Why does JFileChooser.setSelectedFile behave this way?

Question

Hello,
I'm trying to ovverride the setSelectedFile() method. However in doing so I've discovered the following:
Every user selection (single-click on a file/folder) results in two calls: one with the file null, and another with the selected file.
Why??
I could work around it, but i don't understand what sense it makes. I looked into JFileChooser code, and there doesn't seem to be an apparent 2nd call to setSelectedFile.
This is my work around code. However having to say if (f != null) { and   if (!f.getName().equals("Dir")) { doesn't sound enough data hiding for me.
class InstallDirChooser extends JFileChooser {
    @Override
    public void setSelectedFile(final File f) {
        if (f != null) {
            if (!f.getName().equals("Dir")) {
                super.setSelectedFile(new File(f, "Dir"));
            } else {
                super.setSelectedFile(f);
            System.out.println(getSelectedFile().getAbsolutePath());
public class NewClass {
    public static void main(String[] args) {
        final InstallDirChooser c = new InstallDirChooser();
        c.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
        c.setSelectedFile(new File("Dir"));
        int rVal = c.showSaveDialog(null);
        if (rVal == JFileChooser.APPROVE_OPTION) {
            final File db = c.getSelectedFile();
            db.mkdir();
}

Answer 1

I'm not sure what you're trying to do here, but at
first glance "TestK t = new TestK();" inside the for
loop seemed unusual.
If you place it before the loop it works fine.I guess what he is trying to ask is that why is that if you use the new operator in the code, you donot get the exception while if you dont use it you do get one. While in any case either you use it or not you are supposed to get a new String as per the String API.
Well thats an interesting observation and I have no explanation as to why is this happening. I do remember that thread where somebody pointed this out as a use of the String(String original) construtor. Furtehr adding on to that the API states about this constructor the following
Initializes a newly created String object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string.
so I donot get why not using it would cause the exception to be thrown. I have tested the code though and it seems to behave as pointed in the original post.
Interesting question though, food for thought.