Finding Class in a static context

Is there any way through reflection of getting the Class I am in during a static method?
Or is this impossible??
e.g.
class foo{
    void nonStatic(){
        Class c = this.getClass(); // OK
    static void isStatic(){
        Class c = // ?????? no this pointer
}Any ideas?
Thanks,
Nick

public class MyClass
public static specialMethod()
Class c = MyClass.class;

Similar Messages

Does class/static context make an object?

Howdy all!
I know that for every class there exists a 'static context' in which all static members of a class operate - methods, variables or classes.
I also know that there is a method getClass() which retrieves a Class object.
My question is: does this mean that Java considers the class or static context of a class to be an object in its own right?
Having static members of a class implies that you have a static state - and an obvious choice is to have an object to store that state.
Is this correct? Is there something I have missed?
Rob

Hi,
Being no expert, I would say that you are on the right track. Each class loaded by a java.lang.ClassLoader is represented in Java by an object of class java.lang.Class.
The static memebers of a class are local to this instance of the class. This can be easily verified by loading the same class two times (can be done, for example, by writing your own ClassLoader). Then when you set a static member in an object of the first class, you will not see the change in objects instantiated from the later class, although it is of the same type.

Question about static context when using classes

hey there.
i'm pretty new to java an here's my problem:
public class kreise {
     public static void main (String[] args) {
         //creating the circles
         create a = new create(1,4,3);
         create b = new create(7,2,5);
         System.out.println(a);
         System.out.println(b);
         //diameters...unimportant right now
         getDiameter a_ = new getDiameter(a.radius);
         getDiameter b_ = new getDiameter(b.radius);
         System.out.println(a_);
         System.out.println(b_);
         //moving the circles
         double x = 2;
         double y = 9;
         double z = 3;
         a = create.move();
         System.out.println(a);
}creating a circle makes use of the class create which looks like this:
public class create {
    public double k1;
    public double k2;
    public double radius;
    public create(double x,double y,double r) {
        k1 = x;
        k2 = y;
        radius = r;
    public create move() {
        k1 = 1;
        k2 = 1;
        radius = 3;
        return new create (k1,k2,radius);
    public String toString() {
    return "Koordinaten: "+k1+" / "+k2+". Radius: "+radius;
}now that's all totally fine, but when i try to usw create.move to change the circles coordinates the compiler says that the non-static method move() can't be referenced from a static context. so far i've seen that my main() funktion MUST be static. when declaring the doubles k1, k2, and radius in create() static it works, but then of course when having created the second circle it overwrites the first one.
i pretty much have the feeling this is very much a standard beginner problem, but searching for the topic never really brought up my problem exactly. thanks in advance!

You can't access a non-static method from within a static context. So, you have to call move() from outside of the main method. main has to be static because, in short, at least one method has to be static because there haven't been any objects initialized when the program is started. There are more fundamental problems than with just the static context issue.
I'm confused by your code though. You call create.move(), but this would only be possible if move() was static, and from what I see, it's not. Now that's just one part of it. My second issue is that the logic behind the move() method is very messy. You shouldn't return a newly instantiated object, instead it should just change the fields of the current object. Also as a general rule, instance fields should be private; you have them as public, and this would be problematic because anything can access it.
Have you heard of getters and setters? That would be what I recommend.
Now, also, when you are "moving" it, you are basically creating a new circle with completely differently properties; in light of this, I've renamed it change(). Here would be my version of your code:
public class CircleTester {
    public static void main (String[] args)
         //Bad way to do it, but here's one way around it:
         new CircleTester().moveCircle();
    private void moveCircle()     //really a bad method, but for now, it'll do
        Circle a = new Circle(1,4,3);
        Circle b = new Circle(7,2,5);
        System.out.println(a);
        System.out.println(b);
        //diameters. Don't need to have a new getDiameter class
        double a_ = a.getRadius() * 2;     //Instead of doing * 2 each time, you could have a method that just returns the radius * 2
        double b_ = b.getRadius() * 2;
        System.out.println(a_);
        System.out.println(b_);
        //move the circle
        a.change(2,9,3);
        System.out.println(a);
public class Circle {
    private double k1;
    private double k2;
    private double radius;
    public Circle(double x,double y,double r)
        k1 = x;
        k2 = y;
        radius = r;
    public void change(int x, int y, int r)
        k1 = x;
        k2 = y;
        radius = r;
    public String toString()
         return "Koordinaten: "+k1+" / "+k2+". Radius: "+radius;
    public double getRadius()
         return radius;
}On another note, there is already a ellipse class: http://java.sun.com/j2se/1.5.0/docs/api/java/awt/geom/Ellipse2D.html

