code: public String getProcessTreeDump() {
      StringBuilder ret = new StringBuilder();
      // The header.
      ret.append(String.format("\t|- PID PPID PGRPID SESSID CMD_NAME "
          + "USER_MODE_TIME(MILLIS) SYSTEM_TIME(MILLIS) VMEM_USAGE(BYTES) "
          + "RSSMEM_USAGE(PAGES) FULL_CMD_LINE\n"));
      for (ProcessInfo p : processTree.values()) {
        if (p != null) {
          ret.append(String.format(PROCESSTREE_DUMP_FORMAT, p.getPid(), p
              .getPpid(), p.getPgrpId(), p.getSessionId(), p.getName(), p
              .getUtime(), p.getStime(), p.getVmem(), p.getRssmemPage(), p
              .getCmdLine(procfsDir)));
        }
      }
      return ret.toString();
    }
docs: Get a dump of the process-tree.
  
  @return a string concatenating the dump of information of all the processes
  in the process-tree