为什么在这段代码中使用布尔变量？

Question

我是 java 的新手，我们班上有一个我没有的作业 很明白。

程序应将输入的单词翻译成 Pig Latin。所以每个以元音开头的单词应该显示为“word + lay”，每个以辅音开头的单词应该显示为“word_without_the_consonant_at_the_beginning + consonant + ay”。

我的问题是我不明白为什么需要这样做 被包括在内。有人可以向我解释吗？特别是因为我已经 在代码的开头输入这些变量。

        firstVowelFound = false;
        firstIndex = 0;       

在这种情况下，为什么我需要 firstVowelFound？为什么我必须包括它 在这里：

      while ((firstIndex < scannedWords.length()) && !firstVowelFound)

这是代码，老师更正了。粗体字是那些 我不明白。希望你能帮助我。谢谢！！

import java.util.Scanner;


public class PigLatin2
{

  public static void main(String[] args)
  {
    Scanner keyboard = new Scanner(System.in);
    Scanner wordScanner;

    String
      wordInput = "",
      scannedWords = "",
      pigLatinWord = "";

    int
      firstIndex = 0;

    char
      firstLetter;

    boolean
      firstVowelFound = false;

    while (keyboard.hasNextLine()) //as long as there is input, read input.
    {
      wordInput = keyboard.nextLine().toLowerCase();
      wordScanner = new Scanner(wordInput);

      while (wordScanner.hasNext()) //read input to find out the words
      {
        scannedWords = wordScanner.next();

        **firstVowelFound = false;
        firstIndex = 0;    


        //for the following part, the program looks for the first Index of 
        //each word. If the letters of switch are included, boolean is 
        //true.

        while ((firstIndex < scannedWords.length()) && !firstVowelFound)**
        {
          firstLetter = scannedWords.charAt(firstIndex);

          switch (firstLetter)
          {
            case 'a':
            case 'e':
            case 'i':
            case 'o':
            case 'u':
              **firstVowelFound = true;**
              break;

            default: 
              // no vowel occurred in the word, so look for more words.
              firstIndex++;
          }
         }
        /*the following parts create pigLatin Words. When index is 0, all 
          words starting with a vowel will be word + lay, any other word 
          will display word with the first letter + ay displayed at the end 
          of the word */ 

        if (firstIndex == 0)
        {
          pigLatinWord = scannedWords + "lay";
        }
        else
        {
          pigLatinWord = scannedWords.substring(1) + 
          scannedWords.substring(0,1) + "ay";
        }
      }
      System.out.println("Pig Latin for your entered word is " + 
      pigLatinWord + 
      " ");
    }

  }
}

Answer 1

firstVowelFound 用于确保当找到第一个元音时 while 循环中断。实际上没有它，循环将是无限的。

可能代码中令人困惑的地方是switch 中的break。它不会使程序退出 while 循环，而只是在 switch 之外。