Encode and Decode Strings

Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.

Machine 1 (sender) has the function:

string encode(vector<string> strs) {
  // ... your code
  return encoded_string;
}
Machine 2 (receiver) has the function:
vector<string> decode(string s) {
  //... your code
  return strs;
}
So Machine 1 does:

string encoded_string = encode(strs);
and Machine 2 does:

vector<string> strs2 = decode(encoded_string);
strs2 in Machine 2 should be the same as strs in Machine 1.

Implement the encode and decode methods.

Format: length%{data}

public class Codec {

    public String encode(List<String> strs) {
        StringBuffer result = new StringBuffer();

        if(strs == null || strs.size() == 0)
            return result.toString();

        for(String str: strs){
            result.append(str.length());
            result.append("%");
            result.append(str);
        }

        return result.toString();
    }

    // Decodes a single string to a list of strings.
    public List<String> decode(String s) {
        List<String> result = new ArrayList();

        if(s == null || s.length() == 0)
            return result;

        int current = 0;
        while(true){
            if(current == s.length())
                break;
            StringBuffer sb = new StringBuffer();
            while(s.charAt(current) != '%'){
                sb.append(s.charAt(current));
                current++;
            }
            int len = Integer.parseInt(sb.toString());
            int end = current + 1 + len;
            result.add(s.substring(current+1, end));
            current = end;
        }
        return result;
    }
}