public static long string2long(String s,int radix) throws NumberFormatException {
  if (radix == 10) {
    return Long.parseLong(s,radix);
  }
 else {
    char[] cs=s.toCharArray();
    long limit=Long.MAX_VALUE / (radix / 2);
    long n=0;
    for (int i=0; i < cs.length; i++) {
      int d=Character.digit(cs[i],radix);
      if (n < 0 || n > limit || n * radix > Long.MAX_VALUE - d)       throw new NumberFormatException();
      n=n * radix + d;
    }
    return n;
  }
}

public static long string2long ( String s , int radix ) throws NumberFormatException { if ( radix == 10 ) { return Long . parseLong ( s , radix ) ; } else { char [ ] cs = s . toCharArray ( ) ; long limit = Long . MAX_VALUE / ( radix / 2 ) ; long n = 0 ; for ( int i = 0 ; i < cs . length ; i ++ ) { int d = Character . digit ( cs [ i ] , radix ) ; if ( n < 0 || n > limit || n * radix > Long . MAX_VALUE - d ) throw new NumberFormatException ( ) ; n = n * radix + d ; } return n ; } }
convert string to long integer .
