public class CheckParentheses {
   9      public boolean check(String input) {
  10          TrakStack a = new TrakStack();
  11          char L1 = '(';
  12          char L2 = '{';
  13          char L3 = '[';
  14          char R1 = ')';
  15          char R2 = '}';
  16          char R3 = ']';
  17          for (char current: input.toCharArray()){
  18              if (current == L1 || current == L2 || current == L3){
  19                  a.push(current);
  20              }
  21              if (current == R1){
  22                  if (a.pop() != L1){
  23                      return false;
  24                  }
  25              }
  26              if (current == R2){
  27                  if (a.pop() != L2){
  28                      return false;
  29                  }
  30              }
  31              if (current == R3){
  32                  if (a.pop() != L3){
  33                      return false;
  34                  }
  35              }
  36          }
  37          return true;
  38      }
  39
  40  }