格式化：String 无法转换为 String[]

Question

Using the data array, create instances of books and store them in a one-dimensional array of Book, called bookArray. Using the quantity array, walk through the book array and calculate the total charge per book sold. Print in a dialog box the book title, the book isbn, and the total charge for each book. Then, print the grand total of all books sold.

到目前为止我已经这样做了，但是我在 JOptionPane 和格式方面遇到了问题。

错误

$ javac BookTest.java
BookTest.java:41: error: incompatible types: String cannot be converted to String[][]
        dataArray +=String.format(" %s, %s ", b.getTitle(), b.getIsbn());
                                 ^
1 error

代码：

import javax.swing.JOptionPane;

public class BookTest { 
   public static void main(String args[]) {
      String dataArray  [][]=
         {{ "Fiction", "Abraham Lincoln Vampire Hunter", "Grahame-Smith", "Wiley", "NY", "978-0446563079", "13.99", "222"},
          {"Fiction", "Frankenstein", "Shelley", "Prescott", "GA", "978-0486282114", "7.99", "321"},
          {"NonFiction", "Life of Kennedy", "Jones", "Pearson", "MT", "758-29304566", "12.90", "biography"},
          {"Fiction", "Dracula", "Stoker", "Addison", "CA", "978-0486411095","5.99", "145"},
          {"Fiction", "Curse of the Wolfman", "Hageman", "Wesley", "MA", "B00381AKHG", "10.59", "876"},
          {"NonFiction", "How to Pass Java", "Willis", "Wiley"," NY", "444-395869790", "1.99", "technology"},
          {"Fiction", "The Mummy", "Rice", "Addision", "CA", "978-0345369949", "7.99", "954"},
          {"NonFiction", "History of Texas", "Smith", "Prescott", "CA", "123-683947687", "9.75", "history"}
         };

      Book bookArray[] = new Book [8];

      for (int i = 0; i < bookArray.length; i++) {
         if (dataArray[i][0].equals("Fiction")) {
            Publisher p = new Publisher(dataArray[i][3], dataArray[i][4]);
            bookArray[i] = new Fiction(dataArray[i][1], dataArray[i][2], dataArray[i][5],
               p, Double.parseDouble(dataArray[i][6]), dataArray[i][7]);
         } else {
            Publisher p = new Publisher(dataArray[i][3], dataArray[i][4]);
            bookArray[i] = new NonFiction(dataArray[i][1], dataArray[i][2], dataArray[i][5],
               p, Double.parseDouble(dataArray[i][6]), dataArray[i][7]);
         }
      }

      for (Book b:bookArray) {
        dataArray +=String.format(" %s, %s ", b.getTitle(), b.getIsbn());
        JOptionPane.showMessageDialog(null, dataArray);     
      }
   }        
}

Answer 1

String.format returns a String 根据文档。您正在尝试将 String 连接到二维数组。

dataArray +=String.format(" %s, %s ", b.getTitle(), b.getIsbn());

在上面的行中，您可能想从二维数组中访问一个位置，例如 dataArray[0][0]，然后进行连接。类似于：

dataArray[0][0] +=String.format(" %s, %s ", b.getTitle(), b.getIsbn());

Answer 2

不要用你的dataArray在消息框中输出东西。 使用一个 String 变量.

for (Book b : bookArray) {
    String bookOutput = String.format(" %s, %s ", b.getTitle(), b.getIsbn());
    JOptionPane.showMessageDialog(null, bookOutput);
}

更好，在你的 Book class 中添加一个 toString() 那 returns String.format(" %s, %s ", getTitle(), getIsbn()) 然后像 this:

这样循环

for (Book b : bookArray) {
    JOptionPane.showMessageDialog(null, b.toString());
}

但是，如果你想输出每本书的价格然后是总价，你的循环看起来更像this：

double totalPrice = 0.0;
for (int i = 0; i < bookArray.length; i++) { //can't use foreach because of use of parallel arrays bookArray & quantityArray
    Book b = bookArray[i];
    double price = b.getPrice() * quantityArray[i];
    totalPrice += price;
    String bookStr = String.format(" %s, %s %s", b.getTitle(), b.getIsbn(), 
        DecimalFormat.getCurrencyInstance().format(price));
    JOptionPane.showMessageDialog(null, bookStr);
}
String totalStr = String.format("Total Charge: %s", 
    DecimalFormat.getCurrencyInstance().format(totalPrice)));
JOptionPane.showMessageDialog(null, totalStr);

格式化：String 无法转换为 String[]

Formatting: String cannot be converted to String[]

java

arrays

formatting

joptionpane