question: public static final int parseInt ( char [ ] array , int start , int length ) throws NumberFormatException { if ( length == 1 ) { int result = array [ start ] - '0' ; if ( result < 0 || result > 9 ) { throw new NumberFormatException ( "invalid digit" ) ; } return result ; } else { return Integer . parseInt ( new String ( array , start , length ) ) ; } }
target:  Return the int value represented by the designated subpart of array. The calculation of the result for single-digit positive integers is optimized in time.