TaskManager.java

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

public class TaskManager {
    private static TaskManager instance;
    private List<Task> taskList = new ArrayList<>();

    private TaskManager(){
    }

    public static TaskManager getInstance(){
        if(instance == null){
            instance = new TaskManager();
        }
        return instance;
    }

    public void addTask(Task task){
        taskList.add(task);
        System.out.println("Task added successfully! \n");
    }

    // view all tasks 
    public void viewAllTasks(){
        if(taskList.isEmpty()){
            System.out.println("No tasks found. \n");
            return;
        }
        for(Task task : taskList){
            String status = task.getStatus() ? "done":"Pending";
            System.out.println(task.getTitle()+"--"+task.getDescription()+". Status: "+status);
        }
        System.out.println();
    }

    // view tasks by tag
    public void viewTasksByTag(String tag){
        boolean found = false;
        for (Task task: taskList) {
        String status = task.getStatus() ? "done":"Pending";
            if (task.getTag().equalsIgnoreCase(tag)) {
                System.out.println(task.getTitle()+"--"+task.getDescription()+". Status: "+status);
                found = true;
            }    
        }
        if(!found){
            System.out.println("Task not found with this tag: "+tag);
        }
    }

    // Mark As Done
    public void markAsDone(String title){
        for(Task task: taskList){
            if(task.getTitle().equalsIgnoreCase(title)){
                task.setStatus(true);
                System.out.println("This task marked as Done.");
                return;
            }
        }
        System.out.println("Task not found.\n");
    }

    // Delete task
    public void deleteTask(String title){
        Iterator<Task> iterator = taskList.iterator();
        while (iterator.hasNext()) {
            Task task = iterator.next();
            if(task.getTitle().equalsIgnoreCase(title)){
                iterator.remove();
                System.out.println("Task deleted successfully.");
                return;
            }
        }
        System.out.println("Task not found.\n");
    }
}