AP CSA 1.12 Exercise 1: Two Books, One Class

Unit 1: Using Objects and Methods · Lesson 1.12 · Exercise 1

Two Books, One Class

Objects: Instances of Classes. Write real Java, run it, and submit it to be graded against hidden test cases.

Back to the Lesson 1.12 page All Unit 1 lessons

Why this one is worth doing

One class, two instances, two separate sets of values. The class is the blueprint and it holds no data of its own, which is the whole idea this lesson is built on.

What to write

The Book class is written for you. Do not change it.
Read a title, a page count, and a second title and page count.
Create two Book objects from those values.
Print each book description on its own line by calling describe() on each object.
Print the total number of pages across both books.

Your program reads

A word, an integer, a word and an integer, each on its own line.

Your program prints

Three lines: the first description, the second description, and the total page count.

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

Dune
412
Hamlet
160

Example 1 output

Dune (412p)
Hamlet (160p)
572

Example 2 input

Emma
1
Odyssey
2

Example 2 output

Emma (1p)
Odyssey (2p)
3

Your answer

Main.java

import java.util.Scanner;

class Book {
  private String title;
  private int pages;

  public Book(String title, int pages) {
    this.title = title;
    this.pages = pages;
  }

  public int getPages() { return pages; }

  public String describe() { return title + " (" + pages + "p)"; }
}

public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    String t1 = input.next();
    int p1 = input.nextInt();
    String t2 = input.next();
    int p2 = input.nextInt();

    // Create two Book objects and use them.
  }
}

Input for the Run button

Run sends whatever is in the input box below. Submitting runs your program against every test case, including hidden ones with different input.

Stuck?

Hint 1

new Book(t1, p1) makes one instance. Calling it twice makes two, and they do not share their title or page count.

Hint 2

describe() is called on an object, not on the class: first.describe(), never Book.describe().

Hint 3

The Book class already stores the values. You do not need to print the title yourself, and you must not edit the class.

Where to go next

Rework the Lesson 1.12 page Pick another Unit 1 lesson

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