AP CSA 3.2 Exercise 1: Scoreboard Interface

Unit 3: Class Creation · Lesson 3.2 · Exercise 1

Scoreboard Interface

Impact of Program Design. Write real Java, run it, and submit it to be graded against hidden test cases.

Back to the Lesson 3.2 page All Unit 3 lessons

Why this one is worth doing

What a method returns is a design decision with consequences. leader returns a NAME and margin returns a NUMBER, and a caller that only had the raw scores would have to work both out for itself every time.

What to write

Write a class named Scoreboard that tracks two team names and their scores. Both scores start at zero.
scoreHome and scoreAway add points to the right team.
getHomeScore and getAwayScore return the current scores.
leader returns the name of the team that is ahead, or the exact word TIE when the scores are equal.
margin returns how far ahead the leader is, which is never negative.

Your program reads

The grader supplies the input. Your class does not read anything.

Your program prints

Your class prints nothing. The grader prints what your methods return.

The class the grader will call

Your answer must declare exactly these, spelled exactly like this. The grader creates the object and calls the methods itself, so a method under a different name is a method it cannot find.

class Scoreboard
Scoreboard(String homeName, String awayName)
void scoreHome(int points)
void scoreAway(int points)
int getHomeScore()
int getAwayScore()
String leader()
int margin()

Do not write a class named Main and do not write a main method. The grader supplies its own.

Worked examples

These are the cases you can see. There are more you cannot, and they use different values, so an answer that prints these numbers as constants will fail.

Example 1 input

Lions Bears
3
1 7
2 3
1 3

Example 1 output

TIE
10
3
Lions
7

Example 2 input

Reds Blues
0

Example 2 output

TIE
0
0
TIE
0

Your answer

Main.java

class Scoreboard {
  // Instance variables for the two names and the two scores.

  public Scoreboard(String homeName, String awayName) {

  }

  public void scoreHome(int points) {

  }

  public void scoreAway(int points) {

  }

  public int getHomeScore() {
    return 0;
  }

  public int getAwayScore() {
    return 0;
  }

  public String leader() {
    return "";
  }

  public int margin() {
    return 0;
  }
}

Input for the Run button

Run uses the sample main shown below, which is not the one that grades you. Submitting runs your class against the real cases, including hidden ones.

The sample main the Run button uses

public class Main {
  public static void main(String[] args) {
    Scoreboard board = new Scoreboard("Lions", "Bears");
    board.scoreHome(7);
    board.scoreAway(3);
    System.out.println(board.leader());
    System.out.println(board.margin());
  }
}

Stuck?

Hint 1

A brand new Scoreboard has both scores at zero, so leader() has to answer TIE before anybody has scored.

Hint 2

margin is never negative. Math.abs on the difference handles both directions in one expression.

Hint 3

Return the stored name, not a copy you typed out. The team names come from whoever built the object.

Where to go next

Rework the Lesson 3.2 page Pick another Unit 3 lesson

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