string - How to implement trim() method in java by using only substring() method -

i know question quite silly, in interview told implement trim() method without using method string class except substring() method.

i approached problem using tochararray() , identifying first , last valid character of string. told not use tochararray() method.

could suggest approach it.

overriden methods of objects class allowed equals() , hashcode().

string untrimmed = "    string   "; string trimmed = "";  string innerspaces = ""; boolean wordboundary = true;  try {     (int = 0; ; i++) {         string substr = untrimmed.substring(i, + 1);          if (!substr.equals(" ") && !substr.equals("\t") &&                 !substr.equals("\n") && !substr.equals("\r")) {              trimmed += innerspaces + substr;             wordboundary = false;             innerspaces = "";         }         else if (!wordboundary) {             innerspaces += substr;         }     } } catch (indexoutofboundsexception e)  { }  system.out.println(trimmed);