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How to correctly create and import packages in Java

I am using Netbeans 8.1 and Java 8.
I have a Java program named "MyFrame.java" and I want to create a package with its classes and methods - I call this package "myframe" and it is located at "\Lab\MyFrame\src\myframe". See picture:
(Ignore the red lines - this is a dummy version).
The class file is created after compiling, using the command "javac MyFrame.java", in the same directory \myframe. Now I want to import the package "myframe" in a new Java file "MoreButtons.java". So it would look like this and for convenience I save it in \src:
Compiling and executing MoreButtons.java works fine. The package has been imported. But now MyFrame.java is a bit trickier to execute: the naïve approach yields:
Translation: Error: Could not find or load main class
This seems to be quite a common problem and one of the solutions is simply to add the directory (\myframe) to the PATH environment variable. However, doing this still produced the error.
1) What am I doing wrong and how can I fix this?
2) What is the correct way to create and import custom-made packages in Java?

Make sure that terminal is at path Lab\MyFrame\src:
javac myframe\MyFrame.java MoreButtons.java
java -cp .; myframe.MyFrame
P.S. (/,:=linux/mac) or (\,;=windows)
MyFrame.java
package myframe;
public class MyFrame extends javax.swing.JFrame{
public MyFrame(String title){
super(title);
setSize(200,100);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}
}
MoreButtons.java
public class MoreButtons {
public static void main(String[]args){
new myframe.MyFrame("More Buttons");
}
}

How do I load an external jar file in a Applet?

So I am working on a project in C# but in order for me to progress I need to get my jar file to run.
This is the jar file
The jar file is a game called Runescape and if I were to double click that jar file it won't do much so I was looking at this example
Applet applet = (Applet)classLoader.loadClass("client").newInstance();
applet.setStub(stub);
applet.setSize(new Dimension(763, 504));
applet.init();
applet.start();
i.add(applet);
i.pack();
i.setDefaultCloseOperation(3);
label.setVisible(false);
Which by the looks of it takes the jar file and runs it in a Applet to give the user a visual representation of the game.
And thought it could be of help.
Now since I am a C# developer with minor Java experience I find it hard to know where to start, I have IntelliJ installed and ready to create a project but what do I need to do in order to get that jar file to run in a Applet so I can later on compile that project and use it a "client" for the game?

Running an applet from an Application is actually not that easy (and not partucally recommended).
I wrote a litte test for your jar file and run into an issue which I belive is that I am missing a proper AppletStub
import javax.swing.*;
import java.applet.Applet;
import java.awt.*;
import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
class appletrunner
{
public static void main(String[] args) throws Exception //This is not proper Exception handling!
{
JFrame frame = new JFrame("test");
File jar = new File("gamepack_8614663.jar");
URLClassLoader classLoader = new URLClassLoader(new URL[] {jar.toURI().toURL()}, appletrunner.class.getClassLoader());
Class<?> client = classLoader.loadClass("client");
Applet applet = (Applet)client.newInstance();
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
applet.stop();
applet.destroy();
}
});
frame.getContentPane().add(applet);
frame.pack();
frame.setVisible(true);
applet.init(); // Exception here
applet.start();
}
}
This Fails on applet.init() with a cryptic Exception (caused by the obfuscator used by runescape jar). But I think with a proper AppletStub which itself requires a AppletContext it could work.
You could try implementing a class for these interfaces and add them to the applet with addStub(). Hope this is somewhat helpfull.

UnsatisfiedLinkError in exported (Eclipse) executable jar file

The code works fine when executing from Eclipse. I'm using OpenCV 2.4.11 and JavaFX for UI. When I export an Executable Jar from Eclipse and run it from cmd I get the following exception:
I followed many post here on SO and OpenCV forum(1, 2, 3, 4) but, none of the answers seems to help me.
I have added the OpenCV jar as library and Native Library is linked to /build/java/x64 as suggested in SO answers.
The exception occurs at the System.loadLibrary(Core.Native_Library_Name), I checked the Native_Library_Name and the OpenCV version is same as the one I imported in my project.
public class CustomFrame extends Application{
#Override
public void start(Stage primaryStage){
Group root = new Group();
Canvas canvas = new Canvas(1440, 840);
ImageView imageView = new ImageView();
imageView.setFitHeight(canvas.getHeight());
imageView.setFitWidth(canvas.getWidth());
new FrameController().startCamera(imageView);
root.getChildren().addAll(imageView, canvas);
primaryStage.setScene(new Scene(root));
primaryStage.show();
}
public static void main(String[] args)
{
// load the native OpenCV library
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
launch(args);
}
}
If anybody thinks that I have missed something please do let me know.

