Utility method that can traverse the Liferay Group hierarchy and build an array of long representing all child groups. Useful in scoping a searchContext for content in an org hierarchy.

GroupUtil-getCurrentAndChildGroups.java

public static long[] getCurrentAndChildGroupIds(Group currentGroup){
    try {
        List<Long> theseChildGroupIds = new ArrayList<>();
        theseChildGroupIds.add(currentGroup.getGroupId());
        for (Group childGroup : currentGroup.getChildren(true)
            ) {
            theseChildGroupIds.add(childGroup.getGroupId());
            if(childGroup.getChildren(true).size() > 0){
                for (Group grandChildGroup : childGroup.getChildren(true)
                    ) {
                    theseChildGroupIds.add(grandChildGroup.getGroupId());
                }
            }

        }

        Long[] l1 = theseChildGroupIds.toArray(new Long[theseChildGroupIds.size()]);
        long[] l2 = ArrayUtils.toPrimitive(l1);
        return l2;

        //log.debug("Current and Child GroupIds: " + ArrayUtils.toString(l2));

    } catch (SystemException e) {
        log.error(e.getMessage());
        return null;
    }
}