Refactor avoid late keyword as much as possible

lib/src/excel.dart

@@ -23,31 +23,31 @@ Excel _newExcel(Archive archive) {
 
 /// Decode a excel file.
 class Excel {
-  late bool _styleChanges;
-  late bool _mergeChanges;
-  late bool _rtlChanges;
-
-  late Archive _archive;
-
-  late Map<String, XmlNode> _sheets;
-  late Map<String, XmlDocument> _xmlFiles;
-  late Map<String, String> _xmlSheetId;
-  late Map<String, Map<String, int>> _cellStyleReferenced;
-  late Map<String, Sheet> _sheetMap;
-
-  late List<CellStyle> _cellStyleList;
-  late List<String> _patternFill;
-  late List<String> _mergeChangeLook;
-  late List<String> _rtlChangeLook;
-  late List<_FontStyle> _fontStyleList;
-  late List<int> _numFmtIds;
-  late NumFormatMaintainer _numFormats = NumFormatMaintainer();
-  late List<_BorderSet> _borderSetList;
-
-  late _SharedStringsMaintainer _sharedStrings;
-
-  late String _stylesTarget;
-  late String _sharedStringsTarget;
+  bool _styleChanges = false;
+  bool _mergeChanges = false;
+  bool _rtlChanges = false;
+
+  Archive _archive;
+
+  final Map<String, XmlNode> _sheets = {};
+  final Map<String, XmlDocument> _xmlFiles = {};
+  final Map<String, String> _xmlSheetId = {};
+  final Map<String, Map<String, int>> _cellStyleReferenced = {};
+  final Map<String, Sheet> _sheetMap = {};
+
+  List<CellStyle> _cellStyleList = [];
+  List<String> _patternFill = [];
+  final List<String> _mergeChangeLook = [];
+  final List<String> _rtlChangeLook = [];
+  List<_FontStyle> _fontStyleList = [];
+  final List<int> _numFmtIds = [];
+  final NumFormatMaintainer _numFormats = NumFormatMaintainer();
+  List<_BorderSet> _borderSetList = [];
+
+  _SharedStringsMaintainer _sharedStrings = _SharedStringsMaintainer._();
+
+  String _stylesTarget = '';
+  String _sharedStringsTarget = '';
   String get _absSharedStringsTarget {
     if (_sharedStringsTarget.isNotEmpty && _sharedStringsTarget[0] == "/") {
       return _sharedStringsTarget.substring(1);
@@ -58,26 +58,7 @@ class Excel {
   String? _defaultSheet;
   late Parser parser;
 
-  Excel._(Archive archive) {
-    _styleChanges = false;
-    _mergeChanges = false;
-    _rtlChanges = false;
-    _sheets = <String, XmlNode>{};
-    _xmlFiles = <String, XmlDocument>{};
-    _xmlSheetId = <String, String>{};
-    _cellStyleReferenced = <String, Map<String, int>>{};
-    _sheetMap = <String, Sheet>{};
-    _cellStyleList = <CellStyle>[];
-    _patternFill = <String>[];
-    _mergeChangeLook = <String>[];
-    _rtlChangeLook = <String>[];
-    _fontStyleList = <_FontStyle>[];
-    _numFmtIds = <int>[];
-    _stylesTarget = '';
-    _sharedStringsTarget = '';
-
-    _archive = archive;
-    _sharedStrings = _SharedStringsMaintainer._();
+  Excel._(this._archive) {
     parser = Parser._(this);
     parser._startParsing();
   }

lib/src/parser/parse.dart

@@ -1,14 +1,11 @@
 part of excel;
 
 class Parser {
-  late Excel _excel;
-  late List<String> _rId;
-  late Map<String, String> _worksheetTargets;
-  Parser._(Excel excel) {
-    this._excel = excel;
-    this._rId = <String>[];
-    this._worksheetTargets = <String, String>{};
-  }
+  final Excel _excel;
+  final List<String> _rId = [];
+  final Map<String, String> _worksheetTargets = {};
+
+  Parser._(this._excel);
 
   void _startParsing() {
     _putContentXml();

lib/src/save/save_file.dart

@@ -2,13 +2,11 @@ part of excel;
 
 class Save {
   final Excel _excel;
-  late Map<String, ArchiveFile> _archiveFiles;
-  late List<CellStyle> _innerCellStyle;
+  final Map<String, ArchiveFile> _archiveFiles = {};
+  final List<CellStyle> _innerCellStyle = [];
   final Parser parser;
-  Save._(this._excel, this.parser) {
-    _archiveFiles = <String, ArchiveFile>{};
-    _innerCellStyle = <CellStyle>[];
-  }
+
+  Save._(this._excel, this.parser);
 
   void _addNewColumn(XmlElement columns, int min, int max, double width) {
     columns.children.add(XmlElement(XmlName('col'), [
@@ -172,7 +170,7 @@ class Save {
   /// Writing Font Color in [xl/styles.xml] from the Cells of the sheets.
 
