Exercises Java with Examples-
Practice Exercises Java 4,5 5 302940

ArrayList - Text file reader - Practice Exercises Java


Lesson 11:

Dynamic memory management


Exercise 11.8:

ArrayList - Text file reader


Objetive:

Deliver here your basic text file reader.

This text file reader always shows 21 lines of the text file, and the user could use up key to show the previous line, down key to show the next line, and ESC key to exit.

Hints:
The text file reader should have 3 methods:
- ReadFile (Read the text file and store it in memory)
- ShowMenu (Clear the console and prepare the top line and the bottom line [raw 23] of the console, changing colours using Console.BackgroundColor, Console.ForegroundColor, ConsoleColor and Console.SetCursorPosition(column, raw). Once the menu is prepared, remember to set the cursor in the second raw).
- ShowFrom (write 21 lines, considering the position of the first line to write)
The logic of the main program should be like: ShowMenu, ShowFrom, ReadKey, ShowMenu, ShowFrom, ReadKey....


Source Code:


import java.util.*;
public class Main
{
	private static ArrayList lista = new ArrayList();
	private static boolean fin;
	private static int lineaDesde = 0, lineaHasta = 21;

	static void main(String[] args)
	{
		System.out.print("Introduce nombre archivo: ");
		String nombreArchivo = new Scanner(System.in).nextLine();

		LeerFichero(nombreArchivo);

		do
		{
			MostrarMenu();
			EscribirLineas(lineaDesde, lineaHasta);
			LeerTecla();
		} while (!fin);

	}
	private static void LeerTecla()
	{
		ConsoleKeyInfo cki = new ConsoleKeyInfo();
		cki = Console.ReadKey();

		if (cki.Key == ConsoleKey.Escape)
		{
			fin = true;
		}
		else if (cki.Key == ConsoleKey.UpArrow)
		{
			if (lineaDesde > 0)
			{
				lineaDesde--;
				lineaHasta--;
			}
		}
		else if (cki.Key == ConsoleKey.DownArrow)
		{
			if (lineaHasta < lista.size())
			{
				lineaDesde++;
				lineaHasta++;
			}
		}
		else if (cki.Key == ConsoleKey.PageUp)
		{
			if ((lineaHasta + 21) < lista.size())
			{
				lineaDesde += 21;
				lineaHasta += 21;
			}
			else
			{
				lineaDesde += lista.size() - lineaHasta;
				lineaHasta += lista.size() - lineaHasta;
			}
		}
		else if (cki.Key == ConsoleKey.PageDown)
		{
			if ((lineaDesde - 21) > 0)
			{
				lineaDesde -= 21;
				lineaHasta -= 21;
			}
			else
			{
				lineaHasta = lineaDesde + (21 - lineaDesde);
				lineaDesde = 0;
			}
		}
	}

	private static void EscribirLineas(int desde, int hasta)
	{
		for (int i = desde; i < hasta; i++)
		{
			System.out.println(lista.get(i));
		}
	}

	private static void MostrarMenu()
	{
		Console.Clear();
		Console.BackgroundColor = ConsoleColor.Cyan;
		Console.ForegroundColor = ConsoleColor.Black;
		System.out.println("    ==> Lector .txt --- Version 1.0");

		Console.SetCursorPosition(0, 23);
		Console.BackgroundColor = ConsoleColor.Cyan;
		Console.ForegroundColor = ConsoleColor.Black;
		System.out.println("Pulse ESC para salir, fecha arriba y abajo para mover");

		Console.SetCursorPosition(0, 1);
		Console.BackgroundColor = ConsoleColor.Black;
		Console.ForegroundColor = ConsoleColor.White;
	}

	private static void LeerFichero(String nombreArchivo)
	{
		if (!(new java.io.File(nombreArchivo)).isFile())
		{
			System.out.println("El fichero de texto no existe");
		}
		else
		{
			try
			{
				java.io.FileReader archivoTexto = new java.io.FileReader(nombreArchivo);
			java.io.BufferedReader archivoTextoBufferedReader = new java.io.BufferedReader(archivoTexto);
				String line;

				do
				{
					line = archivoTextoBufferedReader.readLine();
					if (line != null)
					{
						lista.add(line);
					}
				} while (line != null);

				archivoTexto.close();
			}
			catch (RuntimeException e)
			{
				System.out.println("Error, " + e.getMessage());
			}
		}
	}
}
Exercisey 11.8

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