Java字符串反转常见的几种方式？

 1 public class StringReverse {
 2     public static void main(String[] args) {
 3         String str="hello";
 4         System.out.println(reverse(str));
 5         
 6     }
 7     public static StringBuilder reverse(String str){
 8         return new StringBuilder(str).reverse();
 9     }
10 }

 1 public class StringReverse {
 2     public static void main(String[] args) {
 3         String str="hello";
 4         System.out.println(reverse(str));
 5 
 6     }
 7     public static String reverse(String str){
 8         int len=str.length();
 9         if(len==1)
10             return str;
11         //subString(1)表示把字符串中索引1之后的字串拿出来；charAt(0)表示取字符串的第一个字符
12         return reverse(str.substring(1))+str.charAt(0);
13     }
14 }

 1 public class StringReverse {
 2     public static void main(String[] args) {
 3         String str="hello";
 4         System.out.println(reverse(str));
 5 
 6     }
 7     public static String reverse(String str){
 8         String ans="";
 9         for(int i=str.length()-1;i>=0;i--){
10             char c=str.charAt(i);
11             ans+=c;
12         }
13         return ans;
14     }
15 }

 1 public class StringReverse {
 2     public static void main(String[] args) {
 3         String str="hello";
 4         System.out.println(reverse(str));
 5 
 6     }
 7     public static String reverse(String str){
 8         char[] chars = str.toCharArray();
 9         String ans="";
10         for (int i = chars.length - 1; i >= 0; i--) {
11             ans+=chars[i];
12         }
13         return ans;
14     }
15 }