TaskStorage.java

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;

public class TaskStorage {
	private static final String FILE_NAME = "tasks.json";

	// create file if it doesn't exist
	public static void createFile() {
		File file = new File(FILE_NAME);
		if (!file.exists()) {
			try (FileWriter fw = new FileWriter(file)) {
				fw.write("[]"); // empty list
			} catch (IOException e) {
				System.out.println("Error for creating the file " + e.getMessage());
			}
		}
	}

	// load tasks from file
	public static List<Task> loadTasks() {
		List<Task> tasks = new ArrayList<>();
		try {
			String content = Files.readString(Path.of(FILE_NAME)).trim();
			if (!content.startsWith("[") || !content.endsWith("]")) return tasks;

			content = content.substring(1, content.length() - 1).trim(); // eliminate [ and ]
			if (content.isEmpty()) return tasks;

			String[] jsonTasks = content.split("},\\s*\\{");

			for (int i = 0; i < jsonTasks.length; i++) {
				String json = jsonTasks[i];
				if (!json.startsWith("{")) json = "{" + json;
				if (!json.endsWith("}")) json = json + "}";

				tasks.add(Task.fromJSON(json));
			}
		} catch (IOException e) {
			System.out.println("Error at reading the file: " + e.getMessage());
		}

		return tasks;
	}

	// save tasks in file
	public static void saveTasks(List<Task> tasks) {
		try (FileWriter writer = new FileWriter(FILE_NAME)) {
			writer.write("[\n");
			for (int i = 0; i < tasks.size(); i++) {
				writer.write(" " + tasks.get(i).toJSON());
				if (i != tasks.size() - 1) writer.write(",");
				writer.write("\n");
			}
			writer.write("]");
		} catch (IOException e) {
			System.out.println("Error at saving the file: " + e.getMessage());
		}
	}
}