Retrieve the Users below a certain Role in Role Hierarchy #inSalesforce

Retrieve the Users below a certain Role in Role Hierarchy #inSalesforce

public with sharing class theRoleRetrieve {
    public static Set<ID> getUnderneathRole(Id userId) {
        Id roleId = [SELECT UserRoleId From User Where Id = :userId].UserRoleId;
        Set<Id> underneathRoleIds = getunderneathRoleIds(New Set<ID>{roleId});
        Map<Id, User> users = new Map<Id, User>([SELECT Id, Name From User Where UserRoleId IN :underneathRoleIds]);
        return users.keySet();
    }
    private static Set<ID> getunderneathRoleIds(Set<ID> roleIds) {
        Set<ID> mainRoleIds = new Set<ID>();
        for(UserRole userRole :[SELECT Id from UserRole Where ParentRoleId IN :roleIds AND ParentRoleID != null]){
            mainRoleIds.add(userRole.Id);
        }
        if(mainRoleIds.size() > 0){
            mainRoleIds.addAll(getunderneathRoleIds(mainRoleIds));
        }        
        return mainRoleIds;   
    }
}

Test by calling the above method may be in anonymous window:

Id userId = UserInfo.getUserId();
Set<Id> underneathRoles = theRoleRetrieve.getUnderneathRole(userId);
system.debug('!!!!!!!!!!underneathRoles!!!!!!!!!!!'+underneathRoles);