public boolean addLink(Link link) {
            Objects.requireNonNull(link, "link");

            final LinkKey linkId = link.getLinkKey();
            return this.linkMap.putIfAbsent(linkId, link) == null;
        }
find all out links of fromApplication
@param fromApplication
@return
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/link/LinkList.java