leetcode-Reverse Vowels of a String

Write a function that takes a string as input and reverse only the vowels of a string.

Example 1:
Given s = "hello", return "holle".

Example 2:
Given s = "leetcode", return "leotcede".

代码解析：

public class Solution {
      public static String reverseVowels(String s) {
      //  if(s == null) return null;
        int len = s.length();
        char tmp;
        //构造数组操作
        char[] arr = s.toCharArray();
        for(int i =0 ,j=len-1 ; i<j ;i++,j--){
            char chi = arr[i];
            if(!isVowels(chi)){
              j++;
              continue;
            }
            char chj = arr[j];
            if(!isVowels(chj)){
                i--;
                continue;
            }
            if(isVowels(chi)&&isVowels(chj)){    
           //因为string是不可变的~~~！！！！所以不能赋值
                tmp = arr[i];
                arr[i] = arr[j];
                arr[j]= tmp;
                //s.charAt(i)  = chj;
                //上述形式为什么老是编译不过？？？
                //因为String一旦定义好，就不可改变！！！！因此将String -> Arrays!!!
            }
        }
        //char -> string ,使用 String.valueOf(), arrays.toString()返回的不是原样式的String
       return String.valueOf(arr);
    }
    public static boolean isVowels(char ch){
        if(ch=='A'||ch=='E'||ch=='I'||ch=='O'||ch=='U'||ch=='a'||ch=='e'||ch=='i'||ch=='o'||ch=='u') return true;
        return false;
    }
    
}

总结：Array -> String三种方式：

1、String.valueOf(arr);   //直接传入

2、new String(arr); //直接传入

3、sb = new StringBuilder();

        sb.append(arr[i]); //依次传入

String -> array:   str.toCharArray(); 字符数组

char -> int      :   i = char-'0';

int -> char      :   char = i+'0';