Static variables after destroyApp()

it seems that classes rest in the kvm after the termination of a midlet.
when i restart the midlet the values of static variables rest. Is there a good reason for this? To me it seems a big source of bugs.
e.g.:
public class AClass {
private static int value= 0;
public static void setValue(int val){
value= val;
public static int getValue(){
return value;
public class StaticTest extends javax.microedition.midlet.MIDlet {
public void startApp() {
System.out.println(AClass.getValue());
AClass.setValue(10);
System.out.println(AClass.getValue());
destroyApp(false);
notifyDestroyed();
public void pauseApp() {
public void destroyApp(boolean unconditional) {
}

I think you will have to explicitly set the static variable to null at destroyApp(). Run with a profiler and you should see the difference.

Similar Messages

Error on compile - non-static variable can not be referencedfrom static con

Error on compile happening with addButton?
Thanks
import java.awt.*;
import java.awt.event.*;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JFrame;
public class Log implements ActionListener {
JButton addButton;
public static void addComponentsToPane(Container pane) {
pane.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
     c.gridy = 3;
c.gridx = 0;
     JLabel callsignLabel= new JLabel("Callsign");
pane.add(callsignLabel, c);
     c.gridy = 3;
c.gridx = 1;
     JLabel nameLabel= new JLabel("Name");
pane.add(nameLabel, c);
     c.gridy = 3;
c.gridx = 2;
     JLabel timeLabel= new JLabel("Time");
pane.add(timeLabel, c);
     c.gridy = 3;
c.gridx = 3;
     JLabel dateLabel= new JLabel("Date");
pane.add(dateLabel, c);
     c.gridy = 3;
c.gridx = 4;
     JLabel frequencyLabel= new JLabel("Freq ");
pane.add(frequencyLabel, c);
     c.gridy = 3;
c.gridx = 5;
     JLabel locationLabel = new JLabel("Country/State");
pane.add(locationLabel, c);
c.gridy = 5;
c.gridx = 0;
     addButton = new JButton("Add");
pane.add(addButton, c);
     addButton.addActionListener(this);

Thank you for the reply
I am new to Java
What is wrong with the way it is coded?The error message tells you what's wrong: You're trying to reference a non-static variable from a static context.
If you don't know what that means, then click the link I provided and look at the results from that google search. You might have to go through a few before you find a satisfactory explanation. And after you've done that, if you have specific questions about things you didn't understand there, please post again.

Non static variable errors

I have been working on this file for 4 days now and I can't get past these errors.
Here's the whole project:
package toysmanager;
public class ToysManager {
//Method ToysManager
public ToysManager() {
//Method main
public static void main(String[] args) {
ToddlerToy Train1 = new ToddlerToy();
ToddlerToy Train2 = new ToddlerToy();
ToddlerToy Train3 = new ToddlerToy();
System.out.print("This is an object of type ToysManager");
Train1.PrintProductID();
Train2.PrintProductID();
Train3.PrintProductID();
public class ToddlerToy{
private int ProductID = 0;
private String ProductName = "";
private float ProductPrice = 0;
public ToddlerToy(int id,String name, float price){
ProductID = id;
ProductName = name;
ProductPrice = price;
//Method PrintProductID
public int PrintProductID(){
System.out.print("This method is PrintProductID in the class ToddlerToy");
System.out.print("Product ID is:" + ProductID);
return ProductID;
public String PrintProductName(){
System.out.print("This method is PrintProductName in the class ToddlerToy");
System.out.print("Product Name:" + ProductName);
return ProductName;
public float PrintProductPrice(){
System.out.print("This method is PrintProductPrice in the class ToddlerToy");
System.out.print("Product Price: $" + ProductPrice);
return ProductPrice;
And here are the errors:
"ToysManager.java": non-static variable this cannot be referenced from a static context at line 9, column 29
"ToysManager.java": ToddlerToy(int,java.lang.String,float) in toysmanager.ToysManager.ToddlerToy cannot be applied to () at line 9, column 29
"ToysManager.java": non-static variable this cannot be referenced from a static context at line 10, column 29
"ToysManager.java": ToddlerToy(int,java.lang.String,float) in toysmanager.ToysManager.ToddlerToy cannot be applied to () at line 10, column 29
"ToysManager.java": non-static variable this cannot be referenced from a static context at line 11, column 29
"ToysManager.java": ToddlerToy(int,java.lang.String,float) in toysmanager.ToysManager.ToddlerToy cannot be applied to () at line 11, column 29
Any help would be appreciated as I am plainly not understanding this even with a book.

