private Set<Role> roles = new HashSet<Role>(0); 解释一上用法

private Set<Role> roles = new HashSet<Role>(0); 解释一下用法？
private Set<Role> roles = new HashSet<Role>(0); 解释一下用法？

[解决办法]

Java code

        Set<Role> roles = new HashSet<Role>(0);        roles.add("a");        Iterator<Role> i = roles.iterator();        while (i.hasNext()) {            Role r = i.next();            System.out.println(r);        }