Painting jpeg in java application: non-static method ... static context

Hi!
I simply want to show a jpeg within a java application. Showing the jpeg in an applet is no problem (see code below). But I have difficulties to translate this code to a java application. No matter what I try to load the jpeg, I end up with the following error:
non-static method createImage() cannot be referenced from a static context
How can I surround it? Thanx in advance for your help!
Working applet
import java.applet.*;
import java.awt.*;
public class shJpAp extends javax.swing.JApplet {
Image pic;
/** Creates a new instance of shJpAp */
public shJpAp() {
public void init() {
pic=getImage(getCodeBase(), "lemmer.jpg");
prepareImage(pic,this);
public void paint (Graphics g) {
g.drawImage(pic,0,0,this);
Application
import java.awt.*;
public class shJp extends javax.swing.JFrame {
Image pic;
/** Creates new form shJp */
public shJp() {
initComponents();
//pic = java.awt.Toolkit.getImage("lemmer.jpg");
---> pic = java.awt.Toolkit.createImage("lemmer.jpg");
---> prepareImage(pic, this);
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
private void initComponents() {
addWindowListener(new java.awt.event.WindowAdapter() {
public void windowClosing(java.awt.event.WindowEvent evt) {
exitForm(evt);
pack();
/** Exit the Application */
private void exitForm(java.awt.event.WindowEvent evt) {
System.exit(0);
* @param args the command line arguments
public static void main(String args[]) {
new shJp().show();
// Variables declaration - do not modify
// End of variables declaration
public void paint( Graphics g) {
g.drawImage(pic, 0,0,this);
}

Hi,
just want to add a solution I found in some textbook (see code below). I hate finding every possible question in the internet, but seldom fitting answers.....
But again, one little thing pushed me close to my first heart attack: The code below works well when executed by foot (...java showPic...). In the NetBeans 3.6 the frame refuses to show the pic!
I am looking for an appropiate forum - but if anyone of you can help, it would be very nice ;-)
import java.awt.*;
import java.awt.event.*;
public class showPic extends Frame {
Image pic;
public showPic() {
addWindowListener( new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
pic = getToolkit().getImage("lemmer.jpg");
setSize(200,100);
setVisible(true);
public void paint(Graphics g) {
if (pic != null) {
g.drawImage(pic,60,20,this);
public static void main( String[] args ) {
new showPic();
}

Accessing static context from instances...

Hello,
I'm confused with something. Accessing static elemnts or static methods from an instance is allowed. I think it shouldn't be allowed. Because static context is class-wide so objects shouldn't be able to access them.
Am I wrong..?

I find it confusing.. If something is class-wide then
it should only be accessed by the class, not the
instance of the class...That depends on the nature or purpose of the information. Static information or methods are a useful way of sharing information between instances of the same class, while still having that information protected from other classes. Other examples are constants which are used within each instance. Why should each instance have a separate copy of exactly the same constant?
You could even argue that any method which does not need any instance information should be declared static, but it is not always necessary to make that distinction.
Eclipse (mine at least :) ) gives a warning when you access a static
method/variable 'through' an instance, telling you that you should access >the method/variable in a static way.This warning usually occurs if you call a static method in a non static way. For example, if you declare a class called MyClass with a static method myMethod() and you have an instance assigned to variable anInstance, you should call the method using MyClass.myMethod() instead of anInstance.myMethod().
Graeme

Non-static variable being used in static context

I am currently attempting to write a basic user login system using basic applets. I have two JTextFields named "userText" and "passText".
What i am attempting to do is use the ".getText()" method to get the text out of the JTextField and verifying the string against a string already in a file using the bufferedReader, etc.
However when i try to compare the string in the file with the one in the text field using the following code:
if ((line.compareTo(username)) == 0)
i get the following error...
"non-static variable being used in a static context"
Any ideas?

