Spring Test 2 Review

Streams & Reductions

100

For each of these stream functions, indicate whether it is terminal or intermediary:

1. map()

2. findAny()

3. limit()

4. distinct()

1. map() => intermediate

2. findAny() => terminal

3. limit() => intermediate

4. distinct() => intermediate

200

What is the value of "result" after this code runs:

List<String> words = List.of("a", "b" "aa", "bb", "abc");

long result = words.stream()

    .map(w -> w.length())

    .distinct()

    .count();

3

300

[Comeback Question]
A Planet class includes getters and setters for numMoons (int) and name (String).

Using streams, write some code that that takes a list of Planets and creates a list of the names of the planets that have at least 2 moons.

planets.stream()

    .filter(p -> p.getNumMoons() >= 2)

    .map(p -> p.getName())

    .collect(Collectors.toList());

400

Using streams, write code that takes a list of Strings and produces a String containing the concatenated first letters of each String.

e.g. words.stream()...

One possible solution:

words.stream()

    .reduce("", (a, w) -> a + w.charAt(0));

Java Swing

100

What does GUI stand for?

Graphical User Interface

200

What are the 5 regions supported by BorderLayout?

NORTH, SOUTH, EAST, WEST, CENTER

300

In programs like Paint where you are drawing custom shapes, what class do you likely want to extend, and what function do you need to implement?

JPanel

paintComponent(Graphics g)

^ you get credit even if you didn't include Graphics g

400

Write a class for a custom Swing component that contains two side-by-side text fields. The constructor should take in the contents of the two text fields.

You may want to reference some of the following classes:

JFrame, JPanel, JLabel, JButton, JTextField

[Code may vary]

Other

100

[Comeback Question]

Using recursion, write a function that counts the number of times the letter "e" appears in a String

public static void countE(String s) {

    if (s.isEmpty()) { return 0; }

    int firstCount = s.charAt(0) == "e" ? 1 : 0;

    return firstCount + countE(s.substring(1));

}

200

[Blue Shell]

You have the following code, which calls an unknown function findItem():

Optional<String> result = findItem();

Write some code that prints out "No item was found" if result is empty, or the result if one was returned.

System.out.println(result.orElse("No item was found));

300

[Comeback Question]

int x = 6; int y = 7;

int z = (x < y && y < 8) ? -1 : 1;

What is z?

-1

400

Collection<String> list = List.of("mercury", "valkyrie", "sky");

XXXXX result = list.stream().sorted(

    (a, b) -> a.charAt(1) - b.charAt(1))

    .findFirst().get();

 What type and value does result have?

String, "Valkyrie"