine, but assume from the example that you can use the same variable name two different classes;
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Mar 29, 2014
design a class to conduct a survey of three hospitals. you want to know how many sectors (eg operation, children, gastronomic) each hospitals have, and how many doctors there are in each sector.
what is the process of class design?
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Jan 5, 2014
I have a Date class and Time class. Is it possible to pass Time object inside Date constructor so that toString function gives output as 12/05/2013 06:31:30 ?
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Apr 24, 2014
I have two classes.
First and Second.
In First class I want to use methods from Second class. So:
Java Code:
Second s = new Second();
s.secondMethod(); mh_sh_highlight_all('java');
Second thing I want to do is use JTextArea from First class in Second class.
So since it gives me error, I extended First class with Second:
Java Code: public class Second extends First { mh_sh_highlight_all('java');
It look like it should work, no errors etc. Also both things are working separately. But since I used both at once...
Java Code:
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at package.Second.<init>(Second.java:7)
at package.First.<init>(First.java:17) mh_sh_highlight_all('java');
I can move what I need to First class, and it will work fine, but I want to make this in two classes. But I really don't understand extends, I just use them if there is need for them. So I don't know how to handle this problem.
I also tried to extends Second just like First:
Java Code: public class Second extends JPanel implements ActionListener { mh_sh_highlight_all('java');
Instead of extending First, but it can not be done, since ActionListener is in First...
Well. Also addActionListener can maybe solve my problem?
I'm using:
Java Code: xx.addActionListener(this); mh_sh_highlight_all('java');
Maybe I can use something instead of this? But what?
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Jan 19, 2015
Wondering, what is exactly reason for existence of inner classes? Are there problems that without them you can not resolve?
Anything beside emulate multiple inheritance - when your class need to extends the real classes, and not implement multiple interfaces ?
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