Describe, without excessive handwaving, two common uses for interfaces.

Given the SupplyDepot, Transport, and CapableOfBeingRefuelled classes/interfaces described earlier in this chapter, add a main routine to Airplane. Then add fields, parameters, and code to SupplyDepot and elsewhere so that a CapableOfBeingRefuelled can tell the service routine how much fuel it takes. Make sure that amount of fuel is decremented at the Depot, and incremented in the object that implements CapableOfBeingRefuelled.

Look at the Cloneable interface in javadoc. Take any class that you have written and make it cloneable by making it implement the Cloneable interface.

Override Object.clone() to do a shallow copy for your class, and also keep count of the number of objects of your class that have been created. Don't forget to count those created via a constructor, too.

Write some code to clone an object of your class. Change your version of clone() to do a deep copy for your class. Run the clone program again, and make it print out enough information that you can tell the difference between a shallow clone and a deep clone.