   void _processStylesFile() {
-    _innerCellStyle = <CellStyle>[];
+    _innerCellStyle.clear();
     List<String> innerPatternFill = <String>[];
     List<_FontStyle> innerFontStyle = <_FontStyle>[];
     List<_BorderSet> innerBorderSet = <_BorderSet>[];

lib/src/sharedStrings/shared_strings.dart

@@ -55,10 +55,9 @@ class _SharedStringsMaintainer {
 
 class _IndexingHolder {
   final int index;
-  late int count;
-  _IndexingHolder(this.index, [int _count = 1]) {
-    this.count = _count;
-  }
+  int count;
+
+  _IndexingHolder(this.index, [int _count = 1]) : count = _count;
 
   void increaseCount() {
     this.count += 1;

lib/src/sheet/border_style.dart

@@ -1,15 +1,14 @@
 part of excel;
 
 class Border extends Equatable {
-  late final BorderStyle? borderStyle;
-  late final String? borderColorHex;
+  final BorderStyle? borderStyle;
+  final String? borderColorHex;
 
-  Border({BorderStyle? borderStyle, ExcelColor? borderColorHex}) {
-    this.borderStyle = borderStyle == BorderStyle.None ? null : borderStyle;
-    this.borderColorHex = borderColorHex != null
-        ? _isColorAppropriate(borderColorHex.colorHex)
-        : null;
-  }
+  Border({BorderStyle? borderStyle, ExcelColor? borderColorHex})
+      : borderStyle = borderStyle == BorderStyle.None ? null : borderStyle,
+        borderColorHex = borderColorHex != null
+            ? _isColorAppropriate(borderColorHex.colorHex)
+            : null;
 
   @override
   String toString() {
@@ -24,13 +23,13 @@ class Border extends Equatable {
 }
 
 class _BorderSet extends Equatable {
-  late final Border leftBorder;
-  late final Border rightBorder;
-  late final Border topBorder;
-  late final Border bottomBorder;
-  late final Border diagonalBorder;
-  late final bool diagonalBorderUp;
-  late final bool diagonalBorderDown;
+  final Border leftBorder;
+  final Border rightBorder;
+  final Border topBorder;
+  final Border bottomBorder;
+  final Border diagonalBorder;
+  final bool diagonalBorderUp;
+  final bool diagonalBorderDown;
 
   _BorderSet({
     required this.leftBorder,

lib/src/sheet/sheet.dart

@@ -1,20 +1,20 @@
 part of excel;
 
 class Sheet {
-  late Excel _excel;
-  late String _sheet;
-  late bool _isRTL;
-  late int _maxRows;
-  late int _maxColumns;
+  final Excel _excel;
+  final String _sheet;
+  bool _isRTL = false;
+  int _maxRows = 0;
+  int _maxColumns = 0;
   double? _defaultColumnWidth;
   double? _defaultRowHeight;
   Map<int, double> _columnWidths = {};
   Map<int, double> _rowHeights = {};
   Map<int, bool> _columnAutoFit = {};
-  late FastList<String> _spannedItems;
-  late List<_Span?> _spanList;
-  late Map<int, Map<int, Data>> _sheetData;
-  late HeaderFooter? _headerFooter;
+  FastList<String> _spannedItems = FastList<String>();
+  List<_Span?> _spanList = [];
+  Map<int, Map<int, Data>> _sheetData = {};
+  HeaderFooter? _headerFooter;
 
   ///
   /// It will clone the object by changing the `this` reference of previous oldSheetObject and putting `new this` reference, with copying the values too
@@ -32,7 +32,7 @@ class Sheet {
             isRTLVal: oldSheetObject._isRTL,
             headerFooter: oldSheetObject._headerFooter);
 
-  Sheet._(Excel excel, String sheetName,
+  Sheet._(this._excel, this._sheet,
       {Map<int, Map<int, Data>>? sh,
       List<_Span?>? spanL_,
       FastList<String>? spanI_,
@@ -43,14 +43,6 @@ class Sheet {
       Map<int, double>? rowHeightsVal,
       Map<int, bool>? columnAutoFitVal,
       HeaderFooter? headerFooter}) {
-    _excel = excel;
-    _sheet = sheetName;
-    _sheetData = <int, Map<int, Data>>{};
-    _spanList = <_Span?>[];
-    _spannedItems = FastList<String>();
-    _isRTL = false;
-    _maxRows = 0;
-    _maxColumns = 0;
     _headerFooter = headerFooter;
 
     if (spanL_ != null) {

test/excel_test.dart

@@ -558,7 +558,7 @@ void main() {
       var file = './test/test_resources/example.xlsx';
       var bytes = File(file).readAsBytesSync();
       var excel = Excel.decodeBytes(bytes);
-      Sheet? sheetObject = excel.tables['Sheet1']!;
+      Sheet sheetObject = excel.tables['Sheet1']!;
 
       sheetObject.headerFooter!.oddHeader = "Foo";
       sheetObject.headerFooter!.oddFooter = "Bar";