Declaring Static Variables

Is it a bad way to declare somany Static Variables in a program?
-Achyuth B

ok..
So if in a swings program if i am using only one frame through out the program, by adding and deleting components on it.
Then i can declare that frame as Static, right.
So that i can call the same frame(and not instance of it) from different class.
And if i have to take the value entered in a JTextField from another class, Then that JTextField can also be declared as Static right.
-Achyuth B

Similar Messages

Declaring static variable in JSP

<%
static Logger browserDetectLog = Logger.getLogger(ScoConstants.LOGGER_BROWSERDETECT);
%>
I m declaring the logger variable like dis.
It gives me error, whereas in java class it does'nt.
Please tell me the difference.

Anything in <% %> delimiters is put inline.
Anything in <%= %> is put inline but without closing the current out.print().
Anything in <%! %> is put outside of the _jspservice() method.You should be doing
<%!
static Logger browserDetectLog = Logger.getLogger(ScoConstants.LOGGER_BROWSERDETECT);
%>

Declaring static variable to save memory, memory cost of link

If I have plenty of objects of the same class and they have a field that is the same for all objects, do I save memory by declaring it 'static'?
How much memory is used by an object to store a link that points to another object?
/Carlis

Ok!
I am making a map for a computer game, and it has plenty of Towns. Now, every object of type 'Town' has a list with different Tribes
String[] Tribes= {"Roman", "Teuton", "Gaul"};
This list is identical for all objects of type 'Town'.
Now, if I declare it to be static like this;
static String[] Tribes={...};
Does this save memory? If I understand this correctly, the 'static' keyword means that the 'String[] Tribes' is only stored once rather than in every object of type 'Town'.

Can't we declare a static variable inside a memberfunction of a class?

Hi,
class A{
public void fun()
static int i=10;
can' we declare static variable in member function of class?
Thanks,

It is a common idiom in C and C++, but it is forbidden
in Java because it adds hidden dependencies.
The C way of writing a serial number generator:
int generate() {
static int n = 0;
return n++;
}Pure C has only global functions. So it needs inner
static variables to help to hide the data. I've had
lots of headaches trying to make C programs with inner
static variables work correctly because they usually
are hidden in cross-reference listings.
The Java way:
public static class SerialNumberGenerator() {
private static int n = 0;
public static int generate() {
return n++;
}The code above is as static as the C code given
before, but it tries to be more explicit (no hidden
variables).Hum... have you tried to compile your sample ?
(And anyway, what the hell would a static class be used for ???)
But perhaps you meant:
public final class SerialNumberGenerator {
   private static int n = 0;
   public static int generate() {
      return n++;

Static variable in session bean

Can we declare static variable in session bean. If we declare what will happen. Will it create error in compile time or not deployed in server.

From a Java language perspective, nothing stops you from declaring a static variable in a session
bean class. It will compile as long as its syntactically correct.
From an EJB programming model perspective, the use of non-final static variables
is discouraged because it breaks the JVM-transparency that is an important aspect of the
EJB architecture. It should be possible to deploy a single EJB application to a cluster and
have it behave exactly as if it were deployed to only one server instance (albeit with higher
overall throughput/performance). Using non-final static variables breaks this property
because the bean instances in one JVM will see a different value for the static variable
than bean instances in a different JVM.
It also forces you to deal with synchronization
of the shared data, which is a complexity that was carefully avoided in the EJB programming
model by ensuring that each bean instance is single-threaded.
Bottom line is you can have "final static" data members in EJB classes but you should
avoid non-final (mutable) static data.
--ken

Using a static variable declared in an applet in another class

Hi guys,
I created an applet and i want to use one of the static variables declared in teh applet class in another class i have. however i get an error when i try to do that...
in my Return2 class i try to call the variable infoPanel (declared as a static JPanel in myApplet...myApplet is set up like so:
public class myApplet extends JApplet implements ActionListener, ListSelectionListener
here are some of the lines causing a problem in the Return2 class:
myApplet.infoPanel.removeAll();
myApplet.infoPanel.add(functionForm2.smgframeold);
myApplet.infoPanel.validate();
myApplet.infoPanel.repaint();
here are some of the errors i get
dummy/Return2.java [211:1] package myApplet does not exist
myApplet.infoPanel.removeAll();
^
dummy/Return2.java [212:1] package myApplet does not exist
myApplet.infoPanel.add(functionForm2.smgframeold);
^
dummy/Return2.java [213:1] package myApplet does not exist
myApplet.infoPanel.validate();
^
dummy/Return2.java [214:1] package myApplet does not exist
myApplet.infoPanel.repaint();
^
please help! thanks :)

