java - 为什么返回空白？

Question

这来 self 们老师给我们的单词库，我应该返回最长的单词，其中仅包含键盘顶行的字符。目前它返回空白。请帮忙。

//What's the longest word only using the top row of the keyboard?      
   public static void Question6() {  

      String longestWordSoFar = " ";
      System.out.println("Question 6:");
      for(int i = 1; i < WordList.numWords(); i++) // check every word in wordlist
      {
          if(topRow(WordList.word(i))) { // if the length is greater than the previous word, replace it
          {  
              if(WordList.word(i).length() > longestWordSoFar.length())            
                  longestWordSoFar=WordList.word(i);
              }      
          }

      }
      System.out.println("longest word including top row: " + longestWordSoFar);
      System.out.println();
      return;
   }

public static boolean topRow(String word) {

       for(int i = 0; i < word.length(); i++) {
       //return true if the word has all of the letters in the top row of the keyboard
               if (word.charAt(i) != 'q') {
               return false;
               }
               if (word.charAt(i) != 'w') {
               return false;
               }
               if (word.charAt(i) != 'e') {
               return false;
               }
               if (word.charAt(i) != 'r') {
               return false;
               }
               if (word.charAt(i) != 't') {
               return false;
               }
               if (word.charAt(i) != 'y') {
               return false;
               }
               if (word.charAt(i) != 'u') {
               return false;
               }
               if (word.charAt(i) != 'i') {
               return false;
               }
               if (word.charAt(i) != 'o') {
               return false;
               }
               if (word.charAt(i) != 'p') {
               return false;
               }   
        }
        return true;
   }

Answer 1

改用正则表达式。如果 s 是 String 类型，则使用

s.matches("[qwertyuiop]+")

匹配键盘顶部一行上的一个或多个字母。我将不区分大小写留给您。

附:我打赌答案是“打字机”。