Java实现字符串反转

public class Reverse {
public static String reverse1(String str) {
if (str == null || str.length() <= 1)
return str;
return new StringBuilder(str).reverse().toString();
}

public static String reverse2(String str) {
if (str == null || str.length() <= 1)
return str;
return reverse2(str.substring(1)) + str.charAt(0);
}

public static String reverse3(String str) {
if (str == null || str.length() <= 1)
return str;
char[] ca = new char[str.length()];
for (int i = 0; i < str.length(); i++) {
ca[i] = str.charAt(str.length() - i - 1);
}
return new String(ca);
}

public static void main(String[] args) {
String s = "hello world";

System.out.println(reverse1(s));
System.out.println(reverse2(s));
System.out.println(reverse3(s));
}
}