how to check certain checkboxes by default in spring boot

i am using spring boot in my project, and i am generating checkboxes using following approach.everything works fine but how can i check certain checkboxes.

 <form:checkboxes items="${availabilities}" `path="availabilities"  itemValue="idavailability" itemLabel="availabletype"` />

this is the controller method

public String approveContent( Model model){
        model.addAttribute("availabilities",availabilityRep.findAll());
        return "approve";
    }

this is the model

public class Availability implements Serializable {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int idavailability;

    private String availabletype;
}