Unable to find the right JVM options

Question

Alright, first and foremost, I am new to Java, but not to programming. For a personnal project I decided that I should use Slick2D, a graphics library in java, and I am running into one problem I haven't been able to fix for now.

Considering the following:

• I use Netbeans
• I'm currently on linux

From what I understand, slick2d uses lwgjl. I have followed the instructions on the following page: Setting up Slick2D for netbeans

My problem I think is giving my JVM the right options. Currently the ones I set are:

-Djava.library.path=/home/karel/Téléchargements/slick/native/unix

Here is the current error output I get:

run:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no lwjgl64     in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1867)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at org.lwjgl.Sys$1.run(Sys.java:72)
at java.security.AccessController.doPrivileged(Native Method)
at org.lwjgl.Sys.doLoadLibrary(Sys.java:66)
at org.lwjgl.Sys.loadLibrary(Sys.java:87)
at org.lwjgl.Sys.<clinit>(Sys.java:117)
at org.lwjgl.opengl.Display.<clinit>(Display.java:135)
at org.newdawn.slick.AppGameContainer$1.run(AppGameContainer.java:39)
at java.security.AccessController.doPrivileged(Native Method)
at org.newdawn.slick.AppGameContainer.<clinit>(AppGameContainer.java:36)
at jcoinche.client.JcoincheClient.main(JcoincheClient.java:29)
/home/karel/.cache/netbeans/8.1/executor-snippets/run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

My code is as follow (well, the part that needs a library, and doesn't work - it's all tutorial material, by the way. Nothing I made myself):

package jcoinche.client;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.util.Scanner;
import static jcoinche.client.Game.gamename;
import static jcoinche.client.Game.xSize;
import static jcoinche.client.Game.ySize;
import org.newdawn.slick.AppGameContainer;
import org.newdawn.slick.SlickException;

public class JcoincheClient 
{
public static void main(String[] args) 
{
   Socket socket;

   AppGameContainer appgc;
   try
   {
        appgc = new AppGameContainer(new Game(gamename));
        appgc.setDisplayMode(xSize, ySize, false);
        appgc.setTargetFrameRate(60);
        appgc.start();
   }
catch(SlickException e)
{
     e.printStackTrace();
}
}

Game.java:

package jcoinche.client;

import org.newdawn.slick.*;
import org.newdawn.slick.state.*;

public class Game extends StateBasedGame
{

   public static final String gamename = "MyGameName";
   public static final int play = 0;
   public static final int xSize = 400;
   public static final int ySize = 300;

   public Game(String gamename){
      super(gamename);
      this.addState(new Play());
   }

   public void initStatesList(GameContainer gc) throws SlickException{
      this.getState(play).init(gc, this);
      this.enterState(play);
   }

}

Play.java:

package jcoinche.client;

import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.state.BasicGameState;
import org.newdawn.slick.state.StateBasedGame;

public class Play extends BasicGameState
{
  public Play() 
        {

    }

    public void init(GameContainer gc, StateBasedGame sbg)
        throws SlickException 
        {

    }

    public void render(GameContainer gc, StateBasedGame sbg, Graphics g)
            throws SlickException 
        {

    }

    public void update(GameContainer gc, StateBasedGame sbg, int delta)
            throws SlickException 
        {

    }

    public int getID() 
        {
        return 0;
    }  
}

Answer 1

Alright, this is a bit embarassing, but I understood what my problem was and it was a simple misunderstanding of the link I gave (instructions on how to install and use slick2D on netbeans):

In fact, my problem was that, because of the lwgjl.jar and other similar files in the slick2D folder, I thought lwgjl was, in the end, included in the slick folder.

As such, for the last step, I gave to my JVM a path directing it to the slick library folder, while it was, this time, asking for lwgjl files, causing the errors shown above.

I changed that path to the lwgjl/native/linux folder, and everything is now working perfectly. Thanks for your answers, they helped greatly.

Answer 2

The error is telling you of the absence of a file named 'lwjgl64'. You are getting an UnsatisfiedLinkError, which according to the Java Documentation, is:

Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declared native.

Now, are you using Slick2D alone? Or do you have LWJGL and Slick2D? Slick2D is not standalone; you need LWJGL to run it. I suggest getting LWJGL from their site, and add it's native folder to the classpath.

From the Slick2D docs, they write this:

   -Djava.library.path=<lwjgl-X.X path>/native/<linux|macosx|solaris|windows> 

Source

Answer 3

There are a few answers on stack that may help you solve this issue as it is clear from the error that it is caused by a linking error to LWJGL64. One post with a number of solutions here offers a number of solutions, though targeted at the eclipse IDE specifically the general solution applies:

To quote from here @Ben Jackson

LWJGL needs the native components for your particular platform to be in java.library.path. These are in the subdirectory native in the LWJGL distribution and end in .so on Linux, OSX and Solaris and .dll for windows.

Other potential examples solving the error: Setting up natives