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我的代码在编译并运行时输出文件的第一行，然后它说明了所有这些：

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(Unknown Source)
at Popcorn1.main(Popcorn1.java:59)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)

和代码：

import java.io.*;
import java.util.Scanner;
public class Popcorn1 {

public static void main(String args[]) throws FileNotFoundException {
    printHeader();
    File file;

    do {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter the the file name");
        String filename = in.next();

        file = new File(filename);
    } while (!file.exists());

    FileReader inputFile = new FileReader(file);
    Scanner inFile = new Scanner(inputFile);

    System.out.println("        PopCorn Co-op");
    System.out.println("                                      Production in Hundreds");
    System.out.println("                                      of Pint Jars Per Acre");
    System.out.println("                                  1   2   3   4   5   6");
    System.out.println("Farm Name                      ---|---|---|---|---|---|");
    System.out.println();

    // Printing out title and table header for reader to easily read data
    String errorMSG = " ";
    while (inFile.hasNextLine()) {
        String inputLine = inFile.nextLine();
        //System.out.print(inputLine);
        int position;
        String name;
        int jars;
        double acres;
        position = inputLine.indexOf(',');//Get the Location of the comma to use as a delimiter

        name = inputLine.substring(0, position); //Everything to the left of the comma is the farm name
        System.out.printf("%-31s", name);

        inputLine = inputLine.substring(position + 2, inputLine.length());           //rest of the string 
        Scanner line = new Scanner(inputLine);
        {
            //acres = 0;

            jars = 0;
            acres = 0;
            if (line.hasNextDouble()) {
                acres = line.nextDouble();
            } else {
                errorMSG += "There is missing data";
            }
            // jars = 0;
            if (line.hasNextInt()) {

                jars = line.nextInt();
            } else {
                errorMSG += "There is missing data";
            }
        }

        int starsConversion = (int) (jars / acres / 25);

        for (int i = 1; i < starsConversion; i++) {
            if (i == 20) {
                System.out.print("#");
            } else {
                System.out.print("*");
            }
        }
        if (starsConversion < 20) {
            for (int i = 1; i < (21 - starsConversion); i++) {
                System.out.print(" ");
            }
            System.out.print("|");
            {
                System.out.println(); //go to the next line
            }
        }

        System.out.println(errorMSG);
    }
}
}
4

1 回答 1

3

很难确定没有文件会发生什么，但看起来像

position = inputLine.indexOf(',');

正在返回 -1 （它在文件中找不到“，”），从而给你一个无效的索引。

计算后尝试打印出位置，以确保它是有效的。

System.out.println("Position: " + position);
System.out.println("Length: " + inputLine.length());
System.out.println("Trimmed: " + inputLine.trim().length());

如果长度为 0，或者只是空格，则其中不会有逗号。

这可以通过在阅读 nextLine 后添加以下内容来解决：

if(inputLine.trim().length() == 0) 
    continue
if(inputLine.indexOf(",") == -1) 
    System.out.println("There is no comma on this line: " + inputLine);
于 2013-10-12T01:40:05.960 回答