Please try below code.
You also have to format your simpleDateFormat object and pass utilDate object inside it to create formatted date as specified by you.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateTest {
     public static void main(String[] args) throws ParseException{
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            String  strdate = "2013-09-18";
            Date utilDate = sdf.parse(strdate);
            String date=sdf.format(utilDate );
            System.out.println(date);
 }
}
We can also implement through Java8 like below:
import java.text.ParseException;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
public class DateTest {
     public static void main(String[] args) throws ParseException{
         String  strdate = "2013-09-18";
            DateTimeFormatter formatter=DateTimeFormatter.ofPattern("yyyy-MM-dd");
            LocalDate date = LocalDate.parse(strdate, formatter);
            System.out.println(date.format(formatter));
}
}
or you can also use only LocalDate to change in java util like below.
import java.time.LocalDate;
public class TestCircle {
    public static void main(String args[]){
        String  strdate = "2013-09-18";
        LocalDate date = LocalDate.parse(strdate);
        System.out.println(date);
    }
}