Using java, input string="aabbcdeaaaabbb" and the output must be aaaa -

using java, input string="aabbcdeaaaabbb" , output must aaaa, sequence here having repeated 4 times a. can me "aaaa" output using java implementation.

algorithm find longest substring having same character repeated.

for eg:

i/p: aabbcdefaaaacccccc o/p: cccccc

please check program below , suggest optimization faster processing:

public class longestsubstring { public static void main(string[] args) throws ioexception {  bufferedreader reader = new bufferedreader(new inputstreamreader(         system.in)); system.out         .println("enter word find longest substring same characters repeated"); string word = reader.readline();  system.out.println("entered word is: " + word);  system.out.println("longest repeated characters substring is: "         + substringfinder(word));  }  /* *longest substring finder same character repeated */  public static string substringfinder(string word) { char[] tokens = word.tochararray(); int len = tokens.length; int wordlen = word.length();  system.out.println("len of input word: " + wordlen);  list<string> mylist = new arraylist<>(); stringbuilder strconcat = new stringbuilder(""); (int j = 0; j <= len - 1; j++) {      if (j + 1 > len - 1) {         if ((strconcat.length() >= 1)                 && (strconcat.charat(strconcat.length() - 1) == (tokens[j]))) {             strconcat.append("" + tokens[j]);             mylist.add(strconcat.tostring());         }     }      else {         if (tokens[j] == tokens[j + 1]) {             if ((strconcat.length() >= 1)                     && (strconcat.charat(strconcat.length() - 1) == (tokens[j]))) {                 strconcat.append("" + tokens[j]);                 mylist.add(strconcat.tostring());             } else {                 strconcat = new stringbuilder("");                 strconcat.append("" + tokens[j]);             }         } else {             if ((strconcat.length() >= 1)                     && (strconcat.charat(strconcat.length() - 1) == (tokens[j]))) {                 strconcat.append("" + tokens[j]);                 mylist.add(strconcat.tostring());             } else {                 strconcat = new stringbuilder("");                 strconcat.append("" + tokens[j]);             }         }     } }  int max = 0, index = 0; (int = 0; < mylist.size(); i++) {     string strele = mylist.get(i);     int strlen = strele.length();      if (max < strlen) {         max = strlen;         index = i;     }  }  return mylist.get(index);  } } 

i believe code overly complicated. don’t need stringbuilder nor arraylist. tried understand intention, skipped , wrote own version instead. hope helps anyway.

public static string substringfinder(string word) {     if (word == null || word.isempty()) {         return word;     }     char currentchar = word.charat(0);     int longeststart = 0;     int longestlength = 0;     int currentstart = 0;     int currentlength = 1;     (int ix = 1; ix < word.length(); ix++) {         if (word.charat(ix) == currentchar) {             currentlength++;         } else {             if (currentlength > longestlength) {                 longeststart = currentstart;                 longestlength = currentlength;             }             currentchar = word.charat(ix);             currentstart = ix;             currentlength = 1;         }     }     if (currentlength > longestlength) {         longeststart = currentstart;         longestlength = currentlength;     }     return word.substring(longeststart, longeststart + longestlength); }