[Solved] Access Problem with different classes and instances [modified] - Java Discussion Boards

rajivbirari3-Dec-09 21:52

3-Dec-09 21:52

hi , i want to develop an application in Java where one person will share screen with several people joining the conference , just need some help for start up. please share some links or help code to begin with.
I have no idea which technology i can use,how it's work flow.
Please anybody knows about that please help me.

Re: screen shairing application

Nagy Vilmos3-Dec-09 23:54

Nagy Vilmos

3-Dec-09 23:54

Have a read of the forums.

We will not do your work for you, but will happily help. Try, get stuck and THEN ask a question.

Panic, Chaos, Destruction.
My work here is done.

Re: screen shairing application

Arun Reginald Zaheeruddin1-Mar-10 0:05

Arun Reginald Zaheeruddin

1-Mar-10 0:05

You would need to look into the java.awt.Robot class to capture the screen. Just search for this class and you will get several tutorials explaining how to use it. But remember, this class just captures images of your desktop.

You would then have to send those images over the network to other computers using an implementation of either Datagram (UDP-based) or TCP-based Sockets or RMI.

Plus, also look into Serialization. These are the only pointers I can give you. People do not write tutorials about such stuff. I hope this helps you find a suitable direction to move forward in.

The beginning of knowledge is the fear of God

GWT https

sangeethanarayan3-Dec-09 17:36

sangeethanarayan

3-Dec-09 17:36

Is there any possible to create https page using GWT?

Re: GWT https

Nagy Vilmos4-Dec-09 0:24

Nagy Vilmos

4-Dec-09 0:24

sangeethanarayan wrote:
Is there any possible [way] to create https page using GWT?

Yes.

[Simple question gets a simple answer]

Panic, Chaos, Destruction.
My work here is done.

Re: GWT https

sangeethanarayan4-Dec-09 5:02

sangeethanarayan

4-Dec-09 5:02

I am new for GWT.Now i have application with http.but i want move the pages to https(ssl).how to implement this? Please explain that?

Re: GWT https

Nagy Vilmos4-Dec-09 5:34

Nagy Vilmos

4-Dec-09 5:34

Your original question wasn't at all clear. This is starting to move it out of the fog and into a light mist.

Let's start with the simple things:
0. What have you tried? [code example would be ggod]
1. Have you done a search? [bing.com is your friend here]

I am not an expert of intarweb stuff, but I'm pretty hot [well warm] on me java. My working knowledge would lead me to think that there will be an https class to do the hard work for you. Others may choose to do the search for you, I won't.

Panic, Chaos, Destruction.
My work here is done.

[Solved] Access Problem with different classes and instances [modified]

TheRainer3-Dec-09 16:13

TheRainer

3-Dec-09 16:13

Hello,

I am making a SWT application.
It consists of main-,tab-,table- and storage-classes with it's respective instances.
I got first "cannot make a static reference to a non-static method"-errors and then "No enclosing instance of the type XXX is accessible in scope"-errors.
At first my tab- and table-classes where with static methods an properties (first error messages appeared).
Trying to put the instances in public and/or static (global) variables brought the same errors.
Then I put everything into instances (second error messages appeared).

Actually I am runnnig the code from the main method through the instances:
...

GoalTrackerStorage GoalTrackerStorage = new GoalTrackerStorage();
GoalTrackerTabFolder GoalTrackerTabFolder = new GoalTrackerTabFolder();
GoalTrackerTable GoalTrackerTable = new GoalTrackerTable();

...

GoalTrackerTabFolder.createGoalTabFolder(display, shell);
GoalTrackerTable.createGoalTrackerTable(display, shell);

...

I tryed to load data from the storage instance into variables of the tab instance and got both type of errors, in the end only the second ones stayed.
I want to keep the storage-data within the storage-instance hence I want to manipulate the data within an object-array at runtime and multiple dimensional arrays can be defined extendable.

The storage class looks like this (just to give an idea, what I tried so far):

public class GoalTrackerStorage {
	public Object[][][][][][][][] dataObject;
	
	GoalTrackerStorage () {		
	dataObject = new Object [1][1][1][1][1][1][][];	
//	String typ = "Goal";
//	dataObject [0][0][0][0][0][0][0][0] = typ;
//	String goalName = "Goal Name";
//	dataObject [0][0][0][0][0][0][0][0] = goalName;
//	String posNeg = "positiv/negative";
//	dataObject [0][0][0][0][0][0][0][0] = posNeg;	
	}
}

So all this leads to my questions:
Is there a way to reach an instance from another instance?
Since I am no pro, what's the best way to store data of different types in a way one can add/remove or expand them at runtime in one place/object?

