How to achieve multiple inheritance in java

Question

I am designing Traveller App. For which I need to design 'Traveller' class and with its instance I should be able to access properties of different types of Travel modes.

class Traveller {

// common properties.
}

class RoadTravel {
 // properties specific to class
}

class WaterTravel {
// properties specific to class
}

class RailTravel {
// properties specific to class
}

from the above code , I just want to create instance of 'Traveller' class and should be able to access the properties of all other classes (RoadTravel,WaterTravel,RailTravel).

I dont want to create any dependency on my sub classes and also my instance variables should not be final.

Please suggest good way of implementation so that it should be easy to add any new type of Travel mode in future.

Answer 1

In Java you cannot have a class which extends (inherits) from multiple classes. (You might want to look into the Deadly Diamond of Death Problem.

In your case, what you could have would be a Travel interface which defines the behaviour each of your travel types need to expose, such as cost(int duration), getName(). etc/

Your logic would then use the Travel interface to do it's logic. The travel type dependent logic would be stored in the seperate classes which make use of the Travel interface. Your main logic would then delegate travel specific logic to these classes which are passed to it at run time.

You will need to take a look at the Strategy Design Pattern to see how you can implement this.