Question

In my current project, I am trying to make a uniform interfaces of all sensor driver.

For instance, Temperature sensor has a temperature sensor driver to get data from
it.

Now, my problem is each sensor response with its own data Object. I have written following example of Temperature Sensor. How can I make sensor driver interface uniform, so programmer should only know SensorResonse (not TempSensorResponse).

public class TempSensor implements Sensor {


    /**
     * Returns a SensorInfo object that describes this sensor.
     */
    @Override
    public TempSensorInfo getSensorInfo() {
        // TODO Auto-generated method stub
        return null;
    }

    /**
     * Asks the sensor for a (possibly old) datapoint. Synchronous: returns
     * immediately, even if that means returning an old value.
     */
    @Override
    public TempResponse getData() {
        // TODO Auto-generated method stub
        return null;
    }

    /**
     * Asks the sensor for a new datapoint. Asynchronous.
     *
     * @param handler A Handler object to be executed when the sensor has a
     * new value. If this Sensor is event-based, this method starts listening
     * for data, and calls the handler whenever new events are detected.
     */
    @Override
    public void getData(SensorListener handler) {
        // TODO Auto-generated method stub

    }

}

/**
* A SensorResponse is the response that a sensor passes to its callee whenever
* it is asked for some data. It carries both the sensor data itself as it does
* some metadata about it, such as the SensorInfo of the sensor that produced
* this response.
*/

public class TempResponse extends SensorResponse {


    public TempResponse(TempSensorInfo sensorInfo, TempSensorData payload) {
        super(sensorInfo, payload);
        // TODO Auto-generated constructor stub
    }

}

Answer 1

Use generics:

Make an interface/base classes.

public interface ISensor 
    <I extends ISensor.SensorInfo, 
     R extends ISensor.SensorResponse, 
     L extends ISensor.SensorListener> 
{

    /**
    * Returns a SensorInfo object that describes this sensor.
    */
    public I getSensorInfo();

    /**
    * Asks the sensor for a (possibly old) datapoint. Synchronous: returns
    * immediately, even if that means returning an old value.
    */
    public R getData();

    /**
    * Asks the sensor for a new datapoint. Asynchronous.
    * 
    * @param handler
    *            A Handler object to be executed when the sensor has a new
    *            value. If this Sensor is event-based, this method starts
    *            listening for data, and calls the handler whenever new events
    *            are detected.
    */
    public void getData(L handler);

    public static class SensorInfo { }
    public static class SensorResponse { }
    public static class SensorListener { }
}

Make your sensors implement/extend the interface/classes:

public class TemperatorSensor 
    implements ISensor 
        <TemperatorSensor.TemperatorInfo, 
         TemperatorSensor.TemperatorResponse, 
         TemperatorSensor.TemperatorListener> 
{

    @Override
    public TemperatorInfo getSensorInfo() {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public TemperatorResponse getData() {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void getData(TemperatorListener handler) {
        // TODO Auto-generated method stub
    }

    public static final class TemperatorInfo extends ISensor.SensorInfo { }
    public static final class TemperatorResponse extends ISensor.SensorResponse { }
    public static final class TemperatorListener extends ISensor.SensorListener { }
}

Without using Generics:

Base interface/classes

public interface ISensor {

    /**
     * Returns a SensorInfo object that describes this sensor.
     */
    public ISensor.SensorInfo getSensorInfo();

    /**
     * Asks the sensor for a (possibly old) datapoint. Synchronous: returns
     * immediately, even if that means returning an old value.
     */
    public ISensor.SensorResponse getData();

    /**
     * Asks the sensor for a new datapoint. Asynchronous.
     * 
     * @param handler
     *            A Handler object to be executed when the sensor has a new
     *            value. If this Sensor is event-based, this method starts
     *            listening for data, and calls the handler whenever new events
     *            are detected.
     */
    public void getData(ISensor.SensorListener handler);

    public static class SensorInfo { }
    public static class SensorResponse { }
    public static class SensorListener { }
}

Extended interface/classes

public class TemperatorSensor implements ISensor {

    @Override
    public SensorInfo getSensorInfo() {
        // TODO Auto-generated method stub
        return new TemperatorInfo();
    }

    @Override
    public SensorResponse getData() {
        // TODO Auto-generated method stub
        return new TemperatorResponse();
    }

    @Override
    public void getData(SensorListener handler) {
        if (handler instanceof TemperatorListener) {
            // TODO Auto-generated method stub
        }
    }

    public static final class TemperatorInfo extends ISensor.SensorInfo { }
    public static final class TemperatorResponse extends ISensor.SensorResponse { }
    public static final class TemperatorListener extends ISensor.SensorListener { }
}