I am working since two weeks on the problem (nothing usable from google, the whole internet or books) and the project should complete next week! OMG | :OMG:

Thanks for help,
Rainer Roll eyes | :rolleyes:

modified on Friday, December 11, 2009 12:53 PM

modified on Wednesday, February 10, 2010 4:55 AM

Re: Access Problem with different classes and instances

Cedric Moonen3-Dec-09 23:40

Cedric Moonen

3-Dec-09 23:40

Your question is really vague but ir really looks like you are a bit confused about how to use classes properly.

TheRainer wrote:
Is there a way to reach an instance from another instance?

Yes, as long as the first object has access to the object it wants to use.

As far as I understood, you have a GoalTrackerStorage class which contains your data, and then you have other "GUI" classes that have to display the content of this class. Am I right ?
Well, the easy solution is to simply pass the instance of GoalTrackerStorage to your different classes that need to show it.

TheRainer wrote:
GoalTrackerStorage GoalTrackerStorage = new GoalTrackerStorage();
GoalTrackerTabFolder GoalTrackerTabFolder = new GoalTrackerTabFolder();
GoalTrackerTable GoalTrackerTable = new GoalTrackerTable();

By the way, this is wrong: you cannot have a class instance with the same name as a class. I suggest you use the standard notation in java: all the variables starts with a lowercase letter. So, you would write this instead:

GoalTrackerStorage goalTrackerStorage = new GoalTrackerStorage();
GoalTrackerTabFolder goalTrackerTabFolder = new GoalTrackerTabFolder();
GoalTrackerTable goalTrackerTable = new GoalTrackerTable();

So, in this case, the solution to your problem is to simply pass the goalTrackerStorage instance to the constructors of the different classes:

GoalTrackerStorage goalTrackerStorage = new GoalTrackerStorage();
GoalTrackerTabFolder goalTrackerTabFolder = new GoalTrackerTabFolder(goalTrackerStorage );
GoalTrackerTable goalTrackerTable = new GoalTrackerTable(goalTrackerStorage )

(Of course, you will need to supply a corresponding constructor to those classes).

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: Access Problem with different classes and instances [modified]

TheRainer11-Dec-09 4:33

TheRainer

11-Dec-09 4:33

@Cedric Moonen:

Thanks for the fast reply!

Yes, since I started using eclipse and java I somehow got into confusion (or is it just the "has to be done before christmas" syndrom of mine?)

I put your advice into code:

public class GoalTrackerMain {
	GoalTrackerMain () {
	}
	public static void main(String[] args) {
		GoalTrackerTabFolder goalTrackerTabFolderInstance = new GoalTrackerTabFolder(goalTrackerStorageInstance);
		GoalTrackerTable goalTrackerTableInstance = new GoalTrackerTable(goalTrackerStorageInstance);

...

public class GoalTrackerTabFolder {
	GoalTrackerTabFolder () {
	}
	GoalTrackerTabFolder (GoalTrackerStorage goalTrackerStorageInstance) {
		GoalTrackerStorage goalTrackerStorageInstanceTemp = goalTrackerStorageInstance;
	}
	public void createGoalTabFolder (Display display, Shell shell) {
		goalTrackerStorageInstanceTemp.??? <-- Error:goalTrackerStorageInstanceTemp cannot be resolved to a type
		...
	}

...

public class GoalTrackerTable {
	}
	GoalTrackerTable (GoalTrackerStorage goalTrackerStorageInstance) {
		GoalTrackerStorage goalTrackerStorageInstanceTemp = goalTrackerStorageInstance;
	}
	public void createGoalTrackerTable (Display display, Shell shell) {
	...
	}

So I proceeded, but I am now stucked up at the "goalTrackerStorageInstanceTemp cannot be resolved to a type"-error indicated above in the class GoalTrackerTabFolder. OMG | :OMG:

Any further helpfull ideas/tipps? Confused | :confused:

Thanks in advance,
Rainer

modified on Friday, December 11, 2009 12:54 PM

Re: Access Problem with different classes and instances

Cedric Moonen11-Dec-09 4:43

Cedric Moonen

11-Dec-09 4:43

I think you should really start learning the basics. This is really really basic java programming. You pass the variable in the constructor but you only store it in a local variable in your constructor. Which means that it is not visible outside that method. You have to make it a member variable of your class in order for it to be accessible in other methods.

