MissingFormatArgumentException错误

Question

我成功编制了库存计划:

// Inventory.java part 1
// this program is to calculate the value of the inventory of the Electronics Department's cameras

import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;

public class Inventory
{
   public static void main(String[] args)
   {
       // create Scanner to obtain input from the command window
       Scanner input = new Scanner (System.in);

       String name;
       int itemNumber; // first number to multiply
       int itemStock; // second number to multiply
       double itemPrice; //
       double totalValue; // product of number1 and number2



   while(true){       // infinite loop
              // make new Camera object

      System.out.print("Enter Department name: "); //prompt
      String itemDept = input.nextLine(); // read name from user

            if(itemDept.equals("stop"))  // exit the loop
           break;


 {
 System.out.print("Enter item name: "); // prompt
 name = input.nextLine(); // read first number from user
 input.nextLine();


     }

 System.out.print("Enter the item number: "); // prompt
 itemNumber = input.nextInt(); // read first number from user
 input.nextLine();
  while( itemNumber <= -1){
 System.out.print("Enter valid number:"); // prompt
 itemNumber = input.nextInt(); // read first number from user input.nextLine();
 } /* while statement with the condition that negative numbers are entered
 user is prompted to enter a positive number */

 System.out.print("Enter number of items on hand: "); // prompt
 itemStock = input.nextInt(); // read first number from user
 input.nextLine();
  while( itemStock <= -1){
 System.out.print("Enter positive number of items on hand:"); // prompt
 itemStock = input.nextInt(); // read first number from user
 input.nextLine();
 } /* while statement with the condition that negative numbers are entered
 user is prompted to enter a positive number */

 System.out.print("Enter item Price: "); // prompt
 itemPrice = input.nextDouble(); // read second number from user
 input.nextLine();
  while( itemPrice <= -1){
 System.out.print("Enter positive number for item price:"); // prompt
 itemPrice = input.nextDouble(); // read first number from user
 input.nextLine();
 } /* while statement with the condition that negative numbers are entered
 user is prompted to enter a positive number */


 Cam camera = new Cam(name, itemNumber, itemStock, itemPrice);

 totalValue = itemStock * itemPrice; // multiply numbers

 System.out.println("Department name:" + itemDept); // display Department name
 System.out.println("Item number: " + camera.getItemNumber()); //display Item number
 System.out.println("Product name:" + camera.getName()); // display the item
 System.out.println("Quantity: " + camera.getItemStock());
 System.out.println("Price per unit" + camera.getItemPrice());
 System.out.printf("Total value is: $%.2f\n" + totalValue); // display product

       } // end while method

   } // end method main

}/* end class Inventory */

class Cam{

private String name;
private int itemNumber;
private int itemStock;
private double itemPrice;
private String deptName;

public Cam(String name, int itemNumber, int itemStock, double itemPrice) {
this.name = name;
this.itemNumber = itemNumber;
this.itemStock = itemStock;
this.itemPrice = itemPrice;
   }

   public String getName(){
      return name;
      }



   public int getItemNumber(){
   return itemNumber;

}

   public int getItemStock(){
   return itemStock;

}

   public double getItemPrice(){
    return itemPrice;

}

}

C:\ Java> java Inventory
输入部门名称:Electronics
输入项目名称:camera
输入项目编号:12345
输入项目数量:8
输入项目价格:100.50
部门名称:Electronics
项目编号:12345
产品名称:camera
数量: 8单位
价格100.5
总价值为:
$线程"main"中的异常java.util.MissingFormatArgumentException: java.io.PrintStream.format 中java.util.Formatter.format(未知来源)的
格式说明符'.2f' (来源不明) 在java.io.PrintStream.printf(来源不明) 在Inventory.main(Inventory.java:82)

我似乎遇到这种格式错误,看不出原因.

Answer 1

如果您正在使用printf,则需要将占位符指定为printf参数以及格式字符串.在您的情况下,您通过附加金额传递单个字符串,因此错误.

System.out.printf("Total value is: $%.2f\n" + totalValue)

应该被替换

System.out.printf("Total value is: $%.2f\n", totalValue)

Answer 2

这就是问题:

System.out.printf("Total value is: $%.2f\n" + totalValue);

我想你的意思是:

System.out.printf("Total value is: $%.2f\n", totalValue);

换句话说,指定替换占位符的值,而不是仅使用字符串连接将值添加到格式字符串的发送.

一般来说,当你得到一个你不理解的例外时,你应该看看它的文档.在这种情况下,文档相当清楚:

当存在没有相应参数的格式说明符或参数索引引用不存在的参数时,抛出未经检查的异常.

因此,您需要在代码中检查两件事:

• 你有没有相应参数的格式说明符吗？
• 你有一个参数索引引用一个不存在的参数吗？

您没有在格式字符串中指定任何参数索引,因此它必须是第一种情况 - 事实上它确实如此.