java - 在 java 中从 String 中读取元音的数量

Question

那里。我需要一些帮助。我正在努力让用户输入文本，反转文本，然后读取文本中元音的数量并告诉他们反转文本中有多少元音。

public static void main(String[] args)
{
 System.out.println ("Please type in whatever you want ");
 Scanner type_input = new Scanner (System.in);
 Scanner type_input = new Scanner (System.in);
 StringBuilder type_output = new StringBuilder();
 type_output.append(type_hold);
 type_output=type_output.reverse();
 System.out.println("Is this what you types in? " + type_output);   

 for(int vowel_num = 0; vowel_num< type_hold.length(); vowel_num++)
    {
        if((type_hold.charAt(vowel_num) =='a')||(type_hold.charAt(vowel_num) =='e')||
            (type_hold.charAt(vowel_num) =='o')||(type_hold.charAt(vowel_num) =='i')||
            (type_hold.charAt(vowel_num) =='u')){    

        System.out.println("There are " + vowel_num + " vowels in " + type_hold);
    }

但是当我输入并运行它时，我得到以下信息。我不确定我在哪里搞砸了。

run:
Please type in whatever you want 
hello
Is this what you types in? olleh
There are 1 vowels in hello
There are 4 vowels in hello

编辑:我想通了。感谢大家的帮助!

Answer 1

1. 什么是type_hold？没看到你实例化了，你在用。
2. 什么 vowel_num？您正在遍历字符串的索引？还是你数过的元音数量？

计算字符串中的元音字母应该怎么做:

假设 index 是我们当前正在扫描的字符串的索引，vowel_count 是您遇到的元音的计数。

int vowel_count = 0;
for(int index = 0; index < type_hold.length(); index++) {
    if((type_hold.charAt(index) =='a') || 
       (type_hold.charAt(index) =='e') || 
       (type_hold.charAt(index) =='o') || 
       (type_hold.charAt(index) =='i') || 
       (type_hold.charAt(index) =='u')){

         // character at vowel_index is a vowel.
         // you have encountered 1 more vowel! 
         System.out.println("Character at " + index + " is a vowel.");
         vowel_count ++;
     }
}

System.out.println("There are " + vowel_count + " vowels in " + type_hold);