Initialization help ASAP plz

Hi, i've initialized a config file which is a Configuration file created via
Configuration config = new Configuration;
that has the call .read(); in it which reads a data file that has configurations ex. (file-input-type a)
which has the method .getInputMethod() which grabs an interface of the input type a and then initializes it like so
          try {
          config.getInputMethod ().initialize (config, sourceArgs);
          config.getBallotFormat ().initialize (config);
          config.getVotingSystem ().initialize (config);
my question is, if the config is only initialized through the interface how can i invoke the class method of the class that the interface implements? furthermore, can someone explain to me more about interfaces
please help, i've been stuck for two days and i wish to move on, my project's due in 2 days :(


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