How to set defalult selected items in selectOneRadio/selectCheckboxMenu by beans in primefaces

I want to create selectOneRadio list and selectCheckboxMenu which items get from related bean objects. For non selected list it is working well.But how can i provide these lists with some item(s) selected by default. My current selectCheckboxMenu code is like this.

<p:selectCheckboxMenu id="trdays" 
             value="#{mybean.selectedDay}"
             label="Select Days">
      <f:selectItems value="#{mybean.dayList}" var="day"
       itemValue="#{day.value}" itemLabel="#{day.name}"/>
</p:selectCheckboxMenu>

it should look like this when page loaded and user haven't done anything yet.

EDIT Day Class :-

public class Day{

  private String name;
  private String value;

  //getters and setters

}

Value attribute of selectCheckboxMenu component should get the your default values. On bean side you should write a getter for selectedDayList and all daylist.

Example:

@PostConstruct
public void init() {
            dayList= new ArrayList<String>();
            dayList.add("Mon");
            dayList.add("Tue");
            dayList.add("Wed");
            dayList.add("Thu");
            dayList.add("Fri");
            dayList.add("Sat");
            dayList.add("Sun");

            selectedDayList= new ArrayList<String>();
            selectedDayList.add("Tue");
            selectedDayList.add("Wed");
}


public List<String> getDayList()
    {
        return dayList;
    }

public List<String> getSelectedDaylist()
    {
        return selectedDayList;
    }

.xhtml page should be like this.

<p:selectCheckboxMenu id="trdays" 
             value="#{mybean.selectedDaylist}"
             label="Select Days">
      <f:selectItems value="#{mybean.dayList}" var="day"
       itemValue="#{day.value}" itemLabel="#{day.name}"/>
</p:selectCheckboxMenu>

Good Luck!