Java有內建Stack Class，很方便。
package exercise;
import java.util.Stack;
public class Ex01 {
public static void main(String[] args) {
Stack<Character> stack = new Stack<Character>();
String input = "123456";
int length = input.length();
for(int i=0; i<length; i++)
{
char x = input.charAt( i );
stack.push(new Character( x ));
}
while(!stack.empty())
{
Character ch = stack.pop();
System.out.println(ch);
}
}
}
