Java DateFormatter

DateVerifier.java

import java.text.DateFormat;
import java.text.ParseException;
import java.util.Date;
import javax.swing.InputVerifier;
import javax.swing.JComponent;
import javax.swing.JFormattedTextField;
import javax.swing.JOptionPane;


public class DatumVerifier extends InputVerifier {
   
    @Override
    public boolean verify(JComponent input) {
        
        String eing = ((JFormattedTextField)input).getText();
        
        DateFormat df1 = DateFormat.getDateInstance(DateFormat.MEDIUM);
        Date d1 = null;
        df1.setLenient(false);
        try {
                d1 = df1.parse(eing);
            } catch (ParseException e) {
                return false;
            }
        return (true);
    }
    
    @Override
    public boolean shouldYieldFocus(JComponent input) {
        if (verify(input)) {
            return true;
        } else {
            JOptionPane.showMessageDialog(null, "Kein korrektes Datumformat", "Falsches Datum", JOptionPane.WARNING_MESSAGE);
            return (false);
        }
    }
    
  
}

MainProject.java

public MainProject() {
    initComponents();
    ...
    ...
    date = new DateVerifier();
    MaskFormatter mform = null;
        
        try {
            mform = new MaskFormatter("##.##.####");
            mform.setPlaceholderCharacter('x');
            DefaultFormatterFactory dff = new DefaultFormatterFactory(mform);
            jFTF_Geburtsdatum.setFormatterFactory(dff);
            jFTF_Eintrittsdatum.setFormatterFactory(dff);
            
        } catch (ParseException e) {
            System.out.println("Falsches Format");
        }
        
        jFTF_Geburtsdatum.setInputVerifier(date);
        
        
 private boolean checkBirthday() {
        String eingabe = jFTF_Geburtsdatum.getText();

        Calendar cal = Calendar.getInstance();
        Calendar cal2 = Calendar.getInstance();
        SimpleDateFormat df = new SimpleDateFormat("dd.MM.yyyy");
        df.setLenient(false);
        int alter = 0;

        try {
            Date birth = df.parse(eingabe);
            cal.setTime(birth);
            int year = cal.get(Calendar.YEAR);
            int year2 = cal2.get(Calendar.YEAR);
            alter = year2 - year;
            System.out.print(alter);
            

        } catch (ParseException ex) {
            Logger.getLogger(DatumVerifier.class.getName()).log(Level.SEVERE, null, ex);
        }
        
        if (alter < 16) {
             JOptionPane.showMessageDialog(null, "Sie müssen 16 Jahre alt sein", "Zu jung.", JOptionPane.WARNING_MESSAGE);
            return (false);
        } else {
            return (true);
        }
        
    }
}