Accessing a file using Properties

Question

I am working with a method that takes as argument an object from the Properties class:

public static void main(String[] args) {
        //Properties props = new Properties();
        Properties props = new Properties();
        props.setProperty("TREINAMENTO.txt", "E:\\USER\\Documents\\Interface");

    }

In the setup method, I have:

public void setUp(Properties props) {


        props.getProperty("TREINAMENTO.txt", "E:\\USER\\Documents\\Interface");

        }

I need to access the TREINAMENTO.txt file, which has the format of a double matrix, and put it into a training variable[][]. How can I do this? I don’t quite understand how the Properties class works.

Answer 1

Properties, are configuration files that work with pairs of chave and valor - these keys and values are always Strings.

You use the chave to recover the valor that you save in this configuration file.

Here’s an example of how to read your file (put it in your project folder):

import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

public class LerPropriedades {
    public static void main(String[] args) throws IOException {

        FileInputStream in = new FileInputStream("TREINAMENTO.txt");
        Properties propriedades = new Properties();
        propriedades.load(in);
        in.close();

        for(String chave : propriedades.stringPropertyNames()) {
              String valor = propriedades.getProperty(chave);
              System.out.println(chave + ": " + valor);
            }
    }
}

You can also try creating a property file to see how it should be structured in this way:

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;

public class SalvarProperties {
    public static void main(String[] args) throws IOException {
        Properties propriedades = new Properties();

        propriedades.setProperty("0", "1.14");
        propriedades.setProperty("1", "132.495");

        FileOutputStream out = new FileOutputStream("TREINAMENTO.txt");
        propriedades.store(out, "---comentario---");
        out.close();
    }
}

If you want to put the read information on array, you can do it this way (sorry, I don’t know how to do it better):

Double meuArray[][] = new Double[10][2];
int counter = 0;

for(String chave : propriedades.stringPropertyNames()) {
    String valor = propriedades.getProperty(chave);
    meuArray[counter][0] = Double.parseDouble(chave);
    meuArray[counter][1] = Double.parseDouble(valor);
    counter++;
}

Just replace the loop for of LerPropriedades by that code. I used the following file to test:

#TREINAMENTO
#25/05/2017
0=2.43
1=1.2343
2=15.32
3=80.55
4=532.0
5=943.1
6=9.0
7=3.00038
8=65.12
9=200.01

See here more information