java - Writing and reading ListMultimap<Object, Object> in file -

i tried writing listmultimap file using properties, seems impossible, refer question writing , reading listmultimap file using properties.

going ahead, if using properties store listmultimap not correct way, how can store listmultimap file? , how can read file?

e.g. lets have:

listmultimap<object, object> index = arraylistmultimap.create(); 

how can write methods write listmultimap file , read file:

writetofile(listmultimap multimap, string filepath){     //?? }  listmultimap readfromfile(string filepath){     listmultimap multimap;     //multimap = read file     return multimap; } 

you need decide how represent each object in file. example, if listmultimap contained strings write string value if you're dealing complex objects need produce representation of object byte[], if want use properties should base64 encoded.

the basic read method should like:

public listmultimap<object, object> read(inputstream in) throws ioexception {   listmultimap<object, object> index = arraylistmultimap.create();    properties properties = new properties();   properties.load(in);    (object serializedkey : properties.keyset())     {     string deserializedkey = deserialize(serializedkey);     string values = properties.get(serializedkey);      (string value : values.split(","))      {       index.put(deserializedkey, deserialize(value));      }   }    return index; } 

and write method this:

public void write(listmultimap<object, object> index, outputstream out) throws ioexception {   properties properties = new properties();    (object key : index.keyset())   {     stringbuilder values = new stringbuilder();      (object value = index.get(key))     {       values.append(serailize(value)).append(",");     }       properties.setproperty(serailize(key), values.substring(0, values.length - 1));   }    properties.store(out, "saving"); } 

this example makes use of serialize , deserialize methods you'll need define according requirements signatures are:

public string serialize(object object) 

and

public object deserialize(string s)