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Thread: non static varible from static context error

  1. #1
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    Default non static varible from static context error

    in this class i have a constructor and a main() function for testing the constructor
    theres a couple things stopping me from testing it in the command prompt tho
    the post data is a string with an ampersand in it and when i try to pass it to the main function in the command prompt it thinks that the ampersand means something, i dont know how to "escape" it
    also, i would like to know how to pass a value from the constructor to main() so i can print string test, i tried putting it outside both meathods into the class but it gave me non static context error
    //takes am address, and post data, and returns the html as a string
    import java.net.*;
    import java.io.*;
    import java.lang.*;
    public class UrlToString
    {
    	public String test = "";
    	public static void main (String[] args) throws Exception
    	{
    		//enter url and post data in cmd prompt to test
    		new UrlToString  (test,args[0],args[1]);
    		System.out.println(test);
    	}
    	//paramaters of returned string, address to get it from, and post data in th for of variable1=value1&variable2=value2...
    	UrlToString (String returnString, String inAddr, String rawData) throws Exception
    	{
    		returnString = "";
    		//connection variables
    		String agent = "Mozilla/4.0";
    		String type = "application/x-www-form-urlencoded";
    		HttpURLConnection connection = null;
    		String encodedData = URLEncoder.encode( rawData, "UTF-8");
    		//connect
    		try 
    		{
    			URL searchUrl = new URL(inAddr);
    			connection = (HttpURLConnection)searchUrl.openConnection();
    			connection.setDoOutput(true);
    			connection.setRequestMethod("POST");
    			connection.setRequestProperty( "User-Agent", agent );
    			connection.setRequestProperty( "Content-Type", type );
    			connection.setRequestProperty( "Content-Length", Integer.toString(encodedData.length()) );
    			OutputStream os = connection.getOutputStream();
    			os.write( encodedData.getBytes() );
    			os.flush();
    			os.close();
    			//check if theres an http error
    			int rc = connection.getResponseCode();
    			if(rc==200)
    			{
    				//no http response code error
    				//read the result from the server
     
    				InputStreamReader in = new InputStreamReader(connection.getInputStream());
    				BufferedReader br = new BufferedReader(in);
    				String strLine;
    				//Read File Line By Line
    				while ((strLine = br.readLine()) != null)
    				{
    					returnString = returnString.concat(strLine);
    					System.out.println(strLine);
    				}
    				return;
    			}
    			else
    			{
    				System.out.println("http response code error: "+rc+"\n");
    				return;
    			}
     
    		}
    		catch( IOException e )
    		{
    			System.out.println("search URL connect failed: " + e.getMessage());
    			e.printStackTrace();
    		}
    	}
    }


  2. #2
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    Default Re: non static varible from static context error

    It means that you're calling a non-static variable in a static method.

    For starters, try making the variable test be static.
    Last edited by javapenguin; June 4th, 2012 at 03:00 PM.

  3. #3
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    Default Re: non static varible from static context error

    A non-static variable only exists as part of an instance of a class. When you create a class object, all its non-static variables are created with it. Each class object has its own version of each non-static variable.
    A static variable is shared by all instances of a class. There is only one version of that variable.

    Why is test a class variable instead of a local variable in the main() method?
    Last edited by Norm; June 4th, 2012 at 03:15 PM.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: non static varible from static context error

    Quote Originally Posted by Norm View Post
    A non-static variable only exists as part of an instance of a class. When you create a class object, all its non-static variables are created with it. Each class object has its own version of each non-static variable.
    A static variable is shared by all instances of a class. There is only one version of that variable.

    Why is test a class variable instead of a local variable in the main() method?
    It would also work in the main method too.

    It would be better there, but I was assuming that the OP had a reason for not having the variable in the main method.

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    Default Re: non static varible from static context error

    Quote Originally Posted by Norm View Post
    A non-static variable only exists as part of an instance of a class. When you create a class object, all its non-static variables are created with it. Each class object has its own version of each non-static variable.
    A static variable is shared by all instances of a class. There is only one version of that variable.

    Why is test a class variable instead of a local variable in the main() method?
    because if i put it in main() it would pass to the constructor as local value not reference and would not change, i want test to be changed by the constructor and then go back to main after the constructor call, and then print it

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    Default Re: non static varible from static context error

    If you want the main() method to be able to reference a class variable, you need to save a reference to the created instance of the class and use that to access its variables. The posted code does NOT save a reference to the instance when it uses new to create the instance. Save the reference in a variable and use that variable to access the test variable.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: non static varible from static context error

    omfg ur right holy fuck im dumb
    ok but still, its confusing, how i get rid of this error?
    if i make the variable static i cant change it

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    Default Re: non static varible from static context error

    how i get rid of this error?
    See post #6
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    Default Re: non static varible from static context error

    wait nm i got it im dumb i nedded to pass it an empty strin, chich sems kind of wierd
    Last edited by chopficaro; June 5th, 2012 at 03:36 PM.

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    Default Re: non static varible from static context error

    Please post the full text of the error message.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: non static varible from static context error

    i got it
    sorry for the dumb questions lol i just have been doing alot of procedurally oriented programming lately not much object oreinted
    i still dont know how to pass an ampersand as part of a string to a class in the command line tho, i need to escape it or something

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    Default Re: non static varible from static context error

    Sorry, I don't know much about how you are trying to make the OS do something.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: non static varible from static context error

    That ampersand thing, I'm not sure exactly what you mean, but you don't mean a reference do you? That's C++, not Java. C is procedure oriented. C++ is object oriented.

    However, perhaps C also has pass by reference params, and I think it does actually. I know it allows you to pass pointers. (I know it does for C-Strings.)

    Java isn't that great for messing with the operating system at the lower levels. C++ would be better, as it has C and allows procedure oriented as well as OO.

    If you're talking about C++ passing &, then I don't think it would be any different, at least param wise, as passing a regular param.
    Last edited by javapenguin; June 5th, 2012 at 07:12 PM.

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