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

Question

I'm trying to call my createFile method from the OpenFile class in my main method, but I keep getting the error saying that I cannot call a non-static variable from a static context.

I did try calling OpenFile of = new OpenFile(); inside my main method, but that didn't work so I'm currently declaring OpenFile above my main method which works fine, however every time I try to use one of OpenFiles methods I get the same error.

I've tried prefacing a few things with static but that just causes my IDE to show an Erroneous sym type error, which I think is caused by whatever is causing the other error.

Here is createFile from OpenFile:

public class OpenFile {

    private Formatter file;

    public void createFile() throws FileNotFoundException{

        try{
            file = new Formatter("test.txt");
        } catch(Exception e) {
            System.out.println("Error creating file.");
    }
    }

and here is my main method:

OpenFile of = new OpenFile();

public static void main(String[] args) {
    // TODO code application logic here

    of.createFile();
    intro();
    createAndShowRibbon();
    createAndShowNormalUI();

}

Is it something to do with Formatter? I've never used it before.

Thanks.

http://stackoverflow.com/a/6730716/2864740 , http://stackoverflow.com/a/4308942/2864740 , http://stackoverflow.com/a/7638196/2864740 — user2864740, Nov 19 '13 at 04:22
Please search first. It has nothing to do with the `Formatter` type. — user2864740, Nov 19 '13 at 04:22
Too fundamental question, need to explore first i feel too :(. — Jayasagar, Nov 19 '13 at 05:06

score 5 · Accepted Answer · answered Nov 19 '13 at 04:20

5

OpenFile of = new OpenFile();

should be

static OpenFile of = new OpenFile();

You're accessing it from your static void main method. If this variable is not declared static, it will not be available to the method when it is statically executed.

answered Nov 19 '13 at 04:20

Jeroen Vannevel

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Seems to run! Although it runs when I add static to `OpenFile` but only when I also add `throws FileNotFoundException` to the main method, what's up with that? – JmJ Nov 19 '13 at 04:27
@JoshJahans: you are calling `of.createFile();` which throws that very same exception. Since it's being thrown there instead of caught (using `try { } catch { }`), it has to be either thrown or caught in the next method, `main` in this example. – Jeroen Vannevel Nov 19 '13 at 04:29
You can't call something that doesn't exist. Since you haven't created an object, the non-static method doesn't exist yet. A static method (by definition) always exists. – hitesh141 May 21 '15 at 12:05

score 2 · Answer 2 · answered Nov 19 '13 at 04:37

Since main method in java is most popular method among all beginners and they try to put program code there they face "non-static variable cannot be referenced from a static context" compiler error when they try to access a non static member variable inside main in Java which is static.

Please take a look at this article
Why non-static variable cannot be referenced from a static context?

In your case you have to make the OpenFile of = new OpenFile(); instantiation to be static like as shown below in order to access that in main method which is a static method.

static OpenFile of = new OpenFile();  // should be static for accessing within main method
public static void main(String[] args) {

    of.createFile();
    intro();
    createAndShowRibbon();
    createAndShowNormalUI();

}

score 1 · Answer 3 · answered Nov 19 '13 at 04:21

1

The following is non-static.

OpenFile of = new OpenFile();

But you're calling it from a main method, which is static.

Try changing to:

static OpenFile of = new OpenFile();

answered Nov 19 '13 at 04:21

Nick Grealy

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score 1 · Answer 4 · answered Nov 19 '13 at 04:49

1

in the static method u can call Class methods or variables which is static but u can't call instance variables or method in

answered Nov 19 '13 at 04:49

Antwan

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

4 Answers4