Here is some example java code:
String userName = "myusername;"
PermissionService permissionservice = serviceRegistry.getPermissionService();
permissionService.setPermission(nodeRef, userName, PermissionService.CONSUMER, true);
NodeRef dir = fileFolderService.searchSimple(nodeRef, userName);
if (dir == null){
dir = fileFolderService.create(nodeRef, userName, ContentModel.TYPE_FOLDER).getNodeRef();
permissionService.setInheritParentPermissions(dir, false);//should not be visible to others
permissionService.setPermission(dir, "GROUP_managers", PermissionService.COORDINATOR, true);
permissionService.setPermission(dir, "GROUP_basicusers", PermissionService.CONSUMER, true);
}
permissionService.setPermission(dir, userName, PermissionService.CONTRIBUTOR, true);