/**
 * Expands a string s to have the length l
 * @param s the String to expand
 * @param l the length of the desired String
 * @return s, copied until it has length l
 */
public static String expand(String s, int l) {
    String ret = new String(s);

    while(ret.length() < l) {
        ret += ret;
    }

    if(ret.length() > l) {
        ret = ret.substring(0, l);
    }

    return ret;
}