Java: "this"关键字的问题

Question

这个问题已经有答案了:

Non-static variable cannot be referenced from a static context (15 个回答)

已关闭 10 年前。

我正在尝试使用类 Library{} 和 Book{} 创建一个 Java 包“mylib”。

以下是类库{}的代码:

/*
 Create collection of books
 List books and status
 User input:
   'B' - Borrow a book
   'R' - Reserve a book
   'I' - Return a book
   'X' - Exit program
*/

package mylib;

public class Library {

    public static void main(String[] args) {
        Book[] MyBooks = new Book[3];
        Book x;

        MyBooks[0] = new Book("The Lover's Dictionary", "Levithan, D.", 211);
        MyBooks[1] = new Book("White Tiger", "Adiga, A.", 304);
        MyBooks[2] = new Book("Thirteen R3asons Why", "Asher, J.", 336);

        for (int i = 0; i < MyBooks.length; i++) {
            x = MyBooks[i];
            System.out.println((i + 1) + " " + x.sTitle);
        }
    }
}

以下是 Book{} 类的代码:

package mylib;

class Book {
    // Declare fields
    byte iStatus;
    int iPages;
    String sTitle, sAuthor;
    String sBorrowedBy, sReservedBy;
    String sDueDate, sReturnDate;

    public static final byte BORROWED = 0, AVAILABLE = 1, RESERVED = 2;

    // Constructor
    public Book(String Title, String Author, int Pages) {
        this.sTitle = Title;
        this.sAuthor = Author;
        this.iPages = Pages;
        this.iStatus = this.AVAILABLE;
    }

    // Borrow method
    static void borrowBook(String Borrower, String Due) {
        if (this.iStatus == this.AVAILABLE) {
            this.sBorrowedBy = Borrower;
            this.sDueDate = Due;
            this.iStatus = this.BORROWED;
        } else if (this.iStatus == this.RESERVED
                && this.sReservedBy == Borrower) {
            this.sBorrowedBy = Borrower;
            this.sDueDate = Due;
            this.sReservedBy = "";
            this.iStatus = this.BORROWED;
        }
    }

    /*
     * static int reserveBook(String Borrower) {
     * 
     * }
     * 
     * static void returnBook(String Return) {
     * 
     * }
     */
}

上面的部分代码是教授给出的。我注释掉了空方法并测试了程序只是为了看看它是否可以编译。

我的 this 关键字有 14 个错误。有什么帮助吗？

Answer 1

在这个方法中

static void borrowBook(String Borrower, String Due) {

您不能在静态上下文中使用this

据我所知，没有必要将该方法设为静态。

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