I don't declare any packages though....i think it just doesn't recognize myApplet for some reason..
other errors i got compiling are:
dummy/Return2.java [82:1] cannot resolve symbol
symbol : variable myApplet
location: class Return2
updateDesc.setString(3, myApplet.staticName);
I Don't get why i'm getting this error cuase they worked fine when myApplet was a standalone application, not an applet.
myApplet is in the same folder as Return2 and it compiles properly.

Static variable declaration in JavaFX

Hello, I'd like to ask how to substitute static key word to declare a variable, that is visible within the current package and accessible without creating an instance of a class, that contains this variable. Because my NetBeans insists that static variable is depricated.
Thank you.

In Foo.fx...
class Foo {
// bar is an instance variable that has public access
public def bar = "bar";
// baz is a "static" variable that has public access
public def baz = "baz";
// someFun is a "static" function
public function someFun() : Void {
}In Main.fx...
println("{Foo.bar}"); // compile error - cannot reference bar from static context
println("{Foo.baz}"); // This is ok - Foo.baz is static
var foo = Foo{}
println("{foo.bar}"); // This is ok. bar referenced from Foo instance

Clarification about static variables declaration

I'm getting "Illegal Start of Expression" error, When i try to declare a static variable within a static metho or nonstatic method.
Could you please clarify me,
Is it possible to declare a static varible within a static method or non static method ?
Thanks

Hi Vikas,
First, note that this forum is devoted to Sun Java Studio Creator IDE. General Java questions can be asked on forums here: http://forum.java.sun.com/
Second, note that static variable can be defined only as member of class. It cannot be defined inside of method.
Thanks, Misha
(Creator team)

Declare a variable in an Interface

hi all
can i declare a variable in a interface , something like
public static final String dsn=" // something";
so that i dont have to declare the same thing in all the classes that implement this interface
regards

You don't need the public, static, or final. All fields in interfaces are implictly public static final fields.

Using Static Variable against Context Attribute for Holding IWDView

Dear Friends,
I have a method which is in another DC which has a parameter of the type IWDView. In my view, I will have an action which will call the method in another component by passing the value for the view parameter. Here, I can achieve this in 2 types. One is - I declare a static variable and assign the wdDoModifyView's view as parameter value and I can pass this variable as parameter whenever calling that method or the second way - create an attribute and assign the same wdDoModifyView's view parameter as its value. Whenever I call this method, I can pass this attribute as parameter. What is the difference between these two types of holding the value since I am storing the same value i.e., wdDoModifyView's view parameter. But when I trigger the action from different user sessions, the first type of code (using static variable) prints the same value in both the sessions for view.hashCode() and View.toString(), but the same is printing the different values when I pass the attribute which holds the view parameter.
Clarification on this is highly appreciated
The problem I face is when I use static variable to get the view instance and export the data using the UI element's id, the data belonging to different user sessions is mixed up where as when I use Context Attribute, the same problem doesn't arise. I want to know the reason why it is so. Is there any other place or way where I can get the current view instance of each session instead of wdDoModifyView?

Hi Sujai ,
As you have specified the problem that we face when we use static attributes, when end users are using the application .
Static means i have n number of objects but the static variable value will remain same every where.
when it is context attribute for every object i.e nth object you have a nth context attribute i mean nth copy of the context attribute.
so every user has a unique Iview parameter , when context is used and
when static is used , assume you have userA , his iview is set this intially and u have another user B , when he is using , since the variable is static and when you access this variable you will get the value of userA.
Regards
Govardan Raj

How to give different value to a static variable???

