好的，所以，我是一个相对较新的程序员，我在这项任务中遇到了很大的困难。该任务是创建一个2类java代码，它将读入一个文件，一个专门的书，并将分析它来计算平均句子长度和平均字长。正确的输出应该如下所示：
> java WordMapDriver
enter name of a file
Analyzed text: /Users/moll/CS121/AliceInWonderland.txt
words of length 1: 7.257%
words of length 2: 14.921%
words of length 3: 24.073%
words of length 4: 20.847%
words of length 5: 12.769%
words of length 6: 7.374%
words of length 7: 6.082%
words of length 8: 3.012%
words of length 9: 1.812%
words of length 10: 0.820%
words of length 11: 0.501%
words of length 12: 0.236%
words of length 13: 0.134%
words of length 14: 0.083%
words of length 15 or larger: 0.001%
average sentence length: 16.917
我一直在研究这段代码但是当我运行它时，我收到了很多愤怒的红色错误消息。以下是一长串投诉：
java.lang.StringIndexOutOfBoundsException: String index out of range: 239
at java.lang.String.charAt(Unknown Source)
at WordMap.processLine(WordMap.java:26)
at Echo.readLines(Echo.java:16)
at WordMapDriver.main(WordMapDriver.java:10)
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)
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.dynamicjava.symbol.JavaClass$JavaMethod.evaluate(JavaClass.java:362)
at edu.rice.cs.dynamicjava.interpreter.ExpressionEvaluator.handleMethodCall(ExpressionEvaluator.java:92)
at edu.rice.cs.dynamicjava.interpreter.ExpressionEvaluator.visit(ExpressionEvaluator.java:84)
at koala.dynamicjava.tree.StaticMethodCall.acceptVisitor(StaticMethodCall.java:121)
at edu.rice.cs.dynamicjava.interpreter.ExpressionEvaluator.value(ExpressionEvaluator.java:38)
at edu.rice.cs.dynamicjava.interpreter.ExpressionEvaluator.value(ExpressionEvaluator.java:37)
at edu.rice.cs.dynamicjava.interpreter.StatementEvaluator.visit(StatementEvaluator.java:106)
at edu.rice.cs.dynamicjava.interpreter.StatementEvaluator.visit(StatementEvaluator.java:29)
at koala.dynamicjava.tree.ExpressionStatement.acceptVisitor(ExpressionStatement.java:101)
at edu.rice.cs.dynamicjava.interpreter.StatementEvaluator.evaluateSequence(StatementEvaluator.java:66)
at edu.rice.cs.dynamicjava.interpreter.Interpreter.evaluate(Interpreter.java:77)
at edu.rice.cs.dynamicjava.interpreter.Interpreter.interpret(Interpreter.java:47)
at edu.rice.cs.drjava.model.repl.newjvm.InterpreterJVM.interpret(InterpreterJVM.java:246)
at edu.rice.cs.drjava.model.repl.newjvm.InterpreterJVM.interpret(InterpreterJVM.java:220)
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 sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
这是我的代码。我非常感谢能得到的任何帮助：
1 import java.util.Scanner;
2 import java.io.*;
3
4 public class Echo{
5 String fileName; // external file name
6 Scanner scan; // Scanner object for reading from external file
7
8 public Echo(String f) throws IOException
9 {
10 fileName = f;
11 scan = new Scanner(new FileReader(fileName));
12}
13
14 public void readLines(){ // reads lines, hands each to processLine
15 while(scan.hasNext()){
16 processLine(scan.nextLine());
17 }
18 scan.close();
19 }
20
21 public void processLine(String line){ // does the real processing work
22 System.out.println(line);
23}
24}
___________________
1 import java.util.*;
2 import java.io.*;
3 public class WordMap extends Echo {
4 String fileName; //external text file name
5 Scanner scan; //scanner object to read external text
6 int sentencecount = 0;
7 int wordcount = 0;
8 int charcount = 0;
9 //creates an array that will be used to count average word length
10 double[] wlength = new double[15];
11 int fifteenless = 0;
12 int fifteenplus = 0;
13 public WordMap(String f) throws IOException
14 {
15 super(f);}
16
17 public void processLine(String line)
18 //creates a string array of every word
