线程“main”中的异常 java.lang.StringIndexOutOfBoundsException：字符串索引超出范围：Pig Latin 为 -1

Question

我正在尝试制作一个程序，该程序将文本文件翻译成猪拉丁语。 当我运行它时，它说线程“main”中的异常 java.lang.StringIndexOutOfBoundsException: String index out of range: -1。 你能帮我修一下吗。 我将向您展示代码中不正确的部分。

public static void piglatenizeFile(String fileNameIn, String fileNameOut) 
   {
      Scanner infile = null;
      String g = "";
      String output = "";
      String eachLetter = "";
      int index= -1;
      String vowels = "aeiouAEIOU";
      try
      {
         infile = new Scanner(new File(fileNameIn));  
      }
      catch(IOException e)
      {
         System.out.println("oops");
         System.exit(0);   
      }
   
      PrintWriter outfile = null;
      try
      {
         outfile = new PrintWriter(new FileWriter(fileNameOut));
      }
      catch(IOException e)
      {
         System.out.println("File not created");
         System.exit(0);
      }
      while(infile.hasNext()){// while txt has next line
         String sentence = infile.nextLine();// looks at next line
         String[] word = sentence.split(" ");//splits sentence to array of words
         for(int i=0;i<word.length;i++){//goes through every word in the sentence
            g =word[i].replaceAll("[\\p{Punct}]+", "");// replaces all punctuation
            for(int t=0;t<g.length();t++){// goes through every letter in each word
               eachLetter = g.substring(t,t+1);// eachLetter= each letter in noPunct
               if(eachLetter == vowels){
                  index = t;
                  t = g.length();
               }
            }
            output = g.substring(index)+ g.substring(0,index)+"ay";//ERROR
            outfile.print(output+" ");
         }
         outfile.print("\n");
      }

      outfile.close();
      infile.close();
   }
}

Answer 1

在 java 中，当你在字符串上使用 == 时，字符串会在 stringpool( https://www.journaldev.com/797/what-is-java-string-pool ) 上使用，所以if(eachLetter == vowels){它总是假的索引将始终保持在 -1，因为 JustAnotherDeveloper 说使用 equals 并且您的 if 条件有时会为真