Annie:
Could you help me understand the original ToyManager instructions more please? Not asking you to do the work for me I just do not understand exactly what they want me to do...
Assignment:
After you install JCreator, write a Java program, with a single class called ToysManager. The main method should print the name of the class, for example: "This is an object of type ToysManager."
(Hint: the process is very similar to the "Hello World!" program.)
Please add file (.java)
Group Portion:
Deliverables: two *.java files
As a group, add a second class called ToddlerToy to your ToysManager project.
Here are the requirements for the ToddlerToy:
    * The class ToddlerToy is public and has a default constructor.
    * It has one private attribute called ProductID (of type int).
    * It has two public methods called SetProductId() and PrintProductId().
    * The method SetProductId() assigns a value to the attribute ProductId. For now, the value is hard-coded.
    * The method PrintProductId prints the value of the attribute ProductId.
    * The class ToddlerToy has no main() method. In Java, there is only one main method for the entire program. In this case, the main method is in the ToysManager class.
Here are the requirements for the main method of the ToysManager class:
    * Create an object called Train1 of class type ToddlerToy, using the default constructor.
    * Call the methods SetProductId() and PrintProductId() to set then print the the value of ProductId.
    * The first statement in each method should print the name of the method, for example: "This is method <method name> in class <class name>". This should help you trace the execution of your program. Feel free to comment out the print statement.
    * On the Small Group Discussion Board, discuss your understanding of the concepts of class, object, constructor, method, and attribute.
    * Give one example of a class (giving its name, attributes, and methods) that could be part of the shipping application.ANY help with this at all is greatly appreciated...a friend of mine found your post and used it to give me code snippets for help and I had no idea. Nearly got me in deep water...redoing the assignment but personally I find the next two assignments much easier to understand than this one. The instructions are confusing to me...can you point me in the right direction?

Alternatives to binding to static variables

As has been discussed before, flex does not dispatch a binding event when a static variable changes. I was wondering if there are any alternatives to simulate this functionality.
I have a class called UserDataManager which contains static properties i use throughout my application. One of these is an array which i need to access and change on various different components throughout my application. After changing this must then change the array on all the other components.
I suspect i could manage this by 2-way binding on an instance of UserDataManager and passing this instance to all the components on creation, however this seems like a computationly and time expensive workaround.
Are there any alternatives?
Thanks

Use a singleton pattern so your statics arent static.

Value of x , static variable..

In the method callMe() i am returning x , which is 0, that gets assigned to x in main(the same static variable), then i am incrementing x. But the value of x is 0.
Whats happening.
public class TestClass {
     static int x=0;
     static int callMe(){
          return x++;
     public static void main(String[] args) {
          x = callMe();
          System.out.print("x= "+ x);
}

In the method callMe() i am returning x , which is 0,
that gets assigned to x in main(the same static
variable), then i am incrementing x. But the value of
x is 0.
Whats happening.
public class TestClass {
     static int x=0;
     static int callMe(){
          return x++;
     public static void main(String[] args) {
          x = callMe();
          System.out.print("x= "+ x);
syntax subtletly... i++ and ++i both do the same thing : increment 'i', but...
i++ // value : i BEFORE incrementation
++i // value : i AFTER incrementationabundantly documented and answered on this forum, next time, use the search button ;-)
hth

Equivalent of visual Basic static variable in LabVIEW

Hi all!
I am doing a project where I am counting the values. After i Close/Stop the program I want the value to be intact and continue with the last value.
I know this in Visual Basic. By using the Static variable we can retain the value even we close the program.
Kindly help..
Srikanth Chilivery,
Solved!
Go to Solution.