The UnsatisfiedLinkError is thrown when an application attempts to load a native library like
.so in Linux,
.dll on Windows or
.dylib in Mac
and that library does not exist.
Specifically, in order to find the required native library, the JVM looks in both the PATH environment variable and the java.library.path system property.
Sometimes if the native library was already loaded by an application
and the same application tries to load it again, this can cause this
error also.
How to deal with the UnsatisfiedLinkError?
First of all we must verify that the parameter passed in the System.loadLibrary method is correct and that the library actually exists. Notice that the extension of the library is not required. Thus, if your library is named SampleLibrary.dll, you must pass the SampleLibrary value as a parameter.
Moreover, in case the library is already loaded by your application and the application tries to load it again, the UnsatisfiedLinkError will be thrown by the JVM. Also, you must verify that the native library is present either in the java.library.path or in the PATH environment library of your application. If the library still cannot be found, try to provide an absolute path to the System.loadLibrary method.
In order to execute your application, use the -Djava.library.path argument, to explicitly specify the native library. For example, using the terminal (Linux or Mac) or the command prompt (Windows), execute your application by issuing the following command:
java -Djava.library.path= "<path_of_your_application>" –jar <ApplicationJAR.jar>
You have missed the actual command. Use the following
java -Djava.library.path="C:\Opencv2.1.11\opencv\build\java\x64" -jar BlurDetector.jar
or
java -Djava.library.path="C:\Opencv2.1.11\opencv\build\java" -jar BlurDetector.jar
instead of your command
java -Djava.library.path="C:\Users\vivek_elango\Desktop" -jar BlurDetector.jar // you have given wrong path of your application

It looks like you need to add the path containing the opencv-2411 native libraries to the -Djava.library.path when running from the command prompt.
So something like this:
java -Djava.library.path="C:\Opencv2.1.11\opencv\build\java\x64" -jar BlurDetector.jar

In opposite to the other answers, I rather suggest you never use absolute paths, instead use relative ones. When you give your software to another user, the user most certainly won't have the libraries in the same path as you do. By using relative paths in regards to your application you guarantee that the software runs on other users systems as well, without them having to set path variables, jvm directives and what not. They don't even have to have OpenCV installed if you give them the library dll this way.
Here's code to load the libraries in a relative way:
public static void initOpenCv() {
setLibraryPath();
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
System.out.println("OpenCV loaded. Version: " + Core.VERSION);
}
private static void setLibraryPath() {
try {
System.setProperty("java.library.path", "lib/x64");
Field fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths");
fieldSysPath.setAccessible(true);
fieldSysPath.set(null, null);
} catch (Exception ex) {
ex.printStackTrace();
throw new RuntimeException(ex);
}
}
All you have to do is to
put the libraries into a lib/x64 folder relative to your jar file
in your application you have to invoke initOpenCv() at the start of your program
That's it. This way you can develop as before and maintain a distributable application.
Here's the full version:
import java.lang.reflect.Field;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
import org.opencv.core.Core;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
initOpenCv();
HBox root = new HBox();
Label infoLabel = new Label();
infoLabel.setText("OpenCV loaded. Version: " + Core.VERSION);
root.getChildren().add(infoLabel);
Scene scene = new Scene(root, 400, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void initOpenCv() {
setLibraryPath();
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
System.out.println("OpenCV loaded. Version: " + Core.VERSION);
}
private static void setLibraryPath() {
try {
System.setProperty("java.library.path", "lib/x64");
Field fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths");
fieldSysPath.setAccessible(true);
fieldSysPath.set(null, null);
} catch (Exception ex) {
ex.printStackTrace();
throw new RuntimeException(ex);
}
}
public static void main(String[] args) {
launch(args);
}
}
With a folder structure like this:
.\application.jar
.\lib\x64\*.dll
Hint: I packaged the opencv jar into the application.jar

Null Pointer Exception in GLProfile with JOGL 2.0

JOGL 2.0 added a GLProfile parameter to GLCapabilities. For whatever reason, with this simple code:
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLProfile;
import javax.media.opengl.awt.GLCanvas;
public class Test {
public static void main(String[] args){
GLCanvas canvas = new GLCanvas(new GLCapabilities(GLProfile.getDefault()));
}
}
I get the following error:
Exception in thread "main" java.lang.NullPointerException
at javax.media.opengl.GLProfile.getProfileMap(GLProfile.java:1561)
at javax.media.opengl.GLProfile.get(GLProfile.java:589)
at javax.media.opengl.GLProfile.getDefault(GLProfile.java:421)
at javax.media.opengl.GLProfile.getDefault(GLProfile.java:429)
at com.setcorp.mosey.Test.main(Test.java:7)
So I cannot even create a GLCanvas for use in my JOGL 2.0 application.
Substituting in:
GLCanvas canvas = new GLCanvas(new GLCapabilities(GLProfile.get(GLProfile.GL2)));
or
GLCanvas canvas = new GLCanvas(new GLCapabilities(null));
for line 7 gives me the same error.
I have set the build path to include newt.all.jar, jogl.all.jar, nativewindow.all.jar, and gluegen-rt.jar. I unzipped the dlls from their native jars and set the native library locations respectively in eclipse. I am using the jogl-2.0-b409-20110717-windows-i586 build and running W7, Intel Core 2 Duo T8100 2.10GHz, 2GB RAM, and Nvidia Quadro NVS 140M.
Is there an earlier build that would work for me?

