Why methods are needed in Java - See It in Action

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Why Methods Are Needed

📖 Scenario: Imagine you are organizing a small library. You need to keep track of books and perform actions like adding new books and showing all books. Doing these tasks repeatedly in the main program can get messy and confusing.

🎯 Goal: You will create a simple Java program that uses methods to organize tasks like adding books and displaying the list. This will show why methods are helpful to keep code clean and reusable.

📋 What You'll Learn

Create a method to add a book to the list

Create a method to display all books

Use methods in the main program to manage books

💡 Why This Matters

🌍 Real World

In real software, methods help break down big tasks into smaller steps, making code easier to manage and reuse.

💼 Career

Understanding methods is essential for any programming job because they are the building blocks of clean, efficient code.

1

Create the initial book list

Create an ArrayList of String called books and add these exact books: "Java Basics", "Data Structures", "Algorithms".

Java

import java.util.ArrayList;

// Create the books list and add initial books
// Your code here

💡 Need a hint?

Use ArrayList<String> and the add method to add books.

2

Create a method to add a book

Add a static method called addBook that takes an ArrayList<String> books and a String book as parameters and adds the book to the list.

Java

import java.util.ArrayList;

public class Library {
    public static void main(String[] args) {
        ArrayList books = new ArrayList();
        books.add("Java Basics");
        books.add("Data Structures");
        books.add("Algorithms");
    }

    // Create addBook method below
    // Your code here
}

💡 Need a hint?

Define a method with public static void addBook(ArrayList books, String book) and use books.add(book); inside.

3

Create a method to display all books

Add a static method called displayBooks that takes an ArrayList<String> books and prints each book on a new line using a for loop.

Java

import java.util.ArrayList;

public class Library {
    public static void main(String[] args) {
        ArrayList books = new ArrayList();
        books.add("Java Basics");
        books.add("Data Structures");
        books.add("Algorithms");
    }

    public static void addBook(ArrayList books, String book) {
        books.add(book);
    }

    // Create displayBooks method below
    // Your code here
}

💡 Need a hint?

Use a for-each loop to print each book inside the method.

4

Use methods to add and display books

In the main method, use addBook(books, "Design Patterns") to add a new book, then call displayBooks(books) to print all books.

Java

import java.util.ArrayList;

public class Library {
    public static void main(String[] args) {
        ArrayList books = new ArrayList();
        books.add("Java Basics");
        books.add("Data Structures");
        books.add("Algorithms");

        // Use addBook to add "Design Patterns"
        // Use displayBooks to print all books
        // Your code here
    }

    public static void addBook(ArrayList books, String book) {
        books.add(book);
    }

    public static void displayBooks(ArrayList books) {
        for (String book : books) {
            System.out.println(book);
        }
    }
}

💡 Need a hint?

Call addBook(books, "Design Patterns") and then displayBooks(books) inside main.