on-the-square-peg-problem-main/square-peg-applet/src/MeinFileFilter.java
import javax.swing.filechooser.*;
import java.io.File;

public class MeinFileFilter extends FileFilter {

    String[] extensions;
    String description;

    public MeinFileFilter(String ext) {
        this(new String[] { ext }, null);
    }

    public MeinFileFilter(String[] exts, String descr) {
        // Clone and lowercase the extensions
        extensions = new String[exts.length];
        for (int i = exts.length - 1; i >= 0; i--) {
            extensions[i] = exts[i].toLowerCase();
        }
        // Make sure we have a valid (if simplistic) description
        description = (descr == null ? exts[0] + " files" : descr);
    }

    public boolean accept(File f) {
        // We always allow directories, regardless of their extension
        if (f.isDirectory()) {
            return true;
        }

        // Ok, it's a regular file, so check the extension
        String name = f.getName().toLowerCase();
        for (int i = extensions.length - 1; i >= 0; i--) {
            if (name.endsWith(extensions[i])) {
                return true;
            }
        }
        return false;
    }

    public String getDescription() {
        return description;
    }
}