從位於私有方法中的變量讀取

Question

我有一個小問題我試圖打印位於私有方法中的幾個變量的內容。但我只是不斷找到'不能找到符號'

下面是我試圖從（包括println）讀取數據的代碼，我也是java的新手。

private void createBooking() 
{ 
    String title; 
    String firstName; 
    String lastName; 
    String bookingNo; 
    String roomType; 

    System.out.print("Enter title: "); 
    title = keyboard.next(); 
    System.out.print("Enter first name: "); 
    firstName = keyboard.next(); 
    System.out.print("Enter last name: "); 
    lastName = keyboard.next(); 
    System.out.print("Enter booking number: "); 
    bookingNo = keyboard.next(); 
    System.out.print("Enter room type: "); 
    roomType = keyboard.next(); 


    aBooking = new Booking (title, firstName, lastName, bookingNo, roomType); 

} 

public void printCustomerName() 
{ 
    System.out.println (createBooking.title); 
} 

Answer 1

你可能想要把這些變量作爲member variables，然後乾脆不使用. - 運算符訪問它。

class BookingClass { 

    // You also seem to need the following: 
    Booking aBooking; 

    String title; 
    String firstName; 
    String lastName; 
    String bookingNo; 
    String roomType; 

    private void createBooking() { 

     System.out.print("Enter title: "); 
     title = keyboard.next(); 
     System.out.print("Enter first name: "); 
     firstName = keyboard.next(); 
     System.out.print("Enter last name: "); 
     lastName = keyboard.next(); 
     System.out.print("Enter booking number: "); 
     bookingNo = keyboard.next(); 
     System.out.print("Enter room type: "); 
     roomType = keyboard.next(); 

     aBooking = new Booking(title, firstName, lastName, bookingNo, roomType); 
    } 

    public void printCustomerName() { 
     System.out.println(title); 
     // ...should perhaps be 
     // System.out.println(firstName + " " + lastName); 
    } 
} 

既然你做然而創建Booking例如，您可能想擺脫title，firstName，lastName，bookingNo和roomType，並把它們在Booking類代替。然後通過aBooking.getTitle()等訪問它們......

Answer 2

您不能訪問方法的變量，也不能使用方法作爲使用點運算符的類實例。

createBooking.something是非法的，你可以使用方法：createBooking（）

Answer 3

我完全不明白你想要做什麼。但我想你想要這樣的事情：

public String printCustomerName() { 
    // This creates the booking object (aBooking) 
    createBooking(); 

    // You can access the firstname lastname like that (I assume that you have a getter method implemented..) 
    return aBooking.getFirstName() + " " + aBooking.getLastName(); 
} 

但是，createBooking（）你應該移動到另一個地方。也許到構造有稱之爲..

Answer 4

當你做aBooking = new Booking(...)你創建與所有這些屬性的新Booking對象，並將其在aBooking現場存儲（我猜這是一個領域，因爲它沒有任何地方申報）。這意味着您有一個aBooking字段，其中包含所有這些屬性（假設Booking構造函數保存參數）。因此，要訪問這些字段，請通過aBooking字段。大概是這樣的：

System.out.println(aBooking.getTitle()); 

，或者，如果你不使用吸氣劑（你應該！）：

System.out.println(aBooking.title); 

聲明的變量的createBooking方法停止「現有」內，一旦你離開方法。他們無法以任何方式訪問（幾乎）。

Answer 5

你可能要考慮從'void'改變createBooking()方法的返回類型'Booking'，然後最後一行將成爲：

 
private Booking createBooking() 
{ 
    ... 
    ... 

    return new Booking(title, firstName, lastName, bookingNo, roomType)`` 
} 

之後，你printCustomerName()可能看起來是這樣的：

 
public void printCustomerName() 
{ 
    Booking booking = createBooking(); 
    System.out.println (booking.title); // if title is visible, which it probably shouldn't be 
    //or 
    System.out.println (booking.getTitle()); // if such a method exists... 
}