The static method doesn't know about instances of the class instead you pass the instance to the method:
static public void myMethod(MyClass instance, String var) {
if(instance.line.compareTo(var))
And then the call would be:
MyClass.myMethod(anInstance, userName);

Cannot find class javax.swing.JOptionPane

Hello,
I imported the class
import javax.swing.JOptionPane;and written as a first line of my code in the form of a .java file.
but error occurs as : cannot find the class javax.swing.JOptionPane. What should I do.
Thank you.

Are you doing something likeimport javax.swing.JOptionPane;
class Test {
    public static void main(String args[]) {
        JOptionPane.showMessageDialog(null, "Testing",
                "Testing", JOptionPane.INFORMATION_MESSAGE);
}Mark

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.

Non-static variable from a static context

This is the error i get . If i understand the error correctly it says im using a static variable when i shouldnt be? Or is it the other way round? below the error is the actual code....
The error...
Googler.java:27: non-static variable this cannot be referenced from a static context
          submitButton.addActionListener(new ButtonHandler());The code...
          JButton submitButton = new JButton("Submit Query");
          submitButton.addActionListener(new ButtonHandler());

thanks for the response.
I have already tried what you said but I tried it again anyway and i get the same error more less...
Googler.java:28: non-static variable this cannot be referenced from a static context
          ButtonHandler buttonHandler = new ButtonHandler();here is part of my code
public class Googler
static JTextField input1, input2;
     public static void main(String[] args)
          JFrame myFrame = new JFrame("Googler v1.0");
          Container c = myFrame.getContentPane();
          JLabel lab1 = new JLabel("Enter Google Query:");
          JLabel lab2 = new JLabel("Enter Unique API Key:");
          input1 = new JTextField(15);
          input2 = new JTextField(15);
          JRadioButton radSearch = new JRadioButton("Search Query");
          JRadioButton radCached = new JRadioButton("Cached Query");
          JButton submitButton = new JButton("Submit Query");
          ButtonHandler buttonHandler = new ButtonHandler();
          submitButton.addActionListener(buttonHandler);
          ButtonGroup group = new ButtonGroup();
          group.add(radSearch);
          group.add(radCached);Ive tried declaring buttonHandler as a static variable and this dosn't work either. I've never had this problem before it must be something silly im missing...?
Thanks
Lee

Non-static variable from static context?

Hi,
I've created a program using swing components
and I've set up a addActionListener to a button,
button.addActionListener(this);
when try and compile I get the following error:
non-static variable this cannot be referenced from a
static context
button.addActionListener(this);
I've checked site and my notes I don't seem to have
done anything different from programs that have compiled
in the past.
I'm currently doing a programming course so I'm fairly
new to Java, try not to get to advanced on me :)
Thx in advance for any help.
Chris

Well what is declared static? If I remeber right this error means that you have a static method that is trying to access data it does not have access to. Static methods cannot access data that is intance data because they do not exist in the instance (not 100% sure about this but I believe it is true, at the very least I know they do not have access to any non-static data). Post some more of your code like where you declare this (like class def) and where you set up the button.

