Program: 54007
Project: 54007
Buggy source:
public ServerCallTree build(){
  if (isBuilt)   return this;
  for (  Entry<String,TerminalRequest> entry : terminalRequests.entrySet()) {
    TerminalRequest terminal=entry.getValue();
    Server server=new Server(terminal.getTo(),terminal.getTo(),"String_Node_Str",ServiceType.parse(terminal.getToServiceType()));
    servers.put(server.getId(),server);
  }
  int i=0;
  for (  Entry<String,Server> entry : servers.entrySet()) {
    entry.getValue().setSequence(i++);
  }
  for (  Entry<String,TerminalRequest> entry : terminalRequests.entrySet()) {
    TerminalRequest terminal=entry.getValue();
    ServerRequest request=new ServerRequest(servers.get(terminal.getFrom()),servers.get(terminal.getTo()),terminal.getStatistics().getHistogram());
    serverRequests.put(request.getId(),request);
  }
  for (  SpanBo span : spans) {
    String from=String.valueOf(span.getParentSpanId());
    String to=String.valueOf(span.getSpanId());
    Server fromServer=servers.get(spanIdToServerId.get(from));
    Server toServer=servers.get(spanIdToServerId.get(to));
    if (fromServer == null) {
      fromServer=servers.get(spanIdToServerId.get(PREFIX_CLIENT + to));
    }
    if (fromServer == null) {
      logger.debug("String_Node_Str",from);
      continue;
    }
    ServerRequest serverRequest=new ServerRequest(fromServer,toServer);
    if (serverRequest.isSelfCalled()) {
      continue;
    }
    if (serverRequests.containsKey(serverRequest.getId())) {
      serverRequests.get(serverRequest.getId()).addRequest(span.getElapsed());
    }
 else {
      serverRequests.put(serverRequest.getId(),serverRequest);
    }
  }
  isBuilt=true;
  return this;
}

Fixed version (ground truth):
public ServerCallTree build(){
  if (isBuilt)   return this;
  for (  Entry<String,TerminalRequest> entry : terminalRequests.entrySet()) {
    TerminalRequest terminal=entry.getValue();
    Server server=new Server(terminal.getTo(),terminal.getTo(),"String_Node_Str",ServiceType.parse(terminal.getToServiceType()),terminal.getStatistics().getAgentIds());
    servers.put(server.getId(),server);
  }
  int i=0;
  for (  Entry<String,Server> entry : servers.entrySet()) {
    entry.getValue().setSequence(i++);
  }
  for (  Entry<String,TerminalRequest> entry : terminalRequests.entrySet()) {
    TerminalRequest terminal=entry.getValue();
    ServerRequest request=new ServerRequest(servers.get(terminal.getFrom()),servers.get(terminal.getTo()),terminal.getStatistics().getHistogram());
    serverRequests.put(request.getId(),request);
  }
  for (  SpanBo span : spans) {
    String from=String.valueOf(span.getParentSpanId());
    String to=String.valueOf(span.getSpanId());
    Server fromServer=servers.get(spanIdToServerId.get(from));
    Server toServer=servers.get(spanIdToServerId.get(to));
    if (fromServer == null) {
      fromServer=servers.get(spanIdToServerId.get(PREFIX_CLIENT + to));
    }
    if (fromServer == null) {
      logger.debug("String_Node_Str",from);
      continue;
    }
    ServerRequest serverRequest=new ServerRequest(fromServer,toServer);
    if (serverRequest.isSelfCalled()) {
      continue;
    }
    if (serverRequests.containsKey(serverRequest.getId())) {
      serverRequests.get(serverRequest.getId()).addRequest(span.getElapsed());
    }
 else {
      serverRequests.put(serverRequest.getId(),serverRequest);
    }
  }
  isBuilt=true;
  return this;
}