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From what I think I read in your question, you want to do Ajax. This will allow you to put a request out to the servlet and process the result with Javascript inside the HTML without changing the actual browser page. Try jQuery to get this to work.
If you do not know what Ajax or jQuery are, you first need to do some reading. There is enough info on this on the internet.
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Hi i've created a canvas for game and an applet which contains this canvas and can communicate with my database. But when canvas goes into the game loop my applet doesn't respond anything i can't even close it. Also in my canvas' constructor method i make it's background black but it doesn't work either. Here is the code for 2 classes. And for now game loop is empty but i tried it with simple game loop which runs at 25fps and sleeps when needed.
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferStrategy;
public class GameCanvas extends Canvas implements Runnable{
private Graphics2D graphics;
private BufferStrategy bufferStrategy;
private boolean gameRunning;
public GameCanvas(){
setBackground(Color.black);
setSize(300, 300);
}
public void initGame(){
createBufferStrategy(2);
bufferStrategy = getBufferStrategy();
graphics = (Graphics2D)this.getBufferStrategy().getDrawGraphics();
gameRunning = true;
Thread t = new Thread(this);
t.run();
}
public void run(){
gameLoop();
}
public void gameLoop(){
while(gameRunning){
}
}
public void update(){
}
public void drawScreen(){
graphics.clearRect(0, 0, this.getWidth(), this.getHeight());
if(!bufferStrategy.contentsLost())
bufferStrategy.show();
}
}
import java.sql.*;
import javax.swing.JApplet;
public class DatabaseApplet extends JApplet{
Connection con;
static{
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
}catch(Exception e){
e.printStackTrace();
}
}
String url = "jdbc:mysql://127.0.0.1:3306/players";
String name = "root";
String password = "root";
GameCanvas gameCanvas;
public void init(){
setSize(300, 300);
add(gameCanvas = new GameCanvas());
try{
con = DriverManager.getConnection(url, name, password);
}catch(SQLException e){
e.printStackTrace();
}
}
public void start(){
gameCanvas.initGame();
}
public void destroy() {
try{
con.close();
}catch(SQLException e){
e.printStackTrace();
}
}
}
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public void gameLoop(){
while(gameRunning){
}
}
I cannot see how you get out of this loop, nor how it ever releases control.
Just say 'NO' to evaluated arguments for diadic functions! Ash
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First of all thanks for the answer. I'm running this game loop in another thread so shouldnt operating system take care of giving other threads clock time? And as i said before if i do something like Thread.sleep(freeTime) or Thread.yield() it doesn't work either. I tried it inside html and surprisingly it makes background black there. Also can you suggest how can i make a canvas game inside applet because there must be a game loop similar to this.
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Well I've copied your code and run it up in my IDE and that little closed loop really seems to block everything. I think you will need to redesign how you are doing this, although I can't offer any suggestions about how to do this in an applet without going back to the Tutorials[^].
Just say 'NO' to evaluated arguments for diadic functions! Ash
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I found a solution. When i use t.start() instead of t.run() it works correctly. Thanks for your replies again.
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hi i have worked in VB/C# where i created LAN enabled applications like apps for record handling and MIS/ERP solution type, now i have switched to java so i want to know a few queries as:
1. Do we have to go JSP/EJB for LAN applications or i can make them in core Java too.
2.if,its possible to create application like that in core java ,what kind of classes/packages i need for them(other then java.net) and 3rd party api's for simple working?
3. how can such application be going to interact with each other or do i need threads (thread executions) to make it understand about every process going between diiferent client and one server?
4. Is it not possible to achieve such facility with DB connection call with diff server ip/port instead of making the app to listen for its server and then work ?
5.in Above,, which one will going to be smooth in between them?
i know its too much in one go but if you can please solve my any query first you like 
In this world only the hardwork with smart approach wins.....
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Alok sharma ji wrote: 1. Do we have to go JSP/EJB for LAN applications or i can make them in core Java too.
