title: How compare strings in ConditionalFormatting?
body: <p>The following code works perfectly and background changes when you change the data:</p>
  
  <pre><code>constraint = validationHelper.createExplicitListConstraint(new String[]{"10","11"});
  
  XSSFSheetConditionalFormatting my_cond_format_layer = sheet.getSheetConditionalFormatting();    
  XSSFConditionalFormattingRule my_rule = my_cond_format_layer.createConditionalFormattingRule(ComparisonOperator.EQUAL,"10");
  
  PatternFormatting fill1 = my_rule.createPatternFormatting();
  fill1.setFillBackgroundColor(IndexedColors.GREEN.index);
  fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
  
  CellRangeAddress[] my_data_range = {CellRangeAddress.valueOf("C1:C90")};
  my_cond_format_layer.addConditionalFormatting(my_data_range,my_rule);
  
  XSSFSheetConditionalFormatting my_cond_format_layer2 = sheet.getSheetConditionalFormatting();
  XSSFConditionalFormattingRule my_rule2 = my_cond_format_layer2.createConditionalFormattingRule(ComparisonOperator.EQUAL,"11");
  
  PatternFormatting fill12 = my_rule2.createPatternFormatting();
  fill12.setFillBackgroundColor(IndexedColors.RED.index);
  fill12.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
  
  CellRangeAddress[] my_data_range2 = {CellRangeAddress.valueOf("C1:C90")};     
  my_cond_format_layer.addConditionalFormatting(my_data_range2,my_rule2);
  </code></pre>
  
  <p>While the following doesn't work and background doesn't change: </p>
  
  <pre><code>constraint = validationHelper.createExplicitListConstraint(new String[]{"OK","ERROR"});
  
  XSSFSheetConditionalFormatting my_cond_format_layer = sheet.getSheetConditionalFormatting();         
  XSSFConditionalFormattingRule my_rule = my_cond_format_layer.createConditionalFormattingRule(ComparisonOperator.EQUAL,"OK");
  
  PatternFormatting fill1 = my_rule.createPatternFormatting();
  fill1.setFillBackgroundColor(IndexedColors.GREEN.index);
  fill1.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
  
  CellRangeAddress[] my_data_range = {CellRangeAddress.valueOf("C1:C90")};     
  my_cond_format_layer.addConditionalFormatting(my_data_range,my_rule);
  
  XSSFSheetConditionalFormatting my_cond_format_layer2 = sheet.getSheetConditionalFormatting();
  XSSFConditionalFormattingRule my_rule2 = my_cond_format_layer2.createConditionalFormattingRule(ComparisonOperator.EQUAL,"ERROR");
  
  PatternFormatting fill12 = my_rule2.createPatternFormatting();
  fill12.setFillBackgroundColor(IndexedColors.RED.index);
  fill12.setFillPattern(PatternFormatting.SOLID_FOREGROUND);
  
  CellRangeAddress[] my_data_range2 = {CellRangeAddress.valueOf("C1:C90")};  
  my_cond_format_layer.addConditionalFormatting(my_data_range2,my_rule2);
  </code></pre>
  
  <p>Can you please advise what's the problem here? I went through the documentation and couldn't find a problem.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>Finally i discover the problem, when I open the excel and i check the conditional format I see that POI or Excel  is inserting an equal after the string <code>ok</code> or <code>error</code>, something like this <code>=ok</code> and <code>=error</code>. If I manually in the excel remove the equal it works perfectly and the cell background change when the data validation list change.</p>
  
  <p>Now the new question is, how can I remove the equal from the code? or what's the right way to compare strings in Apache POI with conditional formatting?</p>