Please use the code block tag when posting code, because it is very difficult to read otherwise.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: Access Problem with different classes and instances

TheRainer11-Dec-09 7:05

TheRainer

11-Dec-09 7:05

Thanks Cedric, that brought the final solution for me. Big Grin | :-D

And yes, my basics seem to be thin.
I only wonder why I don't get such points when I read my books about java:
- Go To Java 2, 2. Auflage . Handbuch der Java-Programmierung von Guido Krüger von Addison-Wesley
- JAVA als erste Programmiersprache. - vom Einsteiger zum Profi von Joachim Goll, Cornelia Weiß, und Frank Müller von B.G. Teubner Verlag

Finding a usefull book is not such easy. D'Oh! | :doh:

Back Button on popup window doesn't work in IE

sam#2-Dec-09 0:46

sam#

2-Dec-09 0:46

Hi! I created a page that has a "Back Button", it opens up as a pop up window. The Back Button doesn't work IE but id does in FireFox Mozilla.
I have tried with window.history.go and window.history.back but non of them is working. Any Suggestion please ?

Re: Back Button on popup window doesn't work in IE

David Skelly2-Dec-09 0:55

David Skelly

2-Dec-09 0:55

Wrong forum. This is not a Java question. You will have more luck with this if you post it in the Web Development forum.

Output error for Avl tree

vtsmokey881-Dec-09 19:14

vtsmokey88

1-Dec-09 19:14

The fact thats it an AVL tree probably doesn't matter. I have a printTree method in my tree class and I'm trying to print the nodes in the form of the tree. I've successfully printed the nodes the correct way but now I'm trying to label the nodes by their relative height (i.e. equalheight, right hi, left hi).

The problem is my root, which is right hi, won't change to that. Everything else is working for every node except the root, but the counter I made that determines the label is the right number. I can't for the life of me figure out why it is staying at equal height.

The first thing is the label, then the node, and the end number is the count.

EDIT: I know you can't tell because the tabs got taken out but alstoto01 is the root, thus the first node to go through the methods.

This is what I'm outputting right now (the Wrong way):
EQUALHT:aaronha01: 0
EQUALHT:agganha01: 0
EQUALHT:alliega01: 0
EQUALHT:alstoto01: -1
EQUALHT:bollifr01: 0
EQUALHT:cronera01: 0
EQUALHT:grammal01: 0
EQUALHT:henlega01: 0
RIGHTHI:herrito01: -1
EQUALHT:jacobsp01: 0

The Correct output should be:
EQUALHT:aaronha01: 0
EQUALHT:agganha01: 0
EQUALHT:alliega01: 0
RIGHTHI:alstoto01: -1
EQUALHT:bollifr01: 0
EQUALHT:cronera01: 0
EQUALHT:grammal01: 0
EQUALHT:henlega01: 0
RIGHTHI:herrito01: -1
EQUALHT:jacobsp01: 0

Here is the code for the printTree method:

private ArrayList<AnyType> printTree( AvlNode<AnyType> t, String buffer )
    {
        if( t != null )
        {
        	int count = counter(t);
            if(count == 0)
            	freq = "EQUALHT:";
            if(count < 0)
            	freq = "RIGHTHI:";
            else if(count > 0)
            	freq = "LEFTHI:";

        	printTree( t.left, buffer + "   ");
            pTree.add((AnyType) (buffer + freq + t.element + ":") );
            System.out.println(buffer + freq + t.element + ":" + count);
            printTree( t.right, buffer + "   ");
            return pTree;
        }
        return null;
    }

Here is the code for my counter method:

private int counter(AvlNode<AnyType> t){
    	int count = 0, left = 0, right = 0;
    	AvlNode<AnyType> temp = t;
    	while(temp != null){
    		temp = temp.right;
    		right++;
    	}
    	while(t != null){
    		t = t.left;
    		left++;
    	}
    	count = left - right;
    	return count;
    }

It's probably a simple fix but I just can't see it. Any help would be appreciated since this is a really stupid problem to have in the grand scheme of things.

Re: Output error for Avl tree

vtsmokey881-Dec-09 20:04

vtsmokey88

1-Dec-09 20:04

Never mind, it was a simple fix. Just needed to bring my freq variable down into the method.

private ArrayList printTree( AvlNode t, String buffer )
    {
        if( t != null )
        {
        	int count = counter(t);
                String freq = "";
            if(count == 0)
            	freq = "EQUALHT:";
            if(count < 0)
            	freq = "RIGHTHI:";
            else if(count > 0)
            	freq = "LEFTHI:";

        	printTree( t.left, buffer + "   ");
            pTree.add((AnyType) (buffer + freq + t.element + ":") );
            System.out.println(buffer + freq + t.element + ":" + count);
            printTree( t.right, buffer + "   ");
            return pTree;
        }
        return null;
    }

Re: Output error for Avl tree

Nagy Vilmos1-Dec-09 21:40

Nagy Vilmos

1-Dec-09 21:40

You get an up tick for showing us your answer and not doing just deleting the question. Have a Beer | [beer]

Panic, Chaos, Destruction.
My work here is done.