No. They provide a framework, you can go lower and use RMI to call the server and build the server using normal classes. Or you could go lower still and open TCP sockets and send your data back and forth that way.
Alok sharma ji wrote: 2.if,its possible to create application like that in core java ,what kind of classes/packages i need for them(other then java.net) and 3rd party api's for simple working?
Yes. Easy as falling out of a tree. Write the classes you want and bang. I would suggest developing a first cut as a single process, with the business funtionality protected by a facade that only returns basic types. Then you can put the comms in the middle.
Alok sharma ji wrote: 3. how can such application be going to interact with each other or do i need threads (thread executions) to make it understand about every process going between diiferent client and one server?
I would suggest that you would want to handle each client on a seperate thread, otherwise you'll soon hit performance problems. Concurrency isn't magic, it is relativly easy to do.
Alok sharma ji wrote: 4. Is it not possible to achieve such facility with DB connection call with diff server ip/port instead of making the app to listen for its server and then work ?
I think the question here is about the backend data tier. You should use a JDBC defined connection then the DB can be configured at deployment. I would not expose the DB to the client.
Panic, Chaos, Destruction.
My work here is done.
or "Drink. Get drunk. Fall over." - P O'H
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thanks for your answers, on the point 4 i was thinking of passing the ip of DBserver (instead of passing a usual localhost) so the application connects itself their with no sweat, but i think thats a too much of wishful thinking 
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Anyone here doing any serious Android dev?
Should CP start a forum just for it?
Humble Programmer
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No i don't think we need a dedicated forum, after all it is just Java. Failing that you could always use the Mobile forum.
If you search the Articles for Android, you will find some others who are developing on the platform.
Dave
Find Me On: Web| Facebook| Twitter| LinkedIn
CPRepWatcher now available as Packaged Chrome Extension, visit my articles for link.
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I am trying to connect to oracle database installed in unix from java program using jdbc.
I get this error:
java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:164)
at Conn.main(Conn.java:6)
Exception in thread "main" java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getConnection(DriverManager.java:545)
at java.sql.DriverManager.getConnection(DriverManager.java:171)
at Conn.main(Conn.java:11)
I know I need to tell the path to the oracle driver, but I am not sure how to set it. I dont have a CLASSPATH environment variable. Do I need to create it? Please help
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itsh11 wrote: I dont have a CLASSPATH environment variable. Do I need to create it?
It would seem like a useful start. It's some time since I worked on UNIX but you just need to set a shell environment variable and export it; check the man pages for whichever shell you are using.
Just say 'NO' to evaluated arguments for diadic functions! Ash
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No, you do not need to set up the CLASSPATH environment variable, you can use the -classpath parameter when you run java, which is the way I always do it. I feel more "in control" when I set the classpath explicitly rather than relying on an environment variable which may or may not be right.
There are other ways to do it (e.g. put the driver jar into jre/lib/ext) but they can get a bit messy when you need to worry about different versions.
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i want to make a program that he can do this table:
can any one help me
to write code in j2me for this program
program :
1-add contact (mail).
2-record voice message (one minute).
3-send voice massege to contact.
please help.
the program connect to web server and send the message as mail
![Rose | [Rose]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/rose.gif)
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So here are some steps to do that:
1. Download Java SDK from Oracle
2. Install an IDE (Eclipse / Netbeans or whatever you like)
3. Read some about the Java ME
4. Start coding
And then when you encounter a specific issue or error post it here and we will help you allong.
