How to store hashmap so that it can be retained it value after a device reboot?

serialize your hashmap object before restarting and deserialize it after restart…

here is sample code for serialization..

public void serializeMap(HashMap<String,String> hm) {
    try {
        FileOutputStream fStream = openFileOutput(namefile.bin, Context.MODE_PRIVATE) ;
        ObjectOutputStream oStream = new ObjectOutputStream(fStream);

        oStream.writeObject(hm);        
        oStream.flush();
        oStream.close();

        Log.v("Serialization success", "Success");
    } catch (Exception e) {
        Log.v("IO Exception", e.getMessage());
    }
}   

you can similarly read it by deserializing it….
Thanks….