Non static variable in static context

import java.util.Scanner;
public class project4_5 {
     int die1, die2;
     int comptotal = 0, playertotal = 0, turntotal = 0;
     int turn, comprun = 0;
     String playername;
     String action = ("R");
     Scanner scan = new Scanner(System.in);
        public static void main (String[] args)
        PairOfDice mydie = new PairOfDice();
     System.out.println("!!!!!!PIG!!!!!!");
     System.out.println();
     System.out.println("Enter your name! ");
     playername = scan.nextLine();
     while(playertotal>100 && comptotal>100){
     while(action.equalsIgnoreCase("R")){
               System.out.println(playername+" roll or pass the die (R/P) ");
               action = scan.nextLine();
               if(action.equalsIgnoreCase("P"))
                    break;
               mydie.roll();
               die1 = mydie.getFace1();
               die2 = mydie.getFace2();
               System.out.println("You rolled a "+die1+" and a "+ die2);
               if(die1==1||die2==1){
                    turntotal = 0;
                    System.out.println("You rolled a 1, you lose your points"
                    +" for this turn.");
                    break;
               else if(die1==1&&die2=1){
                    playertotal = 0;
                    System.out.println("You rolled snake eyes, all points have"
                    + " been lost.");
                    break;
               else
               turntotal= turntotal+die1+die2;
               System.out.println("Would you like to roll or pass? (R/P)");
                       if(action.equalsIgnoreCase("P")){
                            playertotal = playertotal+turntotal;
                            turntotal = 0;
               while(turntotal<=20||turns!=run){
               turn = (int) (Math.random() * 5 + 1);
               mydie.roll();
               die1 = mydie.getFace1();
               die2 = mydie.getFace2();
               System.out.println("Computer rolled a "+die1+
               " and a "+ die2);
               if(die1==1||die2==1){
                    turntotal = 0;
                    System.out.println("Computer rolled a 1 he loses hi points"
                    +" for this turn.");
                    break;
               else if(die1==1&&die2=1){
                    playertotal = 0;
                    System.out.println("Computer rolled snake eyes, his points have"
                    + " been lost.");
                    break;
               else
               turntotal= turntotal+die1+die2;
               comprun++;
               turntotal = 0;
   }here is code for a dice game i made...and when i compile it practically every variable gets an error saying non-static variable can not be referenced from a static context....anyone kno what this means or how i go about fixing it...i think it has something to do with assigning the return variable from my getFace method to die1 and die 2...idk how to fix it tho
if u need it my die class is below
public class PairOfDice
     int faceValue1, faceValue2;
     public PairOfDice()
          faceValue1 = 1;
          faceValue2 = 1;
     public void roll()
          faceValue1 = (int) (Math.random() * 6 + 1);
          faceValue2 = (int) (Math.random() * 6 + 1);
     public int getFace1 ()
          return faceValue1;
     public int getFace2 ()
          return faceValue2;


It means what it says -- that you're trying to use a non-static thing (like a method or a field) from a static thing (like your main method).
You can either make everything static (which isn't great -- it flies in the face of object-oriented programming) or instantiate an object.
If you want to do the latter, then try this: make your main method instantiate a method, and run it, like this:
public static void main(String[] argv) {
    project4_5 game = new project4_5();
    game.play();
}Then create a method called play:
public void play() {
// put everything that's currently in main() in here
}See if that fixes it for you.

Non-static variable total cannot be referenced from a static context

i am trying to write a program that uses the if-else statements and when i wrote my program i got "non-static variable total cannot be referenced from a static context" for three lines of my input.
A:\Disks.java:20: non-static variable total cannot be referenced from a static context total = (10000 * .95 + ((diskCount - 10000) * .85));
^
A:\Disks.java:22: non-static variable total cannot be referenced from a static context total = (diskCount * .95);
^
A:\Disks.java:24: non-static variable total cannot be referenced from a static context System.out.print(total);
^
Do you know what I did wrong?

I apologise in advance for the general tone of this reply.....
Ummm, let me think for a second... You referenced a non static
variable from a static context. Yup, yup. That's it !
If you can't figure this out, you really need to do a Java tutorial or
buy a text book. Basically though, total is a member of some class
and you are trying to use it from a static function. I bet you have
something like:
public class Test {
    public int total;
    // blah blah blah
    public static void main(String[] args) {
        // This won't work cos "total" is a member and we are static
        System.out.println(total);
        // This works cos now you have an instance to pull total
        // out of.
        Test t = new Total();
        System.out.println(t.total);
}

