question: protected final String _handleUnusualFieldName ( int i ) throws IOException , JsonParseException { if ( i == INT_APOSTROPHE && isEnabled ( Feature . ALLOW_SINGLE_QUOTES ) ) { return _parseApostropheFieldName ( ) ; } if ( ! isEnabled ( Feature . ALLOW_UNQUOTED_FIELD_NAMES ) ) { _reportUnexpectedChar ( i , "was expecting double-quote to start field name" ) ; } final int [ ] codes = CharTypes . getInputCodeLatin1JsNames ( ) ; final int maxCode = codes . length ; boolean firstOk ; if ( i < maxCode ) { firstOk = ( codes [ i ] == 0 ) && ( i < INT_0 || i > INT_9 ) ; } else { firstOk = Character . isJavaIdentifierPart ( ( char ) i ) ; } if ( ! firstOk ) { _reportUnexpectedChar ( i , "was expecting either valid name character (for unquoted name) or double-quote (for quoted) to start field name" ) ; } int ptr = _inputPtr ; int hash = 0 ; final int inputLen = _inputEnd ; if ( ptr < inputLen ) { do { int ch = _inputBuffer [ ptr ] ; if ( ch < maxCode ) { if ( codes [ ch ] != 0 ) { int start = _inputPtr - 1 ; _inputPtr = ptr ; return _symbols . findSymbol ( _inputBuffer , start , ptr - start , hash ) ; } } else if ( ! Character . isJavaIdentifierPart ( ( char ) ch ) ) { int start = _inputPtr - 1 ; _inputPtr = ptr ; return _symbols . findSymbol ( _inputBuffer , start , ptr - start , hash ) ; } hash = ( hash * 31 ) + ch ; ++ ptr ; } while ( ptr < inputLen ) ; } int start = _inputPtr - 1 ; _inputPtr = ptr ; return _parseUnusualFieldName2 ( start , hash , codes ) ; }
target:  Method called when we see non-white space character other than double quote, when expecting a field name. In standard mode will just throw an expection; but in non-standard modes may be able to parse name.