Hi all:
Is there any solution to set different values to a static variable???I had try two ways but all have errors!
1.Way_1
protected String tmp=null;
protected void initSituation(int sayorpress)
if (sayorpress==0)
tmp = "string1";
else if (sayorpress==1)
tmp = "string2";
protected static String RESOURCE_STRING = tmp; <---error
Error:non-static variable tmp cannot be referenced from a static context
2.Way_2
protected void initSituation(int sayorpress)
if (sayorpress==0)
protected static String RESOURCE_STRING = "string1"; <---error
else if (sayorpress==1)
protected static String RESOURCE_STRING = "string2"; <---error
Error:illegal start of expression at
not an expression statement at
Thank you very mich!!!

Try this:
protected static String RESOURCE_STRING = null;
protected void initSituation(int sayorpress)
if (sayorpress==0)
yourClass.RESOURCE_STRING = "string1";
else if (sayorpress==1)
yourClass.RESOURCE_STRING = "string2";
You cannot declare a static variable inside a method. But you can access a static variable thorugh your class.

To use a static variable in another class,but report NullPointerException

when TableMain is running,I run testRecord so that let TableMain add a occur informatin and
happened time in a row in TableMain,but when I run testRecord,java report a NullPointerException and I dont know how to solve this problem,thanks for helping me to check my code;(error report info is in end)
import java.awt.event.*;
import javax.swing.table.*;
import java.io.*;
public class TableMain extends JFrame{
JTable table;
static OwnModel model;
String[] columnHeader={"occur","time"};
class OwnModel extends DefaultTableModel{
public OwnModel(Object[] columnNames,int numRows){
super(columnNames,numRows);
public boolean isCellEditable(int row,int column){
return false;
public TableMain(){
model=new OwnModel(columnHeader,0);
table=new JTable(model);
JScrollPane scroll=new JScrollPane(table);
JButton save=new JButton("save record");
JButton delete=new JButton("delete record");
JPanel buttons=new JPanel();
buttons.add(save);
buttons.add(delete);
JLabel sign=new JLabel("occur record");
Container cp=getContentPane();
cp.add(BorderLayout.NORTH,sign);
cp.add(BorderLayout.CENTER,scroll);
cp.add(BorderLayout.SOUTH,buttons);
this.setSize(300,500);
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
public static void main(String[] args){
new TableMain();
import java.util.Vector;
import java.util.Calendar;
import java.text.SimpleDateFormat;
public class testRecord{
public static void main(String[] args){
SimpleDateFormat simpledf=new SimpleDateFormat("yyyy/MM/dd hh:mm:ss");
String tableName="friends";
Calendar occurtime=Calendar.getInstance();
Vector record=new Vector();
record.add("send 'desc' sql, "+"operated table is :"+tableName);
record.add(simpledf.format(occurtime.getTime()));
System.out.println("model is "+Guide.model);
System.out.println("record is "+record);
Guide.model.addRow(record);
error report:
model is null
record is [send 'desc' sql,operated table is :friends, 2004/05/26 11:39:03]
Exception in thread "main" java.lang.NullPointerException
at testRecord.main(testRecord.java:14)

but I just use this constructor once,never use twice
with same jvm;I thinks my idea is not too very badIt's a public constructor (if I'm looking in the right
place) - it could be called from anywhere. To
intialize a static variable outside the declaration,
use a static initializer:private static String whatever;static {
whatever = "whatever";
}Or simply (in this case):private static String whatever = "whatever";

Static Variable in webapplication

Are the values of static variables preserved when two different users try and access them? i.e.
If one web application user sitting in Chicago sets a static variable to 'true' from 'false'. Will the other user sitting in Omaha see it as 'true' or 'false' in his session?

Alright, I did this test.
1) On my local tomcat I created a mini webapp where I
declared a static which populates from a form field.
static String displayname = "";
displayname = request.getParameter("username");
and then displayed it on the html page.
2) I opened IE sessions of my application and in one
I gave the user name 'Tom' and other 'Janet' and hit
continue. (Tom before Janet)
3) The page that had 'Tom' displayed tom and other
one Janet. Then I refreshed the display page for the
tom instance and it still showed 'Tom'.
Conclusion: It appears that the statics are indeed
loyal to the class loader and not the JVM. Hence, for
multiple users each instance should have its own
static.
Please let me know if you disagree or see my test to
be wrong.
Thanks
Message was edited by:
Birthdayhitting the refesh button on your IE page doesn't show you what the value of the static variable in your web app is. You're headding for trouble.
EDIT: Ok well it depends on you implementation how the refresh will work, but if you have a static fields in a class on your web server I promise you it's not in any way associated with any session.