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import java.util.*;
import java.text.*;
import javax.swing.*;
class Lab4Part2{
public static void main (String[] args) {
String ex1;
double sum, F, a=0, b=0;
JFrame myWindow=new JFrame();
myWindow.setSize(500,400);
myWindow.setTitle("Calculator");
myWindow.setVisible(true);
myWindow.setLocation(600,200);
ex1=JOptionPane.showInputDialog(myWindow, "Enter an expression");
F=Double.parseDouble(ex1);
sum=(a+B);
JOptionPane.showMessageDialog(myWindow, "The sum is "+sum);
}
}
I need some help I keep getting an error when I try to run it on JGrasp. I have no clue what I'm doing wrong and for that matter I don't know what I have to do next if I am doing something wrong or not. However I'm trying to create a program where there are one input dialog that asking for the expression in "a+b" form like I would have to input "1+2" and then the second dialog would be a message giving the answer to that 1+2 which would show the message of 3. The program compiles fun and runs fine however whenever it asks me in the input dialog for an expression and I put "5+15" the message dialog shows an answer of 0.0 which is wrong as it should be 20 or 20.0 so basically at this point I don't know what I'm doing wrong or what I should do next as I am only a freshman in college and is only taking beginners object oriented programming using Java but anyways Thanks for helping. One last thing, I asked my teacher what I should do and she said I should use the substring and indexOf methods but she never told me how so I'm curious to what I should do and I need help with this too please and thank you.
PS. I tried Double.parseDouble method however I realized I can't parse more than one variable therefore that wouldn't work.
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There's really a lot of things which are wrong with your code:
1) To calculate the sum, you add a and B, but they were never assigned any value except 0. And 0 + 0 is 0.
2) B doesn't exist, you declared b. So your program shouldn't even compile (I guess this is a typo error)
3) showInputDialog returns a string. You have to parse the string in order to extract the two values needed for the sum. But what if the user enters something else than a sum (like garbage text). You never check if the string is valid.
4) In fact you try to parse the string and store the result in F but it doesn't work this way: your string is not a double, because it contains a "+". So, first thing to do is to tokenize the string in order to retrieve the two operands.
Please, next time you have to post code, use the pre tags it makes the code much more readable (as explained in the posting guidelines that I suggest you to read).
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As explained above, let me make it a bit more clearer for you
import java.util.*;
import java.text.*;
import javax.swing.*;
class Lab4Part2{
public static void main (String[] args) {
String ex1;
double sum, F, a=0, b=0;
JFrame myWindow=new JFrame();
myWindow.setSize(500,400);
myWindow.setTitle("Calculator");
myWindow.setVisible(true);
myWindow.setLocation(600,200);
ex1=JOptionPane.showInputDialog(myWindow, "Enter an expression");
if(Pattern.compile("^\\d+[\\+]\\d+$").matcher(ex1).find()) {
String[] inputnums = ex1.split("+");
a = Double.parseDouble(inputnums[0]);
b = Double.parseDouble(inputnums[1]);
}
else
JOptionPane.showMessageDialog(myWindow, "The sum is "+sum);
}
}
--Modified the regex
I are n00b.
modified on Friday, October 8, 2010 12:08 PM
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obviously the //sum=a+b; is a typo, it should not be commented out
I are n00b.
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vivek886 wrote: Simple
Yep. So, what did you try?
CQ de W5ALT
Walt Fair, Jr., P. E.
Comport Computing
Specializing in Technical Engineering Software
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Actually i was asking the question
Q. Write a simple Java program to check whether input value is numeric or alphabet. If alphabet check whether its Capital or or lowwer case. If digit throw user defined exception " Digit not allowed."
Actually m new this forum and New to java. Can you please tell me the solution.
will be thank full to you.
Can this program be written in command line form?
Means if we run it from a command prompt.
or in AWT only.?
Sorry if any mistake from my side.
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vivek886 wrote: Simple
Do you mean that you could code this with your eyes closed, or you are throwing down a challenge to the rest of us?
Just say 'NO' to evaluated arguments for diadic functions! Ash
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Actually i was asking the question
Q. Write a simple Java program to check whether input value is numeric or alphabet. If alphabet check whether its Capital or or lowwer case. If digit throw user defined exception " Digit not allowed."
Actually m new this forum and New to java. Can you please tell me the solution.
will be thank full to you.
Can this program be written in command line form?
Means if we run it from a command prompt.
or in AWT only.?
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