20. Interfaces, including generic interfaces

Question 1

What is perhaps surprising about the way we say that a type argument of a generic class or interface or generic method, must implement a particular interface?

Answer 1

s

Question 2

What are the three components of a type? In what way does a class have these things?

Answer 2

s

Question 3

What typical trade-off is being shown when we compare this with the simplest way of searching a list?

Answer 3

s

Question 4

What is the instance method that implements a total order in Java typically called? What parameters does it take and what result does it produce?

Answer 4

s

Question 5

Which of the following, if any, are examples of multiple inheritance?

1. An instance of class A is a B and has a C.
2. An instance of class A is a B and also is a C, but B is not a C nor vice versa.
3. An instance of class A is a B which in turn is a C.
4. An instance of class A has a B and is a C

Answer 5

d

Question 6

What is the main difference between an interface and a class? What can interfaces not contain?

Answer 6

s

Question 7

Which of the three components of a type are provided by an interface, and which are provided by the classes that implement the interface?

Answer 7

s

Question 8

What simple errors might we make, and what can we write to protect us from them?

Answer 8

s

Question 9

If we do not supply type arguments for a generic interface when we use it, then what is it we are using?

Answer 9

s

Question 10

How many other interfaces can an interface extend? How many classes can an interface extend?

Answer 10

s

Question 11

How do we state that a class implements server interfaces?

Answer 11

s

Question 12

When might we want to have a generic method rather than a generic class? How do we call a generic method - where do we write the type argument(s)? Do we actually have to write them anyway?

Answer 12

s

Question 13

What do we mean by bound type parameter?

Answer 13

s

Question 14

What is the purpose of Arrays class?

Answer 14

s

Question 15

What must be true about the argument if it is an array of objects? (Arrays: sort())

Answer 15

s

Question 16

What is Arrays: copyOf() especially useful for? What is its type parameter?

Answer 16

s

Question 17

What instance method must be provided by any non-abstract class, that implements the Comparable interface?

Answer 17

s

Question 18

What should be the relationship between compareTo() and equals() methods?

Answer 18

s

Question 19

What notion of equivalence is implemented in Object?

Answer 19

s

Question 20

Exactly what parameterization of Comparable does String implement?

Answer 20

s