Java中如何使用栈来反转字符串？

package net.javaguides.corejava.string;
import java.util.Stack;
/**
* 
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingStack {
// Function to reverse a string in Java using a stack and character array
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// create an empty stack of characters
Stack < Character > stack = new Stack < Character > ();
// push every character of the given string into the stack
char[] ch = str.toCharArray();
for (int i = 0; i < str.length(); i++)
stack.push(ch[i]);
// start from index 0
int k = 0;
// pop characters from the stack until it is empty
while (!stack.isEmpty()) {
// assign each popped character back to the character array
ch[k++] = stack.pop();
}
// convert the character array into string and return it
return String.copyValueOf(ch);
}
public static void main(String[] args) {
String str = "javaguides";
str = reverse(str); // string is immutable
System.out.println("Reverse of the given string is : " + str);
}
}

Reverse of the given string is : sediugavaj