Java shortcut files

Question

Java shortcut files

Navigation

#1 by (1 votes)

6

What I need to know is why when I enter a record to read, I skip the exception EOF that says there are no more records in the file. I have created in the code that each record that has a length of 44 bytes to go directly to a record. Then I wanted to know what my fault is .. I tell him that I want to go to register 1 and I skip the exception. Can you make me an example file, or tell me where the fault is?

import java.io.*;
import java.util.Scanner;
class Principal{
    public static void main(String [] args) {
        int longRegistro, n, id;
        double salario;
        String apellido;
        Scanner lectura = new Scanner (System.in);
        RandomAccessFile entrada = null;
        String nombreFichero;
        try {
            System.out.println("Introduzca el nombre del fichero");
            nombreFichero = lectura.next();
            entrada = new RandomAccessFile(nombreFichero, "r");
            System.out.println("Introduzca el numero de registro a leer");
            n = lectura.nextInt();
            longRegistro = 44; //4 bytes (int), 30(String)+2 UTF, 8(double)
            entrada.seek((n - 1) * longRegistro);
            id = entrada.readInt();
            apellido = entrada.readUTF();
            salario = entrada.readDouble();
            System.out.printf("%d %s %.2f\n", id, apellido, salario);
        }
        catch (EOFException e) {
            System.out.println("\nHa llegado al final del fichero. "    +   "El numero de registro no existe.");
        }
        catch (FileNotFoundException e) {
            System.out.println("El fichero especificado no existe");
        }
        catch(IOException e) {
            System.out.println("Excepcion de entrada/salida:" +
            e.toString());
            System.out.println(e.getMessage());
        }
        finally {
        try {
            entrada.close();
        }
        catch (IOException io) {
            System.out.println("No se ha podido cerrar el fichero" +io.toString());
            System.out.println(io.getMessage());
        }
       } // Fin finally
    } // Fin método main
}

java

asked by gabriel gomez 18.05.2016 в 21:38

source

1 answer

Help with .htaccess - Url Friendly Working with python lists

score 1 · Answer 1

Seeing that you still have no answer and based on the conversation of the comments, I'm going to propose a much simpler and shorter way to read and pause the data of a model file like the one you propose :

FILE: ( datos.txt )

1 Gabriel 10.5
2 Jordi 340.23
3 Javi 432

Principal.java (I've put the option to read the whole file to show you another way to read)

private static final String FOLDER  = "D:\Users\VEMIJCS\_1\";

public static void main(String[] args) throws Exception {
    Scanner in = new Scanner(System.in);
    System.out.print("nombre fichero ");
    String file = in.nextLine();
    System.out.print("fila a leer (0 todas) ");
    int row = in.nextInt(); 
    in.close();

    BufferedReader reader = new BufferedReader(new FileReader(FOLDER + file)); 
    String line = "";

    // mostramos todo el fichero
    if (row == 0) {
        while ((line = reader.readLine()) != null) {
            print(line);
        }
    } else {
        // leemos hasta la linea que nos han pedido
        for (int i = 0; i < row; i++) { 
            line = reader.readLine();
            if (line == null) { 
                System.out.println("no existe la linea numero " + row);
                System.exit(0);
            }
        }

        // e imprimimos
        print(line);
    }
    reader.close();
}

private static void print(String line) {
    int numero      = Integer.parseInt(line.trim().split(" ")[0]);
    String nombre   = line.trim().split(" ")[1];
    double valor    = Double.parseDouble(line.trim().split(" ")[2]);

    System.out.println(nombre.toUpperCase() + " ocupa la linea numero: " + numero + " y tiene un valor de " + valor);

}

OUTPUT FOR VALID LINE NUMBER

nombre fichero datos.txt
fila a leer (0 todas) 2
JORDI ocupa la linea numero: 2 y tiene un valor de 340.23

DEPARTURE FOR LINE NUMBER == 0

nombre fichero datos.txt
fila a leer (0 todas) 0
GABRIEL ocupa la linea numero: 1 y tiene un valor de 10.5
JORDI ocupa la linea numero: 2 y tiene un valor de 340.23
JAVI ocupa la linea numero: 3 y tiene un valor de 432.0

DEPARTURE FOR NON-VALID LINE NUMBER

nombre fichero datos.txt
fila a leer (0 todas) 9
no existe la linea numero 9

NOTES

Imports needed:

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;

I have not performed exception control to parsed the data but do not forget to implement it in case the data in the file is not correct.
The file must be located in the corresponding FOLDER directory.
If you have any questions, contact me :) .