Accessing JTextField in a different class and adding it to a String

Question

I'm making a program with Java and I have the problem that I want to write a file in one class. In another class I want to overwrite this file, if the name of the file already exsists. However the first class uses a JTextField in which you can enter a number. That number is than added to the filename. That works perfect, but in the second class it won't. I used an association, but it gave me a nullpointer exception. Can someone help?

    public void actionPerformed(ActionEvent e) {
        //make file
        String fileName = "Week " + tf1.getText();
        File planning = new File(fileName + ".txt");

        // save file
        if (e.getSource() == b2) {
// file does't exists yet and all field are filled out
            if (!planning.exists() && allesGevuld()) {
                FileWriter fw;
                try {
                    fw = new FileWriter(planning, false);
                    BufferedWriter bw = new BufferedWriter(fw);
                    bw.write(toString());
                    bw.close();
                    fw.close();
                    JOptionPane.showMessageDialog(null,
                            "De weekplanning is opgeslagen!", "Succes",
                            JOptionPane.PLAIN_MESSAGE);
                    dispose();

                } catch (IOException e1) {
                    System.out.println("Exception ");
                }
                // no everything is filled in
            } else if (!allesGevuld()) {
                JOptionPane.showMessageDialog(null,
                        "Niet alle velden zijn ingevuld!", "Mislukt",
                        JOptionPane.PLAIN_MESSAGE);
            }
            // to overwriting frame
            else if (planning.exists() && allesGevuld()) {
                OverschrijvenFrame ov = new OverschrijvenFrame(planningFrame);
                ov.setVisible(true);

            }
        }
    }

Second class:

if (e.getSource() == overschrijf) {
            // overschrijven van file
            String fileName = "Week"+ ;//this is where the number should be overwritten
            File planning = new File(fileName + ".txt");

            // delete the file which will be overwritten
            planning.delete();

            // new file
            File nieuw = new File(fileName + ".txt");

            FileWriter fw;
            try {
                fw = new FileWriter(nieuw);
                BufferedWriter bw = new BufferedWriter(fw);
                bw.write(planningFrame.toString());
                bw.close();
                fw.close();
                dispose();

            } catch (IOException e1) {
                System.out.println("Exception ");
            }
        }
    }

Answer 1

What your problem?

If you cannot call tf1.getText() from second class because tf1 is private in first class -> make it public or add public static variable to hold the file name that can refer from second class.

Answer 2

Use Java IO

http://docs.oracle.com/javase/7/docs/api/java/io/File.html#exists%28%29

import java.io.*;
//...
new File("pathToFile").exists()

OR use Java NIO

http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html

import java.nio.file.*;
//...
Files.exists(Paths.get("pathToFile"))