显示非法格式转换错误 找不到错误?图书程序

Question

我正在尝试创建一个程序，用户可以在其中输入有关书籍的信息并获得输出，但代码似乎不起作用。我收到下面的错误。我是新编程，所以不知道代码有什么问题。

Exception in thread "main" java.util.IllegalFormatConversionException: f != java.lang.String
at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:4302)
at java.util.Formatter$FormatSpecifier.printFloat(Formatter.java:2806)
at java.util.Formatter$FormatSpecifier.print(Formatter.java:2753)
at java.util.Formatter.format(Formatter.java:2520)
at java.util.Formatter.format(Formatter.java:2455)
at java.lang.String.format(String.java:2940)
at C3519369.main(C3519369.java:47)

这是下面的代码。

import java.util.Scanner;
public class books{
public static void main (String[] args) {
    final int MAX_BOOKS = 1;
    Scanner scan = new Scanner (System.in);
    String[] title = new String [MAX_BOOKS];
    String[] author = new String [MAX_BOOKS];
    double[] price = new double [MAX_BOOKS];
    String[] publisher = new String [MAX_BOOKS];
    String[] isbn = new String [MAX_BOOKS];
    for (int i = 0; i < MAX_BOOKS; i ++) {


        System.out.print("Enter the Title: ");
        title [i] = scan.nextLine ();
        System.out.print("Enter the Author:         ");
        author [i] = scan.nextLine ();
        System.out.print("Enter the Price:        ");
        price [i] = scan.nextDouble ();
        System.out.print("Enter the Publisher:        ");
        publisher [i] = scan.nextLine ();
        System.out.print("Enter the ISBN:        ");
        isbn [i] = scan.nextLine ();
        scan.nextLine();
    }
    System.out.println ();
    System.out.println (String.format(("%-20s %-10s %-10s %-10s"), "Title", "Author", "Price", "Publisher"));
    System.out.println (String.format(("%-20s %-10s %-10s %-10s"), "=====", "=====", "=====", "========="));
    final String PRETTY_PRINT = "%-20s %-10s %-10s %6.2f";
    double totalPrice = 0.0;
    for (int i =0; i < MAX_BOOKS; i ++) {
        totalPrice += price [i];
        System.out.println(String.format (PRETTY_PRINT, title [i], author [i], price [i], publisher [i], isbn [i]));
    }
    System.out.println ();
    System.out.println ("Total Price: " + String.format ("%6.2f", totalPrice));
    System.out.println ("Average Price: " + String.format ("%6.2f", totalPrice / MAX_BOOKS));
    scan.close ();
    }
}

Answer 1

这里 ：

//PRETTY_PRINT = "%-20s %-10s %-10s %6.2f";
System.out.println(String.format (PRETTY_PRINT, title [i], author [i], price [i], publisher [i], isbn [i]));

字符串格式与给定的参数不匹配：%6.2f应该用于显示float但你给它一个String（isbn是一个String[]）。

您可以像这样重现错误：

//Try to replace "yolo" with a float.
System.out.println(String.format("%6.2f", "yolo"));