Format of data storage

what is the format of edge binary file ? is there any detail doc about graphhopper-core-0.8.2 ?

There is some older documentation about it here: https://github.com/graphhopper/graphhopper/blob/master/docs/core/technical.md

Q:

  1. this is a directed graph ?
  2. One 'node row' consists of latitude,longitude (not shown) and the first edgeID
    which is the firat Edge ? in or out edge ?
  3. edge A-A (Self-Loop edge) isvalid?
  4. from node 0, first get edge 0-3, if i want to get edge about 0 , so I should traverse from nextA(because node 0 is at nodeA)? is that ??

this is a directed graph

yes

One ‘node row’ consists of latitude,longitude (not shown) and the first edgeID which is the firat Edge ? in or out edge ?

yes, and optionally some more like elevation and turn cost information, see BaseGraph.java. The node property indices are annotated via N_SOMETHING and the edge properties are like E_SOMETHING, for edge properties also look into EdgeAccess

edge A-A (Self-Loop edge) isvalid?

no

from node 0, first get edge 0-3, if i want to get edge about 0 , so I should traverse from nextA(because node 0 is at nodeA)? is that ??

yes, this is correct

the edge 0-3 ; from 0 to 3 or from 3 to 0, how can i find this ?

Have a look here via the normal graph exploration: Change dynamically direction of edge and see GHUtility.getEdge on how to use this