little clean up in the code

src/application/Main.java

@@ -1,5 +1,6 @@
 package application;
 
+import application.client.view.ResourceLoader;
 import javafx.application.Application;
 import javafx.fxml.FXMLLoader;
 import javafx.scene.Parent;

src/application/PropertiesLoader.java

@@ -1,6 +1,8 @@
 package application;
 
 
+import application.client.view.ResourceLoader;
+
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -8,8 +10,11 @@ import java.io.OutputStream;
 import java.util.Properties;
 
 public class PropertiesLoader {
+    public static final String CONFIG_NAME_FILE = "config.properties";
+
     private static final PropertiesLoader instance = new PropertiesLoader();
     private ResourceLoader resourceLoader = ResourceLoader.getInstance();
+    private Properties properties = null;
 
     public PropertiesLoader () {}
 
@@ -18,23 +23,21 @@ public class PropertiesLoader {
     }
 
     public Properties load() {
-        Properties properties = new Properties();
-
+        this.properties = new Properties();
        try {
-           InputStream inputStream = resourceLoader.getResourceAsStream("config.properties");
-           properties.load(inputStream);
+           InputStream inputStream = resourceLoader.getResourceAsStream(CONFIG_NAME_FILE);
+           this.properties.load(inputStream);
 
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
-
-        return properties;
+        return this.properties;
     }
 
     public void save(Properties prop) {
         try {
-            OutputStream output = new FileOutputStream(this.resourceLoader.getPath("config.properties"));
+            OutputStream output = new FileOutputStream(this.resourceLoader.getPath(CONFIG_NAME_FILE));
             prop.store(output, null);
 
             output.close();
@@ -43,4 +46,12 @@ public class PropertiesLoader {
             e.printStackTrace();
         }
     }
+
+    public String get(String name) {
+        if (this.properties == null) {
+            this.load();
+        }
+
+        return this.properties.getProperty(name);
+    }
 }

src/application/client/view/ResourceLoader.java

@@ -1,18 +1,19 @@
-package application;
+package application.client.view;
 
 import java.io.InputStream;
 import java.net.URL;
 
 public class ResourceLoader {
     private static final ResourceLoader instance = new ResourceLoader();
+    public static final String RESOURCE_FOLDER = "resource/";
     String name;
 
     public URL getResource(String name) {
-        return getClass().getClassLoader().getResource("resource/" + name);
+        return getClass().getClassLoader().getResource(RESOURCE_FOLDER + name);
     }
 
     public InputStream getResourceAsStream(String name) {
-        return getClass().getClassLoader().getResourceAsStream("resource/" + name);
+        return getClass().getClassLoader().getResourceAsStream(RESOURCE_FOLDER + name);
     }
 
     public String getPath(String name) {

src/application/client/view/mainPage/MainPageController.java

@@ -1,4 +1,4 @@
-package application;
+package application.client.view.mainPage;
 
 import application.client.Connector;
 import application.client.exception.CannotConnectException;

src/resource/mainPage.fxml

@@ -7,7 +7,7 @@
 <?import javafx.scene.layout.VBox?>
 <?import javafx.scene.text.Font?>
 
-<VBox prefHeight="400.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.MainPageController">
+<VBox prefHeight="400.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.client.view.mainPage.MainPageController">
   <children>
     <AnchorPane maxHeight="-1.0" maxWidth="-1.0" prefHeight="-1.0" prefWidth="-1.0" VBox.vgrow="ALWAYS">
       <children>