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In this section, we will walk through the process of developing a simple console application in Java. This will help you understand how to apply the concepts you've learned so far in a practical, real-world scenario.

Objectives

Understand the structure of a console application.
Learn how to handle user input and output.
Implement basic functionality using control flow and data structures.
Practice debugging and testing your application.

Steps to Develop a Console Application

Define the Problem

Before writing any code, it's essential to understand what the application is supposed to do. Let's create a simple "To-Do List" application that allows users to:

Add tasks.
View all tasks.
Mark tasks as completed.
Remove tasks.

Plan the Application Structure

Break down the application into smaller, manageable parts:

Task Class: Represents a single task.
ToDoList Class: Manages a list of tasks.
Main Class: Handles user interaction and controls the flow of the application.

Implement the Task Class

The Task class will have attributes for the task description and its completion status.

public class Task {
    private String description;
    private boolean isCompleted;

    public Task(String description) {
        this.description = description;
        this.isCompleted = false;
    }

    public String getDescription() {
        return description;
    }

    public boolean isCompleted() {
        return isCompleted;
    }

    public void markAsCompleted() {
        this.isCompleted = true;
    }

    @Override
    public String toString() {
        return (isCompleted ? "[X] " : "[ ] ") + description;
    }
}

Implement the ToDoList Class

The ToDoList class will manage a list of Task objects.

import java.util.ArrayList;
import java.util.List;

public class ToDoList {
    private List<Task> tasks;

    public ToDoList() {
        tasks = new ArrayList<>();
    }

    public void addTask(String description) {
        tasks.add(new Task(description));
    }

    public void removeTask(int index) {
        if (index >= 0 && index < tasks.size()) {
            tasks.remove(index);
        } else {
            System.out.println("Invalid task number.");
        }
    }

    public void markTaskAsCompleted(int index) {
        if (index >= 0 && index < tasks.size()) {
            tasks.get(index).markAsCompleted();
        } else {
            System.out.println("Invalid task number.");
        }
    }

    public void viewTasks() {
        if (tasks.isEmpty()) {
            System.out.println("No tasks available.");
        } else {
            for (int i = 0; i < tasks.size(); i++) {
                System.out.println((i + 1) + ". " + tasks.get(i));
            }
        }
    }
}

Implement the Main Class

The Main class will handle user input and control the flow of the application.

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        ToDoList toDoList = new ToDoList();
        Scanner scanner = new Scanner(System.in);
        boolean exit = false;

        while (!exit) {
            System.out.println("\nTo-Do List Application");
            System.out.println("1. Add Task");
            System.out.println("2. View Tasks");
            System.out.println("3. Mark Task as Completed");
            System.out.println("4. Remove Task");
            System.out.println("5. Exit");
            System.out.print("Choose an option: ");
            int choice = scanner.nextInt();
            scanner.nextLine();  // Consume newline

            switch (choice) {
                case 1:
                    System.out.print("Enter task description: ");
                    String description = scanner.nextLine();
                    toDoList.addTask(description);
                    break;
                case 2:
                    toDoList.viewTasks();
                    break;
                case 3:
                    System.out.print("Enter task number to mark as completed: ");
                    int taskNumberToComplete = scanner.nextInt();
                    toDoList.markTaskAsCompleted(taskNumberToComplete - 1);
                    break;
                case 4:
                    System.out.print("Enter task number to remove: ");
                    int taskNumberToRemove = scanner.nextInt();
                    toDoList.removeTask(taskNumberToRemove - 1);
                    break;
                case 5:
                    exit = true;
                    break;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        }

        scanner.close();
    }
}

Testing and Debugging

Run the application and test each functionality:

Add a few tasks.
View the list of tasks.
Mark tasks as completed.
Remove tasks.
Ensure the application handles invalid inputs gracefully.

Common Mistakes and Tips

Input Handling: Always validate user input to avoid exceptions.
Index Management: Remember that list indices start at 0, but user-friendly numbering often starts at 1.
Code Organization: Keep your code organized and modular to make it easier to maintain and extend.

Conclusion

In this section, you learned how to develop a simple console application in Java. You applied various concepts such as classes, objects, methods, and control flow to build a functional "To-Do List" application. This exercise helps reinforce your understanding of Java programming and prepares you for more complex projects.

Next, you will learn about developing web applications, which will introduce you to new concepts and technologies for building more sophisticated and interactive applications.

Developing a Console Application

Objectives

Steps to Develop a Console Application

Define the Problem

Plan the Application Structure

Implement the Task Class

Implement the ToDoList Class

Implement the Main Class

Testing and Debugging

Common Mistakes and Tips

Conclusion

Java Programming Course

Module 1: Introduction to Java

Module 2: Control Flow

Module 3: Object-Oriented Programming

Module 4: Advanced Object-Oriented Programming

Module 5: Data Structures and Collections

Module 6: Exception Handling

Module 7: File I/O

Module 8: Multithreading and Concurrency

Module 9: Networking

Module 10: Advanced Topics

Module 11: Java Frameworks and Libraries

Module 12: Building Real-World Applications