Non-static variable aceYears cannot be referenced from a static context

This is my error...
investment.java:53: non-static variable aceYears cannot be referenced from a static context
lwInvest.numberAceYears(aceYears);
^
This is my code...
public static void main (String[] args)
investment.Invest.numberAceYears(aceYears);
and more code
String termInvested = JOptionPane.showInputDialog
("Please enter the amount of years to invest your investment.");
int intTermInvested = Integer.parseInt(termInvested);
and yet more code..
public void numberAceYears (int aceYears)
for (int aY = 5 ; aY <= aceYears; aY++)
double aceInterest = aceCoBalance * aceCoRate /100;
aceCoBalance = aceCoBalance + aceInterest;
aceYears = aceYears + aY;
Suggestions?

Short version: Either make the variable in question static, or create an instance of your class and use that to access it. Either one will work, but one probably suits your design better. It's up to you to figure out which one.
For details, see the relevant section of your favorite Java book or tutorial, or poke around here:
http://www.google.com/search?q=java+non+static+variable+cannot+be+referenced+from+a+static+context

Non-static variable change cannot be referenced from a static context

My compiler says: : non-static variable change cannot be referenced from a static context
when i try to compile this. Why is it happening?
public class change{
int coin[] = {1,5,10,25,50};
int change=0;
public static void main(){
int val = Integer.parseInt(JOptionPane.showInputDialog(null, "Type the amount: ", "Change", JOptionPane.QUESTION_MESSAGE));
change = backtrack();
}

A static field or method is not associated with any instance of the class; rather it's associated with the class itself.
When you declared the field to be non-static (by not including the "static" keyword; non-static methods and fields are much more common so it's the default), that meant that the field was a property of an object. But the static main method, being static, didn't have an object associated with it. So there was no "change" property to refer to.
An alternative way to get this work, would be to make your main method instantiate an object of the class "change", and put the functionality in other instance methods.
By the way, class names are supposed to start with upper-case letters. That's the convention.

Non-static method cannot be referenced from a static context

Hey
Im not the best java programmer, im trying to teach myself, im writing a program with the code below.
iv run into a problem, i want to call the readFile method but i cant call a non static method from a static context can anyone help?
import java.io.*;
import java.util.*;
public class Trent
String processArray[][]=new String[20][2];
public static void main(String args[])
String fName;
System.out.print("Enter File Name:");
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
fName="0";
while (fName=="0"){
try {
fName = br.readLine();
System.out.println(fName);
readFile(fName);
catch (IOException ioe)
System.out.println("IO error trying to read File Name");
System.exit(1);
public void readFile(String fiName) throws IOException {
File inputFile = new File(fiName); //open file for reading
FileReader in = new FileReader(inputFile); //
BufferedReader br = new BufferedReader(
new FileReader(inputFile));
String first=br.readLine();
System.out.println(first);
StringTokenizer st = new StringTokenizer(first);
while (st.hasMoreTokens()) {
String dat1=st.nextToken();
int y=0;
for (int x=0;x<=3;){
processArray[y][x] = dat1;
System.out.println(y + x + "==" + processArray[y][x]);
x++;
}

Hi am getting the same error in my jsp page:
Hi,
my adduser.jsp page consist of form with field username,groupid like.
I am forwarding this page to insertuser.jsp. my aim is that when I submit adduser.jsp page then the field filled in form should insert into the usertable.The insertuser.jsp is like:
<% String USERID=request.getParameter("id");
String NAME=request.getParameter("name");
String GROUPID=request.getParameter("group");
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mynewdatabase","root", "root123");
PreparedStatement st;
st = con.prepareStatement("Insert into user values (1,2,4)");
st.setString(1,USERID);
st.setString(2,GROUPID);
st.setString(4,NAME);
// PreparedStatement.executeUpdate();//
}catch(Exception ex){
System.out.println("Illegal operation");
%>
But showing error at the marked lines lines as:non static method executeupdate can not be referenced from static context.
Really Speaking I am newbie in this java world.
whether you have any other solution for above issue?
waiting Your valuable suggestion.
Thanks and regards
haresh

Finding Class in a static context

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