java - Implement clearing prefilled fields/ check if answer is correct -

i want change followingmethod thelastname field not pre filled , checks in private boolean isinputvalid if entered value equal thelastname field. @ moment field pre filled , checks if field empty or not. how should code looks 2 changes?

package ch.makery.address.view;  import javafx.fxml.fxml; import javafx.scene.control.textfield; import javafx.stage.stage;  import org.controlsfx.dialog.dialogs;  import ch.makery.address.model.person;   /**  * dialog train word.  *   *   */ public class englishtraindialogcontroller {      @fxml     private textfield firstnamefield;     @fxml     private textfield lastnamefield;     @fxml        private stage dialogstage;     private person person;     private boolean okclicked = false;      /**      * initializes controller class. method automatically called      * after fxml file has been loaded.      */     @fxml     private void initialize() {     }      /**      * sets stage of dialog.      *       * @param dialogstage      */     public void setdialogstage(stage dialogstage) {         this.dialogstage = dialogstage;     }      /**      * sets person edited in dialog.      *       * @param person      */     public void setperson(person person) {         this.person = person;          firstnamefield.settext(person.getfirstname());         lastnamefield.settext(person.getsecondenglish());      }      /**      * returns true if user clicked ok, false otherwise.      *       * @return      */     public boolean isokclicked() {         return okclicked;     }      /**      * called when user clicks check , go back.      */     @fxml     private void handleok() {         if (isinputvalid()) {             person.setfirstname(firstnamefield.gettext());             person.setlastname(lastnamefield.gettext());               okclicked = true;             dialogstage.close();         }     }      /**      * called when user clicks cancel.      */     @fxml     private void handlecancel() {         dialogstage.close();     }      /**      * validates user input in text fields.      *       * @return true if input valid      */     private boolean isinputvalid() {         string errormessage = "";          if (firstnamefield.gettext() == null || firstnamefield.gettext().length() == 0) {             errormessage += "no valid german word!\n";          }         if (lastnamefield.gettext() == null || lastnamefield.gettext().length() == 0) {             errormessage += "no valid english word!\n";          }           if (errormessage.length() == 0) {             return true;         } else {             // show error message.             dialogs.create()                 .title("wrong spelling")                 .masthead("please correct!")                 .message(errormessage)                 .showerror();             return false;         }     } }