Your code seems fine. Just try it with only these jars in your build path (see below). Avoid including other jars when you try it.
jogl.all.jar
jogl-all-natives-windows-i586.jar
gluegen-rt.jar
gluegen-rt-natives-windows-i586.jar

jar could not find main class, despite manifest

I am attempting to put my Java applet into a .Jar so I can sign it, as currently it works locally but throws access denied exceptions when I attempt to run it remotely (it reads other files in the directory).
I created the manifest file correctly when creating the jar and checked it:
Manifest-Version: 1.0
Created-By: 1.6.0_25 (Sun Microsystems Inc.)
Main-Class: netApp
netApp was an applet and runs fine, and it does contain a main method:
import java.awt.*;
import jv.geom.PgElementSet;
import jv.object.PsMainFrame;
import jv.project.PvDisplayIf;
import jv.viewer.PvViewer;
import jv.loader.PgJvxLoader;
import jv.project.PgJvxSrc;
import jv.project.PjProject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.FileReader;
import jv.loader.PjImportModel;
import jv.project.PjProject;
import jv.project.PgGeometry;
import jv.viewer.PvViewer;
import jv.object.PsDebug;
import java.applet.Applet;
public class netApp extends Applet {
public Frame m_frame = null;
protected PvViewer m_viewer;
protected PgGeometry m_geom;
protected netAppProj myModel;
public void init() {
// Create viewer for viewing 3d geometries. References to the applet and frame
// allow JavaView to decide whether program runs as applet or standalone application,
// and, in the later case, it allows to use the frame as parent frame.
m_viewer = new PvViewer(this, m_frame);
//myModel.addActionListener();
// Create and load a project which contains the user application. Putting code
// in a JavaView project allows to reuse the project in other applications.
myModel = new netAppProj();
m_viewer.addProject(myModel);
//myModel.start();
m_viewer.selectProject(myModel);
setLayout(new BorderLayout());
// Get 3d display from viewer and add it to applet
add((Component)m_viewer.getDisplay(), BorderLayout.CENTER);
add(m_viewer.getPanel(PvViewer.PROJECT), BorderLayout.EAST);
m_viewer.showPanel(PvViewer.MATERIAL);
// Get default display from viewer
PvDisplayIf disp = m_viewer.getDisplay();
// Register geometry in display, and make it active.
// For more advanced applications it is advisable to create a separate project
// and register geometries in the project via project.addGeometry(geom) calls.
disp.addGeometry(m_geom);
disp.selectGeometry(m_geom);
//disp.addPickListener(myModel);
/*until here */
}
/**
* Standalone application support. The main() method acts as the applet's
* entry point when it is run as a standalone application. It is ignored
* if the applet is run from within an HTML page.
*/
public static void main(String args[]) {
netApp app = new netApp();
// Create toplevel window of application containing the applet
Frame frame = new jv.object.PsMainFrame(app, args);
frame.pack();
// Store the variable frame inside the applet to indicate
// that this applet runs as application.
app.m_frame = frame;
app.init();
// In application mode, explicitly call the applet.start() method.
app.start();
// Set size of frame when running as application.
netAppProj myModel = new netAppProj();
frame.setSize(640, 550); frame.setBounds(new Rectangle(420, 5, 640, 550));
frame.setVisible(true);
}
/** Print info while initializing applet and viewer. */
public void paint(Graphics g) {
g.setColor(Color.blue);
//g.drawString("Loading Geometry Viewer Version: "+PsConfig.getVersion(), 20, 40);
g.drawString("Loading Projects .....", 20, 60);
}
/**
* Does clean-up when applet is destroyed by the browser.
* Here we just close and dispose all our control windows.
*/
public void destroy() { m_viewer.destroy(); }
/** Start viewer, e.g. start animation if requested */
public void start() { m_viewer.start(); }
/** Stop viewer, e.g. stop animation if requested */
public void stop() { m_viewer.stop(); }
}
I have tried everything when creating the jar including just doing a:
jar cfm app.jar Manifest.txt *.*
When I try and run the jar from windows explorer or by running:
java -jar app.jar
it fails. with the generic error:
Could not find the main class: netApp. Program will exit.
netApp.class is definitely in the Jar.
Thanks in advance for your help.

Given the error message, it looks like it´s got the manifest correctly, but not the class itself. Run jar tvf app.jar to have a look.
Your jar command looks a little off to me... shouldn´t it be
jar cfm app.jar manifest.txt *.*
?