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Assignment 5: Interfaces Solved


·Source code: Coffee.java; CoffeeTest.java; PersonTest.java.




Exercise 1


Java defines a  Comparable interface (  java.lang.Comparable ); this interface is a parameterized interface. We will discuss parameterized classes and interfaces in detail later in the course. For now, you do not need to know too much about parameterization -- just use it.


Read the code in Coffee.java. You are required to complete the class definition to allow collections of coffees to be sorted by the strength.

Find the code from CoffeeTest.java. What imports are required to allow it to compile? And how would I rewrite this class to utilize JUnit? Create a JUnit project as submission.


Exercise 2

Consider the code below. It describes 5 types either classes or interfaces.


U u; G g; B b; Z z; X x;



The following assignments are all legal and compile:


u = z; x = b; g = u; x = u;


However, the following assignments are all illegal and cause compilation errors:



1 of 5    2018-12-22, 9:20 p.m.

Assignment    https://eclass.srv.ualberta.ca/mod/assign/view.php?id=3237747




u = b; x = g; b = u; z = u; g = x;


What can you state about the types and their relationships (to each other)? Provide at least one possible answer.


Exercise 3

The collections library has a class  TreeSet (  java.util.TreeSet ). It is another parameterised class which is an example of a sorted set. That is, elements in this set are kept in order. Construct classes Person and  PersonCompator to make the  runTest in PersonTest.java successfully complete. This method checks if  Person  objects are correctly ordered by their ages (age is the only attribute of  Person ). PersonComparator is required to implement

interface  Comparator  (  java.util.Comparator ).  Comparator is another parameterised interface -- parameterization is common in Java.

What imports are required to allow it to compile? And how would I rewrite this class to utilize JUnit?

Create a JUnit project as submission.

Coffee.java 


CoffeeTest.java 


PersonTest.java 


 

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