I have trouble believing that a static variable retains its value after the program is terminated. Once the program is released from memory, that static variable is gone. If you want to retain a value between closing and opening an application, you have to save it to disk in some way.
Are you working exclusively in the LabVIEW IDE or are you running EXEs? It sounds like you probably just want to use a Functional Global Variable/Action Engine.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Is is better to use static variables?

Hi,
Does anyone know if it's better to use static variables or to use normal variables?
Concerning the size of the code, it seems that declaring a variable as static is more consuming (for example plus 6 bytes for an object reference).
So this could mean that declaring variables as static should be avoided, but what about the execution time?
Some years ago, some javacard gurus were claiming that it's was better to use static variables (less processing required by the JVM to resolve adresses of static variables), but is it still the case?

Hi Lexdabear,
Thanks for the answer.
I did the test (I converted my all code to use static variables and methods as much as possible), and did a bench before and after, on a JCOP31 card.
The conclusion is that today JVMs and processors are much powerful than 5 years ago, and that the difference is really difficult to measure, which anyway is a good thing for us ;-)

Static variables at runtime

dear friends
how to delete the static variables and objects after using them ?

What do you mean with "delete static variables and objects"?
You know you cannot explicitly delete objects in Java, that's why there is garbage collection. And you cannot force garbage collection to happen. The only thing you can do is make an object eligible for garbage collection by removing all references to the object. You can do this by for example setting your static reference to null:
public class Demo {
static Integer thingy = new Integer(9567412);
void demo() {
// Set thingy to null, so that the object it refers to may be garbage collected
thingy = null;
}Jesper

Static variable gets cached

HI,
I'm having trouble with a java servlet's static variable. I have a jsp page which calls a java servlet. Inside the servlet, I have a global varialbe that I'm using to store information in, however this variable must not be initialized unless the user leaves the site or refreshes the index.jsp page. But thisi isn't happening. When I go to the index.jsp page right after I submit inforamtion, the old value of the variable is still appearing. How can I fix this? I tried MANY things. I tried using sessions to store information, but this was still giving me the same problem. I also tried doing a session.invaldiate() but again, this doesn't fix the problem. Does anyone know where I'm going wrong?
Thanks,
nafina

Show us the code. Remember to use [code] ..[/code] tags.
Or quick things to try: are you sure the browser gets a new page and doesn't display from the browser's cache? Ctrl+reload or shift+reload forces reload in some browsers. Are you sure the variable gets updated -- log the value just after updating it and just before sending it back to the browser. Theoretically, a web server can unload and reload servlets; it may be safer to put statics elsewhere (utility classes). (Though I'm not sure if a sufficiently obnoxious servlet container could unload those as well. The real place to put static data is a database, but that may be overkill.)

Is static variable serialized ???

hi
I have a static integer memeber of a serializable class. When I serialize and then deserialize this object into another object I am getting the lastest value of this variable. It looks like the variable is being serialized.
but i have read that static variables are not serialized.
can anyone clarify why i m getting the latest (updated) value??

This is not a good test. Once a class is loaded it remains loaded and all its static fields remain set with any values assign to them.
Try this instead:import java.io.*;
public class Ser implements Serializable {
    static int var = 9;
    void set() {
        var = 100;
public class DumpSer {
    public static void main(String[] args) throws Exception {
        Ser kk = new Ser();
        kk.set();
        File outFile = new File("out.dmp");
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(outFile));
        out.writeObject(kk);
        out.close();
public class LoadSer {
    public static void main(String[] args) throws Exception {
        File inFile = new File("out.dmp");
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(inFile));
        Ser jj = (Ser)in.readObject();
        in.close();
        System.out.println("Val -> "+jj.var);
}After compilation, first execute:
> java DumpSer
Then execute:
> java LoadSer
What do you see?

