Program: 96423
Project: 96423
Buggy source:
/** 
 * validate the input
 */
@Override protected boolean doCheckState(){
  String value=getStringValue();
  if (value != null && value.trim().length() > 0) {
    int offset=0;
    Iterator<CssRule> ruleIterator=cssStyleManager.createRuleIterator(value);
    while (ruleIterator.hasNext()) {
      CssRule rule=ruleIterator.next();
      if (rule.offset > offset) {
        String gap=value.substring(offset,rule.offset);
        if (gap.trim().length() != 0) {
          setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),gap.trim(),offset));
          return false;
        }
      }
      offset=rule.offset + rule.length;
      if (!rule.knownRule) {
        StringBuilder recognizedNames=new StringBuilder();
        for (        String recognizedName : cssStyleManager.getRecognizedRuleNames()) {
          if (recognizedNames.length() > 0) {
            recognizedNames.append(Messages.getString("String_Node_Str"));
          }
          recognizedNames.append(recognizedName);
        }
        setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),rule.name,recognizedNames));
        return false;
      }
      if (CssStyleManager.RULE_COLOR.equals(rule.name) || CssStyleManager.RULE_BACKGROUND_COLOR.equals(rule.name)) {
        Integer rgb=CssStyleManager.cssColorRgb(rule.value);
        if (rgb == null) {
          setErrorMessage(MessageFormat.format("String_Node_Str",rule.value));
          return false;
        }
      }
    }
    if (offset < value.length() - 1) {
      String gap=value.substring(offset,value.length());
      if (gap.trim().length() != 0) {
        setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),gap.trim(),offset));
        return false;
      }
    }
  }
  return super.doCheckState();
}

Fixed version (ground truth):
/** 
 * validate the input
 */
@Override protected boolean doCheckState(){
  String value=getStringValue();
  if (value != null && value.trim().length() > 0) {
    int offset=0;
    Iterator<CssRule> ruleIterator=cssStyleManager.createRuleIterator(value);
    while (ruleIterator.hasNext()) {
      CssRule rule=ruleIterator.next();
      if (rule.offset > offset) {
        String gap=value.substring(offset,rule.offset);
        if (gap.trim().length() != 0) {
          setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),gap.trim(),offset));
          return false;
        }
      }
      offset=rule.offset + rule.length;
      if (!rule.knownRule) {
        StringBuilder recognizedNames=new StringBuilder();
        for (        String recognizedName : cssStyleManager.getRecognizedRuleNames()) {
          if (recognizedNames.length() > 0) {
            recognizedNames.append(Messages.getString("String_Node_Str"));
          }
          recognizedNames.append(recognizedName);
        }
        setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),rule.name,recognizedNames));
        return false;
      }
      if (CssStyleManager.RULE_COLOR.equals(rule.name) || CssStyleManager.RULE_BACKGROUND_COLOR.equals(rule.name)) {
        Integer rgb=CssStyleManager.cssColorRgb(rule.value);
        if (rgb == null) {
          setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),rule.value));
          return false;
        }
      }
    }
    if (offset < value.length() - 1) {
      String gap=value.substring(offset,value.length());
      if (gap.trim().length() != 0) {
        setErrorMessage(MessageFormat.format(Messages.getString("String_Node_Str"),gap.trim(),offset));
        return false;
      }
    }
  }
  return super.doCheckState();
}