Kiril Mishevski

1import java.util.ArrayList;
2import java.util.Collections;
3import java.util.List;
4 
5/**
6 * A class to manage a collection of tasks, providing functionality to add, remove,
7 * and retrieve tasks. This class ensures thread-safe access to the task list and
8 * includes input validation for robust task management.
9 *
10 * @author Kiril Mishevski
11 * @version 3.2.4
12 */
13public class TaskManager {
14    private final List<String> tasks;
15 
16    /**
17     * Constructs a new TaskManager with an empty task list.
18     */
19    public TaskManager() {
20        tasks = new ArrayList<>();
21    }
22 
23    /**
24     * Adds a task to the task list if it is valid (non-null and non-empty).
25     *
26     * @param task the task description to add
27     * @throws IllegalArgumentException if the task is null or empty
28     */
29    public void addTask(String task) {
30        if (task == null || task.trim().isEmpty()) {
31            throw new IllegalArgumentException("Task cannot be null or empty");
32        }
33        synchronized (tasks) {
34            tasks.add(task.trim());
35        }
36    }
37 
38    /**
39     * Removes a task from the list at the specified index.
40     *
41     * @param index the index of the task to remove
42     * @return true if the task was removed successfully, false if the index is invalid
43     * @throws IndexOutOfBoundsException if the index is out of range
44     */
45    public boolean removeTask(int index) {
46        synchronized (tasks) {
47            if (index < 0 || index >= tasks.size()) {
48                throw new IndexOutOfBoundsException("Invalid index: " + index);
49            }
50            tasks.remove(index);
51            return true;
52        }
53    }
54 
55    /**
56     * Retrieves an unmodifiable view of the current task list.
57     *
58     * @return an unmodifiable list of tasks
59     */
60    public List<String> getTasks() {
61        synchronized (tasks) {
62            return Collections.unmodifiableList(new ArrayList<>(tasks));
63        }
64    }
65 
66    /**
67     * Returns the number of tasks in the task list.
68     *
69     * @return the number of tasks
70     */
71    public int getTaskCount() {
72        synchronized (tasks) {
73            return tasks.size();
74        }
75    }
76 
77    /**
78     * Demonstrates the usage of the TaskManager class with example operations.
79     *
80     * @param args command-line arguments (not used)
81     */
82    public static void main(String[] args) {
83        TaskManager manager = new TaskManager();
84        try {
85            manager.addTask("Complete portfolio project");
86            manager.addTask("Update resume");
87            System.out.println("Tasks: " + manager.getTasks());
88            System.out.println("Task count: " + manager.getTaskCount());
89            manager.removeTask(0);
90            System.out.println("Tasks after removal: " + manager.getTasks());
91        } catch (IllegalArgumentException | IndexOutOfBoundsException e) {
92            System.err.println("Error: " + e.getMessage());
93        }
94    }
95}