java - java クラスのメソッドで日付属性が機能しない

Question

これは、顧客クラスの属性です。

public class Customer {
private String customer_username;
private String customer_password;
private String name;
private String surname;
private Date dateOfBirth;
private String address;
private String postcode;
private String email;
(...)

これは、txt ファイルに保存するメソッドです。Date dateOfBirth のエラーがあります。機能させるために何を含めればよいかわかりません。

public void saveToFile(){
    FileWriter out = null;
    try{
        out = new FileWriter("CustomerDetails.txt", true);
        out.append("Customer Username:   ");
        out.append(customer_username);
        out.append(System.getProperty("line.separator"));
        out.append("Customer Password:   ");
        out.append(customer_password);
        out.append(System.getProperty("line.separator"));
        out.append("Name:   ");
        out.append(name);
        out.append(System.getProperty("line.separator"));
        out.append("Surname:   ");
        out.append(surname);         
        out.append(System.getProperty("line.separator"));
        **out.append("Date of Birth:   ");**
        **out.append(dateOfBirth);**
        out.append(System.getProperty("line.separator"));
        out.append("Address:   ");
        out.append(address);
        out.append(System.getProperty("line.separator"));
        out.append("Postcode:   ");
        out.append(postcode);
        out.append(System.getProperty("line.separator"));
        out.append("Email:   ");
        out.append(email);
        out.append(System.getProperty("line.separator"));
        out.append(System.getProperty("line.separator"));
        out.append("**********************************");
        out.append(System.getProperty("line.separator"));
        out.append(System.getProperty("line.separator"));
        out.close();
    }catch (IOException ioe){  
}

Answer 1

try

out.append(dateOfBirth.toString());

If you don't like the format, you can use a SimpleDateFormat to change it. (see the Documentation)

Answer 2

dateOfBirthはDateタイプのオブジェクトであり、標準のsysoで印刷することはできません。

使用日を印刷したい：dateOfBirth.toString());