How do I make the initialized variable in the if statement accessible outside of it?

I am trying to make a birthday verification program that checks if a person is underage or not, but I am having a hard time trying to get the values of the variables accessible to the Period.between().getYears() function.

 private void txt_customerbdayKeyReleased(java.awt.event.KeyEvent evt) {                                             
    int month, day, year;
    
    
    for(int x = 1; x<=txt_customerbday.getText().length(); x++){
        if(txt_customerbday.getText().length() == 3){
            month = Integer.parseInt(txt_customerbday.getText().substring(0,2));
            System.out.print(month);
        }
        
        if(txt_customerbday.getText().length() == 6){
            day = Integer.parseInt(txt_customerbday.getText().substring(3,5));
            System.out.print(day);
        }
        
        if(txt_customerbday.getText().length() == 10){
            year = Integer.parseInt(txt_customerbday.getText().substring(6,10));
            System.out.print(year);
        }
        
        if(valBD(txt_customerbday.getText()) && txt_customerbday.getText().length() == 10){
            lbl_bdaycheck.setForeground(Color.green);
            lbl_bdaycheck.setText("Good Format");
        }else{
            lbl_bdaycheck.setForeground(Color.red);
            lbl_bdaycheck.setText("Bad Format");
        }
        
        LocalDate today = LocalDate.now();
        LocalDate birthdate = LocalDate.of(year, month, day);
        Period.between(birthdate, today).getYears();
    }

is there a way for me to get those values?