Bakhshali Approximation for finding the square root of a number..?

silentbob03211-Dec-09 14:27

silentbob0321

1-Dec-09 14:27

Can anyone get this to work?

Goal: This program will implement Bakhshali Approximation for finding the square root of a number. The algorithm to approximate the square root of N is

1. Start with the initial approximation of 1.
2. As long as the approximation isn’t close enough, use a while loop to repeatedly refine the approximation using the following formulas

d = N – (initial approximation)^2
P = d/(2 * initial approximation)
A = initial approximation + P
new approximation = A - P^2/(2*A)

(What does “close enough” mean? For your program, you’ll take close enough to mean that )
∣newApproximation-oldApproximation∣<. 0001∗N)
Other features:

If the user types a negative number, he/she should be alerted that only nonnegative numbers are acceptable.
Your program should correctly compute the square root of 0, which is 0.
There should be a Clear button to clear both the text box and textarea.

Any help with be greatly appreciated!!

Re: Bakhshali Approximation for finding the square root of a number..?

Nagy Vilmos1-Dec-09 21:47

Nagy Vilmos

1-Dec-09 21:47

silentbob0321 wrote:
1. Start with the initial approximation of 1.
2. As long as the approximation isn’t close enough, use a while loop to repeatedly refine the approximation using the following formulas

d = N – (initial approximation)^2
P = d/(2 * initial approximation)
A = initial approximation + P
new approximation = A - P^2/(2*A)

Contains the answer to your homework. We don't do homework, we'll help but not just do it for you.

This is basic for any language, if you cannot do it either your tutor is stupid for not being able to explain the concepts or you are for not understanding. The only other advice I can give you is to practice the phrase "You want fries with that?"; you'll need it when you start working.

Panic, Chaos, Destruction.
My work here is done.

Re: Bakhshali Approximation for finding the square root of a number..?

Richard MacCutchan1-Dec-09 21:48

Richard MacCutchan

1-Dec-09 21:48

silentbob0321 wrote:
Can anyone get this to work?

Yes, but since this is your homework it is up to you to at least try. You have even been given the algorithm for your solution so it's just a simple matter of writing the java statements to implement that algorithm.

How to make Swing GUI stable in GridBagLayout

don Moen30-Nov-09 19:20

don Moen

30-Nov-09 19:20

Hello all,

I have 5 textareas one below the another. They are packed using the GridBagLayout (Doing all this in NetBeans 6.5). When only one line text is fetched in the textarea everything is fine, but the moment the text fetched is of 2 or more lines, all the textareas size increases reducing the last panel's (below 5 textares) height.

This also happens with the combo box. when the items fetched are greater than the width of the combo its width increases and comes to normal if the items are of less width.

Anybody faced such problem ??? Plz. help.

Re: How to make Swing GUI stable in GridBagLayout [modified]

LunaticFringe2-Dec-09 2:45

LunaticFringe

2-Dec-09 2:45

You will probably need to develop a custom layout manager rather than using one of the pre-defined layout modes. Basically, you create a class that implements LayoutManager, providing an implementation for the layoutContainer method, among others. You then instantiate your manager and assign it to be the parent window's manager with setLayout.

Try plowing through the docs for LayoutManager and take a whack at it. I can help if you have trouble.

[edit]
Hint - If you make your custom layout manager an inner class of the parent window, it'll have access to the control variables representing the text areas and be able to manipulate their positions.
[/edit]

modified on Wednesday, December 2, 2009 1:02 PM

Re: How to make Swing GUI stable in GridBagLayout

don Moen2-Dec-09 19:57

don Moen

2-Dec-09 19:57

thanks ....

will get back to u, when i start working on that.
currently working on other higher priority issues.

thanks again..

java effects

ammu2328-Nov-09 5:23

ammu23

28-Nov-09 5:23

Is it advanced concept?what is java effects?Where can i use it?Please give any url for java effects tutorial..

vinoli

Re: java effects

Richard MacCutchan28-Nov-09 5:52

Richard MacCutchan

28-Nov-09 5:52

Why not try this[^] first!

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.