19 {String [] words = line.split("\\s+");
20 for(int a = 0; a < words.length; a++){
21 words[a] = words[a].replaceAll("[\\w]","");}
22
23 //counts words
24 wordcount = words.length;
25
26 //counts sentences by searching for sentence enders
27 for(int c = 0; c < line.length(); c++){
28 char ca = line.charAt(c);
29 if((line.charAt(ca) == '.')|| (line.charAt(ca) =='!') || (line.charAt(ca) =='?'));
30 sentencecount++ ;}
31
32 //if wordlength matches, adds one to wlength at d and to words less than 15 chars
33 for(int d = 1; d < 15; d++){
34 for(int g = 0; g < words.length; g++){
35 String temp = words[g];
36 if(d == temp.length()){
37 wlength[d]++;
38 fifteenless++;}}}}
39
40 public void calculatePercentages(){
41 {//calculate percentages with words of 15 or more characters
42 fifteenplus = wordcount - fifteenless;
43 fifteenplus = fifteenplus / wordcount;
44 fifteenplus = fifteenplus*100;}
45
46 //calculate percentages for words with 1-14 characters
47 for(int h = 1; h<15; h++){
48 wlength[h] /= wordcount;
49 wlength[h]*=100;}
50 }
51 public void reportLength(){
52 //prints out average sentence length
53 double length = wordcount / sentencecount;
54 System.out.printf("average sentence length: "+ "%5.3f",length);}
55
56 public void getWordLength(){
57 //prints out word of length percentages with a loop for 1-14 and a final one for 15+
58 for(int i = 1; i <15; i++){
59 System.out.printf("words of length " + i + ": %5.3f%%\n",wlength[i]);}
60 System.out.printf("words of 15 or more characters length: " + "%5.3f%%\n",fifteenplus);
61 }}
_______
1 import java.util.*;
2 public class WordMapDriver {
3 public static void main(String[] args) {
4 try{
5 String fileName;
6 Scanner textfile = new Scanner(System.in);
7 System.out.println("enter name of file");
8 fileName = textfile.nextLine(); //scans in file
9 WordMap k = new WordMap(fileName);//creates wordmap object
10 k.readLines(); //processes
11 k.calculatePercentages();
12 k.getWordLength(); //reports all wordlength percentages
13 k.reportLength(); //prints out average sentence length
14 }
15 catch(Exception e) //catches the ioexception
16 {e.printStackTrace();
17 }}}
*编辑：我添加了行号。此外，这可能是愚蠢的，但我不知道什么是SSCCE ** EDIT2：好的，所以我遵循了建议，现在打印出来之后是更生气的红色消息：
words of length 1: 50620.000%
words of length 2: 15690.000%
words of length 3: 2020.000%
words of length 4: 300.000%
words of length 5: 620.000%
words of length 6: 70.000%
words of length 7: 20.000%
words of length 8: 10.000%
words of length 9: 0.000%
words of length 10: 10.000%
words of length 11: 10.000%
words of length 12: 10.000%
words of length 13: 10.000%
words of length 14: 0.000%
words of 15 or more characters length: java.util.IllegalFormatConversionException: f != java.lang.Integer
答案 0 :(得分：2)
看看这一节：
for(int c = 0; c < line.length(); c++){
char ca = line.charAt(c);
if((line.charAt(ca) == '.')|| (line.charAt(ca) =='!') || (line.charAt(ca) =='?'));
sentencecount++ ;}
这里有两个问题：
变量“ca”是索引c处的字符。但是你将“ca”传递给line.charAt ... Java正在“帮助”将char转换为int，并尝试返回该索引处的字符。这不是你想要的，这就是你得到StringIndexOutOfBoundsException的原因。
您可能只想在表达式为true时增加sentenceCount，对吧？这不是代码所说的。这个“if”语句没有正文（因为与“if”语句在同一行上的分号）。一个好的做法，特别是初学者，是总是使用花括号来包围if块的主体，即使它们只是一行。
对于IllegalFormatConversionException，它告诉你％5.3f不是整数的有效转换模式（“f”表示浮点数和双精度数）。 fifteenplus被声明为int;是正确的类型？如果是这样，你可以像这样打印：
System.out.println("words of 15 or more characters length: " + fifteenplus);
如果你的意思是像所有其他线一样的百分比，那么你应该将它声明为浮点数或双数（通常你应该优先选择双浮点数，因为双精度提供更高的精度，性能差异通常是微不足道的）。
最后一点：所有百分比都以.000％结束并不奇怪吗？在Java中，将int除以int总是会得到一个int。如果需要浮点结果，则必须将其中一个参数转换为float或double，如下所示：
int a = 1;
int b = 2;
double result = (double) a / b;
尝试使用和不使用强制转换来加倍以查看差异。