question: public boolean onlyLettersOrDigits ( final @ NonNull CharSequence input , final int numCharsToCheck , final int start ) { if ( start < 0 || start > input . length ( ) ) { return false ; } for ( int i = 0 ; i < numCharsToCheck ; i ++ ) { int positionToCheck = start + i ; if ( positionToCheck >= input . length ( ) ) { return false ; } char charToCheck = input . charAt ( positionToCheck ) ; if ( ! Character . isLetterOrDigit ( charToCheck ) ) { return false ; } } return true ; }
target:  Given a string and starting index, return true if the first "numCharsToCheck" characters at the starting index are either a letter or a digit.