java 字符串倒叙

public static void operStr(String str){

char[] a = new char[str.length()];
a = str.toCharArray();

              //方法一

// char[] b = new char[a.length];

// for (int i = a.length-1; i >= 0 ; i--) {

// b[a.length-1-i] = a[i]; 
// }

            //方法二

char temp = 0;
for (int i = 0; i < a.length/2; i++) {
temp = a[i];
a[i] = a[a.length-1-i];
a[a.length-1-i] = temp;
}
String s = new String(a);
System.out.println(s);
}