Adv Cs Spring '23 Test 2

Swing

100

Name four Swing components

JFrame, JPanel, JButton, JTextField, etc.

200

At most, how many child components can be shown in a JFrame that uses BorderLayout?

5

300

What is the Graphics object useful for?

It allows you to draw custom graphics on a component

400

What function is called whenever a Swing component re-renders?

paintComponent(Graphics g)

Streams, Comparators, and Optionals

100

What is an advantage of using Optional<Object> over a nullable Object?

Valid answers:

-Forces users to account for the null case (no surprise runtime exceptions)

-Makes code more concise (replace if statement with .orElse())

200

Give an example of an intermediate Stream operation and a terminal Stream operation

Intermediate: map, filter

Terminal: collect, findAny, sum

300

What is the difference between map() and flatMap()

map returns a single object, flatMap returns a stream that is "flattened" into the current stream 

400

You have created a FancyFurniture class, and you want to allow your furniture to be sorted by price (an instance variable of type double). You decide to have your class implement Comparable<FancyFurniture>. Write a compareTo function that will make your furniture's natural ordering be from cheapest to most expensive.

Something like:

public int compareTo(FancyFurniture o) {
        return this.price - o.getPrice();

}

2D Arrays / Recursion

100

Re-write the following function recursively:

public void countDown(int n) {
    while(n > 0) {
        System.out.println(n + "...");
        Thread.sleep(1000);
        n -= 1;
    }

}

Possible answer:

public void countDown(int n) {
        if(n == 0) {return;}
        System.out.println(n + "...");
        Thread.sleep(1000);
        countDown(n-1);
    }

200

What is the defining characteristic of tail recursion?

A few ways to think about it:

-The return value of every recursive call is the same

-The base case returns the final result

-The recursive call is at the very end of the function, after all the "work" is done

300

Write a function that takes in a 2D array, and converts it into a 1D array, going top-to-bottom and left-to-right.

public int[] flattenByColumn(int[][] arr) {}

[Answers will vary]

400

Write a function that takes in two arrays, and creates a 2D array where the top row is 0 and then arr1, the leftmost column is 0 and then arr2, and every other cell is the sum of the top of its column and leftmost of its row

public int[][] sum(int[] arr1, int[] arr2) {}

[Answers will vary]