External data ordering

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External data ordering

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#1 by (0 votes)

0

My problem is this:

I have a .csv file in which are stored the attributes of an object which are: CP, Street, number, colony, recipient I want to sort these attributes based on the CP with the following code:

public class ExternalSort {

static int N = 2000000; /** size of the file in disk */
static int M = 100000;  /** max items the memory buffer can hold */

public static void externalSort(String fileName)
{
    String tfile = "temp-file-";
    int[] buffer = new int[M < N ? M : N];

    try
    {
        FileReader fr = new FileReader(fileName);
        BufferedReader br = new BufferedReader(fr);
        int slices = (int) Math.ceil((double) N/M);

        int i, j;
        i = j = 0;
        /** Iterar a través de los elementos del archivo */
        for (i = 0; i < slices; i++)
        {
            /** Leer fragmentos de M-elementos a la vez desde el archivo */
            for (j = 0; j < (M < N ? M : N); j++)
            {
                String t = br.readLine();
                if (t != null)
                    buffer[j] = Integer.parseInt(t.substring(0,4));
                else
                    break;
            }
            /** Sort M elementos */
            Arrays.sort(buffer);

            /** Escriba los números ordenados en el archivo temporal */
            FileWriter fw = new FileWriter(tfile + Integer.toString(i) + ".txt");
            PrintWriter pw = new PrintWriter(fw);
            for (int k = 0; k < j; k++)
                pw.println(buffer[k]);

            pw.close();
            fw.close();
        }

        br.close();
        fr.close();

        /** Ahora abra cada archivo y combinelos, luego vuelva a escribirlos en el disco */
        int[] topNums = new int[slices];
        BufferedReader[] brs = new BufferedReader[slices];

        for (i = 0; i < slices; i++)
        {
            brs[i] = new BufferedReader(new FileReader(tfile + Integer.toString(i) + ".txt"));
            String t = brs[i].readLine();
            if (t != null)
                topNums[i] = Integer.parseInt(t);
            else
                topNums[i] = Integer.MAX_VALUE;
        }

        FileWriter fw = new FileWriter("external-sorted.txt");
        PrintWriter pw = new PrintWriter(fw);

        for (i = 0; i < N; i++)
        {
            int min = topNums[0];
            int minFile = 0;

            for (j = 0; j < slices; j++)
            {
                if (min > topNums[j])
                {
                    min = topNums[j];
                    minFile = j;
                }
            }

            pw.println(min);
            String t = brs[minFile].readLine();
            if (t != null)
                topNums[minFile] = Integer.parseInt(t);
                else
                topNums[minFile] = Integer.MAX_VALUE;
        }
        for (i = 0; i < slices; i++)
            brs[i].close();

        pw.close();
        fw.close();
    } catch (FileNotFoundException e)
    {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch(NullPointerException ex){
        ex.printStackTrace();
    } 
}


static String generateInput(int n)
{
    String fileName = "external-sort.txt";
    Random rand = new Random();

    try
    {
        FileWriter fw = new FileWriter(fileName);
        PrintWriter pw = new PrintWriter(fw);

        for (int i = 0; i < n; i++)
            pw.println(rand.nextInt(9900) + 100);

        pw.close();
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }

    return fileName;
}

It is supposed that I have to return the file ordered based on the CP but not he does it.

As an example I have the following data:

68148, Sur, 45, Real Casa Blanca (Residential), Juan Gabriel Contreras Caceres

68010, Sur, 57, Elsa (Fractionation), Tomas Prieto Jurado

68045, Oriente, 144, Estrella (Colonia), Jorge Conde Prieto

And the ordered file should look like this:

68010, Sur, 57, Elsa (Fractionation), Tomas Prieto Jurado

68045, Oriente, 144, Estrella (Colonia), Jorge Conde Prieto

68148, Sur, 45, Real Casa Blanca (Residential), Juan Gabriel Contreras Caceres

java-8

asked by Adrian Hernandez Islas 13.11.2016 в 06:46

source

1 answer

Doubts with the remote control in the Android notification bar help with iis error

score 0 · Accepted Answer

If you want to order an object of a class created by you, you can do it like that

implement the Comparable Interface and then implement its compareTo abstract method

import java.util. *;

public class StackOverflow implements Comparable {

private int codigo ;

public StackOverflow(int codigo)
{
    this.codigo = codigo;
}

public static void main(String[] agrs) 
{
    List<StackOverflow> lista = new ArrayList<>();
    lista.add(new StackOverflow(10));
    lista.add(new StackOverflow(3));
    lista.add(new StackOverflow(20));

    System.out.println(lista);
    Collections.sort(lista);
    System.out.println(lista);

}

public int compareTo(StackOverflow o) 
{
    //orden ascendente
    return this.codigo - o.codigo ;

    //orden descendente
    //return o.codigo - this.codigo;
}

public String toString()
{
    return ""+codigo;
}

}

I hope it serves you Greetings.