Question

The following method only writes out the latest item I have added, it does not append to previous entries. What am I doing wrong?

public void addNew() {
    try {
        PrintWriter pw = new PrintWriter(new File("persons.txt"));
        int id = Integer.parseInt(jTextField.getText());
        String name = jTextField1.getText();
        String surname = jTextField2.getText();
        Person p = new Person(id,name,surname);
        pw.append(p.toString());
        pw.append("sdf");
        pw.close();
    } catch (FileNotFoundException e) {...}
}

Answer 1

The fact that PrintWriter‘s method is called append() doesn’t mean that it changes mode of the file being opened.

You need to open file in append mode as well:

PrintWriter pw = new PrintWriter(new FileOutputStream(
    new File("persons.txt"), 
    true /* append = true */)); 

Also note that file will be written in system default encoding. It’s not always desired and may cause interoperability problems, you may want to specify file encoding explicitly.