54 Javanotes 9.0, Quiz on Chapter 10

Quiz on Chapter 10

Question 1:

What is meant by generic
programming and what is the alternative?

Question 2:

Why can’t you make an object of type LinkedList<int>?
What should you do instead?

Question 3:

What is an iterator
and why are iterators necessary for generic programming?

Question 4:

Suppose that
integers is a variable of type Collection<Integer>.
Write a code segment that uses an iterator to compute the sum of all the integer values in
the collection. Write a second code segment that does the same thing using a
for-each loop.

Question 5:

Interfaces such as
List, Set, and Map
define abstract data types. Explain what this means.

Question 6:

What is the fundamental
property that distinguishes Sets from other types of
Collections?

Question 7:

What is the essential
difference in functionality between a TreeMap and a
HashMap?

Question 8:

Explain what is meant by a hash code.

Question 9:

Modify the following
Date class so that it implements the interface Comparable<Date>.
The ordering on objects of type Date should be the natural,
chronological ordering.

class Date {
   int month;  // Month number in range 1 to 12.
   int day;    // Day number in range 1 to 31.
   int year;   // Year number.
   Date(int m, int d, int y) { 
      month = m;
      day = d;
      year = y;
   }
}

Also, rewrite the resulting Date class as a record class.
(See Section 7.4.)

Question 10:

Suppose that
syllabus is a variable of type TreeMap<Date,String>,
where Date is the class from the preceding exercise.
Write a code segment that will write
out the value string for every key that is in the month of December, 2021.

Question 11:

Write a generic class Stack<T> that can be
used to represent stacks of objects of type T. The class
should include methods push(), pop(), and
isEmpty(). Inside the class, use an ArrayList
to hold the items on the stack.

Question 12:

Write a generic method, using a generic type parameter <T>,
that replaces every occurrence in an ArrayList<T> of a specified item
with a specified replacement item. The list and the two items are parameters to the method.
Both items are of type T.
Take into account the fact that the item that is being replaced might be null.
For a non-null item, use equals() to do the comparison.

Question 13:

Suppose that words is an array of Strings.
Explain what is done by the following code:

long n = Arrays.stream(words)
               .filter( w -> (w != null) )
               .map( w -> w.toLowerCase() )
               .distinct()
               .count();

Question 14:

Use the stream API to print all the even integers from 2 to 20.
Start with IntStream.range and apply a
filter operation.

Question 15:

Write a generic method countIf(c,t) with
type parameter <T>, where the first parameter,
c, is of type Collection<T>,
and the second parameter, p, is of type
Predicate<T>. The method should return
the number of items in the collection for which the predicate
is true. Give two versions, one using a loop and the other
using the stream API.

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