Use cases in Java - Mini Project: Build & Apply

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Use Cases in Java

📖 Scenario: You are building a simple program to manage a library system. The system needs to keep track of books and their availability.

🎯 Goal: Create a Java program that stores book titles and their availability status, then prints out the available books.

📋 What You'll Learn

Create a dictionary-like data structure to store book titles and availability

Add a configuration variable to represent the availability status to filter

Use a loop to find all books that are available

Print the list of available books

💡 Why This Matters

🌍 Real World

Managing collections of items with their properties is common in library systems, inventory management, and many business applications.

💼 Career

Understanding how to use maps and loops to filter data is a fundamental skill for software developers working with data structures.

1

Create the initial data structure

Create a HashMap<String, Boolean> called books with these exact entries: "The Hobbit" as true, "1984" as false, "Pride and Prejudice" as true.

Java

// Your code here

💡 Need a hint?

Use HashMap<String, Boolean> and put method to add entries.

2

Add availability filter variable

Add a boolean variable called availableStatus and set it to true to represent the availability status to filter.

Java

import java.util.HashMap;

public class Library {
    public static void main(String[] args) {
        HashMap books = new HashMap();
        books.put("The Hobbit", true);
        books.put("1984", false);
        books.put("Pride and Prejudice", true);
        // Your code here
    }
}

💡 Need a hint?

Declare a boolean variable named availableStatus and assign true.

3

Find available books using a loop

Use a for loop with variables title and isAvailable to iterate over books.entrySet(). Inside the loop, check if isAvailable equals availableStatus. If yes, add title to a new ArrayList<String> called availableBooks.

Java

import java.util.HashMap;
import java.util.ArrayList;

public class Library {
    public static void main(String[] args) {
        HashMap books = new HashMap();
        books.put("The Hobbit", true);
        books.put("1984", false);
        books.put("Pride and Prejudice", true);
        boolean availableStatus = true;
        ArrayList availableBooks = new ArrayList();
        // Your code here
    }
}

💡 Need a hint?

Use books.entrySet() to loop through the map entries.

4

Print the available books

Print the availableBooks list using System.out.println.

Java

import java.util.HashMap;
import java.util.ArrayList;
import java.util.Map;

public class Library {
    public static void main(String[] args) {
        HashMap books = new HashMap();
        books.put("The Hobbit", true);
        books.put("1984", false);
        books.put("Pride and Prejudice", true);
        boolean availableStatus = true;
        ArrayList availableBooks = new ArrayList();
        for (Map.Entry entry : books.entrySet()) {
            String title = entry.getKey();
            Boolean isAvailable = entry.getValue();
            if (isAvailable == availableStatus) {
                availableBooks.add(title);
            }
        }
        // Your code here
    }
}

💡 Need a hint?

Use System.out.println(availableBooks); to print the list.