java initialize object from file

Question

I am currently writing a program that deals with graphs created by the jgrapht library. I have multiple graphs of the form:

UndirectedGraph <Integer, DefaultEdge> g_x = new SimpleGraph<Integer, DefaultEdge (DefaultEdge.class);
g.addVertex(1);
g.addVertex(2);
g.addVertex(3);
g.addEdge(1, 2);
g.addEdge(2, 4);
...

which are constant graphs associated with street maps that I am given as files. Right now I have all of my graphs declared in my main method and just reference the graph I want when a map is loaded. What I would like to do is have another file paired with each map (i.e map1.map and map1.graph) so that when I load the map from a file I can also load the graph like:

map = loadMap(mapName);
g_x = loadGraph(mapName);

where mapName is the file name prefix and not have to store it in my source code. Is it possible to do this in java and if so how would I create the files and load them? Would it also be possible to do this with a generic Object?

Answer 1

One option is to serialize your objects to xml or json (you could change the .xml to .map if you really wanted). Then you can open the xml in your code for each object you wish to load.

Serializing:

File file = new File(**filename**);
FileOutputStream out = new FileOutputStream(file);
XStream xmlStream = new XStream(new DomDriver());
out.write(xmlStream.toXML(**ObjectToSave**).getBytes());
out.close();

Deserializing:

 try {
     XStream xmlStream = new XStream(new DomDriver());
     state = (**ClassNameYouWishToSave**) xmlStream.fromXML(new FileInputStream(**filename**));
 } catch(IOException e) { e.printStackTrace(); }

You will need these imports:

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

It is a simplistic way to do it, but it works. Hope it helps.