印刷方法

Question

我试图打印一个方法的内容(购买(字符串isbn，双价，int副本)，但没有运气。在编写以下代码时，

import java.util.Scanner; 
import java.io.*; 

public class Store { 
    public static void main(String[] args) throws Exception {
    Book[] books = readInventory();

        for (Book book : books) {
            System.out.printf("ISBN: %s, Price: %f, Copies: %d%n", book.getISBN(), book.getPrice(), book.getCopies()); 
        }
    String isbn;
    double price;
    int copies;
    purchase(isbn, price, copies);

    }

    public static Book[] readInventory() throws Exception {
        Book[] books = new Book[10];
        java.io.File file = new java.io.File("../instr/prog4.dat");
        Scanner fin = new Scanner(file);
        String isbn;
        double price;
        int copies;
        int i = 0;

        while (fin.hasNext()) {
            isbn = fin.next();
                if (fin.hasNextDouble()); {
                    price = fin.nextDouble();
                }
                if (fin.hasNextInt()); {
                    copies = fin.nextInt();
                }
             Book book = new Book(isbn, price, copies);
             books[i] = book;
             i++;
        }
        fin.close();
        return books;
 }

    public static Book[] purchase(String isbn, double price, int copies, Book[] books) {
        int itemsSold = 0;
        double totalMade = 0;
        Scanner input = new Scanner(System.in);
        int desiredCopies = 0;

        System.out.println("Please enter the ISBN number of the book you would like to purchase: ");
            String desiredIsbn = input.next();
            for(int index = 0; index < books.length; index++) {
                if(!books[index].getISBN().equals(desiredIsbn))
                    System.out.println("We do not have that book in our inventory.");
                if(books[index].getISBN().equals(desiredIsbn) && copies == 0)
                    System.out.println("That book is currently out of stock.");
                if(books[index].getISBN().equals(desiredIsbn) && copies > 0) {
                    System.out.println("How many copies of this book would you like to purchase?"); 
                        desiredCopies = input.nextInt(); }
                        if(desiredCopies > copies)
                            System.out.println("We only have " + copies + "in stock. Please select another quantity: ");
                            desiredCopies = input.nextInt();
                        // copies = copies - desiredCopies
                        double total = price * desiredCopies;
                    System.out.println("Thank you for your purchase, your order total is: $" + total);
                    itemsSold += desiredCopies;
                    totalMade += total;
                    // update array
                    System.out.print(books[index]);
                    System.out.println("We sold " + itemsSold + " today.");
                    System.out.println("We made $" + totalMade + "today.");
            }   
        return books;
        }

    public void displayInfo(Book[] books) {
        for(int x=0; x<books.length; x++) {
             System.out.println("ISBN: " + books[x].getISBN() + "\n Price: " +
                books[x].getPrice() + "\n Copies: " + books[x].getCopies());
        System.out.print(books[x]);
        }
    }
}

class Book {
 private String isbn;
 private double price;
 private int copies;

 public Book() {
 }

 public Book(String isbnNum, double priceOfBook, int copiesInStock) {
  isbn = isbnNum;
  price = priceOfBook; 
  copies = copiesInStock;
 }

 public String getISBN() {
  return isbn;
 }

 public double getPrice() {
  return price;
 }

 public int getCopies() {
  return copies;
 }

 public void setISBN(String isbn) {
  this.isbn = isbn;
 }

 public void setPrice(double price) {
  this.price = price;
 }

 public void setCopies(int copies) {
  this.copies = copies;
 }

   @Override
    public String toString() {
        return String.format("ISBN: %s, Price: %f, Copies: %d%n",
            this.getISBN(), this.getPrice(), this.getCopies());
    }

}

我得到编译器错误

Store.java:21: purchase(java.lang.String,double,int,Book[]) in Store cannot be applied to (java.lang.String,double,int)
        purchase(isbn, price, copies);
        ^
1 error

如果我评论一下：

String isbn;
double price;
int copies;
purchase(isbn, price, copies);

main()方法的一部分，程序打印数组，但没有其他任何内容。我需要程序打印的购买方法，包括更新的数组(我仍然不知道如何这样做，任何帮助，对此将不胜感激)。

关于我怎样才能让这件事奏效，有什么建议吗？如果可以的话，我想尽可能接近我编写的代码，过去几天我一直在做这个工作，但是大约一个半小时后就要到期了，所以我已经没有时间了。提前谢谢。

Answer 1

您的purchase方法使用与您调用的签名不同的签名。

purchase需要String, double, int, Book[]作为参数，但是您正在尝试用String, double, int调用它。尝试添加一个图书阵列。

最重要的是，纵观purchase，看起来大多数参数甚至都没有被使用。您应该考虑使用这些参数或删除它们。

PS:您可能需要考虑使用像Eclipse、Netbeans或IntelliJ这样的IDE来帮助捕获这些常见的错误:)

Answer 2

编译器错误是因为您传递了三个参数，而该方法需要四个参数。以下代码将编译：

purchase(isbn, price, copies, books);

但是，您的代码在其他方面看上去是错误的，因为您没有为isbn、price或copies分配任何值。Book类已经包含这些值，因此只需要向打印方法提供一个Book对象数组。

例如，将购买方法更改为：

public static Book[] purchase(Book[] books) {
  int itemsSold = 0;
  double totalMade = 0;
  Scanner input = new Scanner(System.in);
  int desiredCopies = 0;

  System.out
      .println("Please enter the ISBN number of the book you would like to purchase: ");
  String desiredIsbn = input.next();
  for (int index = 0; index < books.length; index++) {
    if (!books[index].getISBN().equals(desiredIsbn))
      System.out.println("We do not have that book in our inventory.");
    if (books[index].getISBN().equals(desiredIsbn) && books[index].getCopies() == 0)
      System.out.println("That book is currently out of stock.");
    if (books[index].getISBN().equals(desiredIsbn) && books[index].getCopies() > 0) {
      System.out
          .println("How many copies of this book would you like to purchase?");
      desiredCopies = input.nextInt();
    }
    if (desiredCopies > books[index].getCopies())
      System.out.println("We only have " + books[index].getCopies()
          + "in stock. Please select another quantity: ");
    desiredCopies = input.nextInt();
    // copies = copies - desiredCopies
    double total = books[index].getPrice() * desiredCopies;
    System.out.println("Thank you for your purchase, your order total is: $"
        + total);
    itemsSold += desiredCopies;
    totalMade += total;
    // update array
    System.out.print(books[index]);
    System.out.println("We sold " + itemsSold + " today.");
    System.out.println("We made $" + totalMade + "today.");
  }
  return books;
}

其他一些注意事项：

• 尝试一个for-每一个循环，例如for (Book book : books) {
• 考虑使用货币类型而不是double。
• 不要在需要变量之前声明变量。

Answer 3

您在purchase()方法中传递了错误的参数数。你已经宣布了

public Book[] purchase(String isbn, double price, int copies, Book[] books)//taking four arguments

即有四个参数，但调用它时只传递三个参数，即

purchase(isbn, price, copies);//but you are calling it by passing only three parameters reason for the error