Program: 11318
Project: 11318
Buggy source:
private <T extends Item>Collection<T> executeQuery(final AttributeQuery query,final Class<T> itemClass){
  final Map<ItemId,T> allItems=getAllItems(itemClass);
  final Collection<T> matches=new ArrayList<>();
  for (  final T item : allItems.values()) {
    final String attribute=query.getAttributeName();
    try {
      final Method getter=new PropertyDescriptor(attribute,item.getClass()).getReadMethod();
      final Object itemPropertyValue=getter.invoke(item);
      final Class<?> itemPropertyType=getter.getReturnType();
      final Condition condition=query.getCondition();
      final Set<String> values=condition.getValues();
      String singleValue=null;
      if (values != null && !values.isEmpty()) {
        singleValue=values.iterator().next();
      }
      final boolean isSingleItemProperty=!Collection.class.isAssignableFrom(itemPropertyType);
      String singleItemPropertyValue=null;
      if (isSingleItemProperty) {
        singleItemPropertyValue=String.valueOf(itemPropertyValue);
      }
switch (query.getCondition().getComparisonOperator()) {
case NULL:
        if (itemPropertyValue == null) {
          matches.add(item);
        }
      break;
case NOT_NULL:
    if (itemPropertyValue != null) {
      matches.add(item);
    }
  break;
case LESS_THAN_OR_EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.compareTo(singleValue) >= 0) {
  matches.add(item);
}
break;
case GREATER_THAN_OR_EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.compareTo(singleValue) <= 0) {
matches.add(item);
}
break;
case EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.equals(singleValue)) {
matches.add(item);
}
 else if (itemPropertyValue.equals(values)) {
matches.add(item);
}
break;
default :
break;
}
}
 catch (final Exception e) {
throw new IllegalStateException("String_Node_Str" + attribute + "String_Node_Str"+ item.getClass()+ "String_Node_Str");
}
}
return matches;
}

Fixed version (ground truth):
private <T extends Item>Collection<T> executeQuery(final AttributeQuery query,final Class<T> itemClass){
  final Map<ItemId,T> allItems=getAllItems(itemClass);
  final Collection<T> matches=new ArrayList<>();
  for (  final T item : allItems.values()) {
    final String attribute=query.getAttributeName();
    try {
      final Method getter=new PropertyDescriptor(attribute,item.getClass()).getReadMethod();
      final Object itemPropertyValue=getter.invoke(item);
      final Class<?> itemPropertyType=getter.getReturnType();
      final Condition condition=query.getCondition();
      final Set<String> values=condition.getValues();
      String singleValue=null;
      if (values != null && !values.isEmpty()) {
        singleValue=values.iterator().next();
      }
      final boolean isSingleItemProperty=!Collection.class.isAssignableFrom(itemPropertyType);
      String singleItemPropertyValue=null;
      if (isSingleItemProperty) {
        singleItemPropertyValue=String.valueOf(itemPropertyValue);
      }
switch (query.getCondition().getComparisonOperator()) {
case NULL:
        if (itemPropertyValue == null) {
          matches.add(item);
        }
      break;
case NOT_NULL:
    if (itemPropertyValue != null) {
      matches.add(item);
    }
  break;
case LESS_THAN_OR_EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.compareTo(singleValue) <= 0) {
  matches.add(item);
}
break;
case GREATER_THAN_OR_EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.compareTo(singleValue) >= 0) {
matches.add(item);
}
break;
case EQUALS:
if (isSingleItemProperty && singleItemPropertyValue.equals(singleValue)) {
matches.add(item);
}
 else if (values.equals(itemPropertyValue)) {
matches.add(item);
}
break;
default :
break;
}
}
 catch (final Exception e) {
e.printStackTrace();
throw new IllegalStateException("String_Node_Str" + attribute + "String_Node_Str"+ item.getClass()+ "String_Node_Str");
}
}
return matches;
}