Static variables in CLR stored procedures

Is there really no way to use static variables shared by several CLS stored procedures in the same DLL, except by making them read only?
Or can you add new server variables and read/write those from CLR stored procedures without having to open a connection and run a query each time you need a value?
In my SP's, I would like to know the path where the database's .mdf file is stored on disk (not to access that file, but to store other files in a location that's always the same relative to the database).
I thought I had found the solution last week, after some digging through sites like stackoverflow: make it a static read-only variable, and initialize it through a function call when the module is loaded. The CLR will "forget" that it is
read only at that time.
For some reason this has worked perfectly for a week, but today it suddenly started failing -- without any code change or even a recompile, it started after a simple reboot of the test machine.
The code (just the relevant lines, in VB syntax):
Private Shared ReadOnly Datapath As String = InitDataPath()
Private Shared Function InitDataPath() As String
Try
Using cn As New SqlConnection("context connection=true"),
cmd As New SqlCommand("SELECT TOP 1 [physical_name] FROM sys.database_files WHERE type=0", cn)
cn.Open()
The "cn.open" line throws "Data access is not allowed in this context."
It did not yet do that yesterday, and the day before, and all the way back to January 6th, when I wrote that piece of code. The DLL hadn't even been recompiled since then, I was working on the application that uses the database and the stored procedures.

I think I found it, at least it works again -- I just hope it's for more than a week now.
Declare assembly as unsafe when installing it in SQL server (it was already 'EXTERNAL_ACCESS' for file I/O, but non-read-only static variables require UNSAFE).
I initialize the static variables to 'Nothing' (NULL for C# users), and instead of finding the path when the module is loaded, I added a line 'if xxx is nothing then init()' at the start of each procedure / function. Init() is a a simple initialization
routine that initializes the static variables upon first access.
added SystemDataAccess:=DataAccessKind.Read to the declaration of UDF's (not possible and not necessary for procedures, apparently, but if what caused the assembly to load was a function, it would still fail).

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.

How can I write an instance of a class in a static variable

Hi !
I have an instance of a class
Devisen dev = new Devisen();
In an other class I have a static method and I need there the content of some variables from dev.
public static void abc()
{ String text=dev.textfield.getText()
I get the errormessage, that the I cannot use the Not-static variable dev in a static variable.
I understand that I cannot reference to the class Devisen because Devisen is not static I so I had to reference to an instance. But an instance is the same as a class with static methodes. (I think so)
Is there a possibility, if I am in a static method, to call the content of a JTextField of an instance of a class ?
Thank you Wolfgang

Hallo, here is more code for my problem:
class Login {
   Devisen dev=new Devisen();
class Devisen {
   JTextField field2;
   if (!Check.check_field2()) return; // if value not okay than return
class Check {
   public static void check_field2()
     HOW TO GET THE CONTENT OF field2 HERE ?
One solution ist to give the instance to the static function, with the keyword "this"
if (!Check.check_field2(this)) return;and get the instance
public static void check_field2(Devisen dev)BUT is that a problem for memory to give every method an instance of the class ? I have 50 fields to control and I dont want do give every check_method an instance of Devisen, if this is a problem for performance.
Or do I only give the place where the existing instance is.
Hmm...?
Thank you Wolfgang

Loading the final static variables at run time.. Please help

Hello, fellow developers & Gurus,
Please help me figure out the best way to do this:
I need to load all my constants at run time. These are the public static final instance variables. The variables values are in the DataBase. How do I go about loading them.

Your original question was diffeent, but your further posts show what you really want to do:
1) all constants in 1 class
2) available readonly for other classes
3) updatable during runtime by changing in the database
Did I understand you right?
Then smiths' approach solves point 2):
Instead, make the variables available through a method
call - that way you avoid the whole final variable
versus read-only attributes problem.
//GLOBAL VARIABLES EXPOSED AS PUBLIC PROPERTIES
public final class GlobalProperties
public static int getTableSize();
public static int getRowSize();
Each "constant" should be a private static variable, and these methods simply return their values.
The variables are initialized in a static initializer by accessing the db. Ok.
You habe a table with one row containing as columns all the constants.
A method readConstants() does a "select constant1, constant2, ... from const_table" and sets all the variables.
The static initializer calls this method.
Right?
Ok, then you simply call readConstants() everytime you want to synchronize with the actual content of const_table.
Was it this?

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

Static variables after destroyApp()

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