解决警告：Unchecked assignment java util HashSet to java util Set java lang String Unchecked call

<!--代码内容-->
@Override
public Set<String> findPermissions(String username) {
    //TODO 此处可以优化，比如查询到role后，一起获取roleId，然后直接根据roleId获取即可
    String sql = "select permission from sys_users u, sys_roles r, sys_permissions p, sys_users_roles ur, sys_roles_permissions rp where u.username=? and u.id=ur.user_id and r.id=ur.role_id and r.id=rp.role_id and p.id=rp.permission_id";
    return new HashSet(jdbcTemplate.queryForList(sql, String.class, username));
}

<!--这一句有警告-->
 return new HashSet(jdbcTemplate.queryForList(sql, String.class, username));

<!--警告内容-->
Unchecked assignment: 'java.util.HashSet' to 'java.util.Set'. Unchecked call to 'HashSet(Collection)' as a member of raw type 'java.util.HashSet'. 

上百度查询，无果

上Stack Overflow查询，给出的答案是如何让idea不再警告

这显然不是我想要的答案，面对警告肯定有解决的办法，而不是掩盖警告，这不是掩耳盗铃么
查询了一堆关于泛型相关的文章之后，决定拆开来写：

    @Override
public Set<String> findPermissions(String username) {
    //TODO 此处可以优化，比如查询到role后，一起获取roleId，然后直接根据roleId获取即可
    String sql = "select permission from sys_users u, sys_roles r, sys_permissions p, sys_users_roles ur, sys_roles_permissions rp where u.username=? and u.id=ur.user_id and r.id=ur.role_id and r.id=rp.role_id and p.id=rp.permission_id";
    List<String> list = jdbcTemplate.queryForList(sql, String.class, username;
    Set<String> set = new HashSet<>(list);
    return set;
}

<!--关键代码：-->

List<String> list = jdbcTemplate.queryForList(sql, String.class, username;
Set<String> set = new HashSet<>(list);
return set;

原来仅仅是少写了一对尖括号<>

同样的还有：

  List<User> userList = jdbcTemplate.query(sql, new BeanPropertyRowMapper(User.class), username);
  
<!--改为：-->

  List<User> userList = jdbcTemplate.query(sql, new BeanPropertyRowMapper<>(User.class), username);