How to declare class variable with generic parameters?

I've got a class that declares a type parameter T. I know how to declare a static method, but this doesn't work for a static variable:
public class Test< T >
    * Map of String to instances of T.
    * error: '(' expected (pointing to =)
    * <identifier> expected (pointing to () )
   private final static < T > Map< String, T > MAP = new HashMap< String, T >();
    * Get instance of type T associated with the given key.
   public final static < T > T getType( String key )
      return MAP.get( key );
}Edited by: 845859 on Mar 20, 2011 11:46 AM

jveritas wrote:
I'm trying to create a generic polymorphic Factory class that contains boilerplate code.
I don't want to have to rewrite the registration code every time I have a different return type and parameter.I haven't seen a case yet where that is reasonable.
If you have hundreds of factories then something is wrong with your code, design and architecture.
If you have a factory which requires large number of a varying input types (producing different types) then something is probably wrong with your code and design.
A reasonable factory usage is one where you have say 20 classes to be created and you need to add a new class every 3 months. Along with additional functionality represented by the class itself and perhaps variances in usage. Thus adding about 3 lines of code to one class is trivial. Conversely if you have hundreds of classes to be created by the factory and you are adding them daily then it is likely that
1. Something is wrong with the architecture which requires a new class every day.
2. You should be using a dynamic mechanism for creation rather than static because you can't roll out a static update that often.
More than that the idiom that leads to factory creation is different for each factory. A factory that creates a database connection is substantially different than the one used in dynamic rules logic processing. A generic version will not be suitable for both.
Actualy the only case I know of where such a factory might be seem to be a 'good' idea is where someone has gotten it into their head that every class should be represented by an interface and every class created by a factory (its own factory.) And of course that is flawed.

Non-static variable cant accessed from the static context..your suggestion

Once again stuck in my own thinking, As per my knowledge there is a general error in java.
i.e. 'Non-static variable cant accessed from static context....'
Now the thing is that, When we are declaring any variables(non-static) and trying to access it within the same method, Its working perfectly fine.
i.e.
public class trial{
�� public static void main(String ar[]){ ////static context
�� int counter=0; ///Non static variable
�� for(;counter<10;) {
�� counter++;
�� System.out.println("Value of counter = " + counter) ; ///working fine
�� }
�� }
Now the question is that if we are trying to declare a variable out-side the method (Non-static) , Then we defenately face the error' Non-static varialble can't accessed from the static context', BUT here within the static context we declared the non-static variable and accessed it perfectly.
Please give your valuable suggestions.
Thanks,
Jeff

Once again stuck in my own thinking, As per my
knowledge there is a general error in java.
i.e. 'Non-static variable cant accessed from static
context....'
Now the thing is that, When we are declaring any
variables(non-static) and trying to access it within
the same method, Its working perfectly fine.
i.e.
public class trial{
�� public static void
main(String ar[]){ ////static context
�� int counter=0; ///Non
static variable
�� for(;counter<10;) {
�� counter++;
��
System.out.println("Value
of counter = " + counter) ; ///working fine
�� }
�� }
w the question is that if we are trying to declare a
variable out-side the method (Non-static) , Then we
defenately face the error' Non-static varialble can't
accessed from the static context', BUT here within
the static context we declared the non-static
variable and accessed it perfectly.
Please give your valuable suggestions.
Thanks,
JeffHi,
You are declaring a variable inside a static method,
that means you are opening a static scope... i.e. static block internally...
whatever the variable you declare inside a static block... will be static by default, even if you didn't add static while declaring...
But if you put ... it will be considered as redundant by compiler.
More over, static context does not get "this" pointer...
that's the reason we refer to any non-static variables declared outside of any methods... by creating an object... this gives "this" pointer to static method controller.

Declaring Static Variables

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