lintcode-medium-Simplify Path

public class Solution {
    /**
     * @param path the original path
     * @return the simplified path
     */
    public String simplifyPath(String path) {
        // Write your code here
        
        if(path == null || path.length() == 0)
            return path;
        
        Stack<String> stack = new Stack<String>();
        
        int i = 0;
        int j = 1;
        int len = path.length();
        
        while(j < len){
            
            while(j < len && path.charAt(j) != ‘/‘)
                j++;
            
            String temp = path.substring(i, j);
            
            if(temp.equals("/.") || temp.equals("/")){
                i = j;
                j++;
            }
            else if(temp.equals("/..")){
                if(!stack.isEmpty())
                    stack.pop();
                
                i = j;
                j++;
            }
            else{
                stack.push(temp);
                i = j;
                j++;
            }
        }
        
        if(stack.isEmpty())
            return "/";
        
        String res = "";
        
        while(!stack.isEmpty()){
            res = stack.pop() + res;
        }
        
        return res;
    }
}