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Reading from a .txt file to an ArrayList

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Join Date: Feb 2009

Posts: 25

Reputation: BrianK123 is an unknown quantity at this point

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BrianK123

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Reading from a .txt file to an ArrayList

Feb 15th, 2009

What I am trying to do is read from a file to an ArrayList and then display it using a JOptionPane. The only problem is the code i am having trouble with is in an ActionListener and I believe somehow I have created an infinite while loop because when I click the button the ActionListener is attached to, noting happens.
The .txt file I am trying to read from:

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Java Syntax (Toggle Plain Text)

Mary Anne
A
Joe Wright
B
Andrew Heath
A

and the troublesome code segment:

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public class ViewClassesListener implements ActionListener
    {           
        public void actionPerformed (ActionEvent event)
        {
            //entering the class and grade information into arrays
            try
            {
                FileInputStream APStream=new FileInputStream("CompSciAP.txt");
                DataInputStream APDIS = new DataInputStream(APStream);
                BufferedReader APBR=new BufferedReader(new InputStreamReader(APDIS));
 
                String temp="";
 
                while ((temp=APBR.readLine()) != null)
                {
                    //infinite loop?
                    CompSciAP.add(temp);
                }
                APStream.close();
            }
            catch (Exception e)
            {
                System.err.println("Error: " + e.getMessage());
            }
 
            //displaying the information
            stop=CompSciAP.size();
            index=0;
            while (index<=stop)
            {
                //or is this the infinite loop?
                APLabel.setText(APLabel.getText()+CompSciAP.get(index)+"\n");
                index++;
            }
            CompSciAPPane.showMessageDialog(All, APLabel, "Computer Science AP", JOptionPane.PLAIN_MESSAGE);
        }
    }
public class ViewClassesListener implements ActionListener
    {           
        public void actionPerformed (ActionEvent event)
        {
            //entering the class and grade information into arrays
            try
            {
                FileInputStream APStream=new FileInputStream("CompSciAP.txt");
                DataInputStream APDIS = new DataInputStream(APStream);
                BufferedReader APBR=new BufferedReader(new InputStreamReader(APDIS));
                
                String temp="";
                
                while ((temp=APBR.readLine()) != null)
                {
                    //infinite loop?
                    CompSciAP.add(temp);
                }
                APStream.close();
            }
            catch (Exception e)
            {
                System.err.println("Error: " + e.getMessage());
            }
            
            //displaying the information
            stop=CompSciAP.size();
            index=0;
            while (index<=stop)
            {
                //or is this the infinite loop?
                APLabel.setText(APLabel.getText()+CompSciAP.get(index)+"\n");
                index++;
            }
            CompSciAPPane.showMessageDialog(All, APLabel, "Computer Science AP", JOptionPane.PLAIN_MESSAGE);
        }
    }

Please help me!

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Join Date: Feb 2009

Posts: 25

Reputation: BrianK123 is an unknown quantity at this point

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BrianK123

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Re: Reading from a .txt file to an ArrayList

Feb 15th, 2009

I think I solved it. I changed the

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stop=CompSciAP.size();
            index=0;
            while (index<=stop)
stop=CompSciAP.size();
            index=0;
            while (index<=stop)

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 Java Syntax (Toggle Plain Text) 
stop=CompSciAP.size();
            index=0;
            while (index<stop)
stop=CompSciAP.size();
            index=0;
            while (index<stop)

That should be it. I spent hours trying to solve the problem and all it was was a little = sign!

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Join Date: Mar 2007

Posts: 686

Reputation: sillyboy is on a distinguished road

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sillyboy

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Re: Reading from a .txt file to an ArrayList

Feb 15th, 2009

nice work, althought I wouldn't think that would cause a infinite, more likely an ArrayIndexOutOfBounds... anyway, it's solved.

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Join Date: Nov 2008

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verruckt24 verruckt24 is offline

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Re: Reading from a .txt file to an ArrayList

Feb 16th, 2009

My judgement here is that there was no infinite loop at all. When you are running a GUI based program you don't get to see any exceptions thrown by the JVM. Now, when your index counter was reaching 'size' then the JVM would have been throwing an exception which since your program being a GUI program you wouldn't have had an oppurtunity to see. This happens becuase the exception is thrown to the standard output stream which is typically the console. Since the program halted at that instruction the instruction

 Help with Code Tags 
 java Syntax (Toggle Plain Text) 
CompSciAPPane.showMessageDialog(All, APLabel, "Computer Science AP", JOptionPane.PLAIN_MESSAGE);
CompSciAPPane.showMessageDialog(All, APLabel, "Computer Science AP", JOptionPane.PLAIN_MESSAGE);

never got executed and hence you never got to see the JOption Pane which led you to believe that since there was no output, there must have been an infinite loop somewhere.