import java.util.*;

public class EncodeDecodeStrings {

public static void main(String[] args) {

EncodeDecodeStrings ed = new EncodeDecodeStrings();

String encoded = ed.encode(new ArrayList(Arrays.asList("0")));

System.out.println(encoded);

List<String> decoded = ed.decode(encoded);

System.out.println(decoded);

}

// Encodes a list of strings to a single string.

public String encode(List<String> strs) {

StringBuilder sb = new StringBuilder();

for(String s: strs) {

int len = s.length();

sb.append(Integer.toString(len));

sb.append('#');

sb.append(s);

}

return sb.toString();

}

// Decodes a single string to a list of strings.

public List<String> decode(String s) {

int i = 0;

List<String> parsed = new ArrayList<> ();

if(s.equals("")) return parsed;

while(i < s.length()) {

int markIdx = s.indexOf('#', i);

String lenStr = s.substring(i, markIdx);

int len = Integer.parseInt(lenStr);

String word = s.substring(markIdx + 1, markIdx + len + 1);

parsed.add(word);

i = markIdx + len + 1;

}

return parsed;

}

}