I understand that I need to import the packages in
import com.ericsson.otp.erlang.*;
To run Jinterface in Java, this is not included in Java's default libraries but in Erlang's. How do I access this library? Which path should I use? I've google it but found nothing. I am using Ubuntu 13.10. The above code is not enough for this to work.
If you have done any Java development before, then you know that you should add OtpErlang.jar to your application's class path.
You can do this in the command line, Ant, Maven, Gradle or even in your IDE.
Command line example:
javac -classpath OtpErlang.jar YourGame.java
I use OS X and OtpErlang.jar is under:
/usr/local/Cellar/erlang/R16B03-1/lib/erlang/lib/jinterface-1.5.8/priv/OtpErlang.jar
Keep in mind that you need to include OtpErlang.jar also when you run your game.
Try looking in the Jinterface users Guide, they give an example of compiling the Java code.
Related
I am having a doubt.
My understanding is that jdk has [ jre + development tools (Java, javac, debugger etc.) + source code (src.zip) ].
Now working of java compiler is nothing to do with the running of class file.
If I am compiling a .java file then from where the java compiler is importing the package?
I could find the packages under jre.
If I do not opt to install jre while installing jdk, does that mean I will not be able to compile the java file having import statement?
Please help.
First, as a minor remark, a statement like
import java.util.List;
just introduces an abbreviation, allowing you to use the simple word List later in your code instead of the full class name java.util.List. So it's not so much the import statement itself, but the usage of a class like java.util.List that needs some explanation.
You understand correctly that, to compile your java file, the compiler needs some information about every class you use, and it typically finds this information in some jar file containing that class.
Now, where is this jar file containing the java.util.List class that the compiler reads? You're correct, it comes from the JRE, from the rt.jar that's part of the system classpath (the Java compiler itself is a java program that needs the basic classes itself, so wherever you successfully run javac, you always have an rt.jar available).
If your source code used a class from some other library, you'd have to specify that library on the javac command line, using an option like -cp.
Jdk = JRE + other tools like you mentioned.
When you are compiling your java file and you are using java inbuild library then it uses rt.jar to resolve dependency i.e import statements.
You can refer below link for the difference
What is the difference between JVM, JDK, JRE & OpenJDK?
I'm working on a Java/JRuby project which needs to be able to be able to interact with GAMS. I know we can use the Java API, but I would really like to be able to access it using JRuby if possible, since we're hoping to eventual add a DSL and some other complexity I'm not really excited about having to implement in pure Java.
Following the official Java API documentation for GAMS, I have downloaded and setup everything necessary to run GAMS from the command line, but I can't figure out how to include the GAMS directory in LD_LIBRARY_PATH and still run JRuby irb. When I run
export LD_LIBRARY_PATH=/home/wikk/Downloads/gams24.0_linux_x64_64_sfx
Then try to run irb with JRuby, I get
jruby: /home/wikk/Downloads/gams24.0_linux_x64_64_sfx/libstdc++.so.6: version 'GLIBCXX_3.4.15' not found (required by jruby)
I think this is what the documentation is asking me to do to run a Java program that calls the API, is there maybe some way to set LD_LIBRARY_PATH in irb, but before importing all the Java class files? I can do this successfully if I don't set LD_LIBRARY_PATH, but then GAMS tells me it can't find the main program when I try to create a new GAMSWorkspace object:
irb(main):002:0> ws = GAMSWorkspace.new
Java::ComGamsApi::GAMSException: could not find a GAMS system directory from
your environment variable, please set up properly before running a program!
from com.gams.api.GAMSWorkspace.verifySystemDirectory(GAMSWorkspace.java:335)
Am I doing this wrong? or does the API require some Java feature that isn't implemented in JRuby?
Finally came back to this problem, got it working through some trial and error. I also needed to run jruby with the -J-Djava.library.path=[GAMSDIR]/apifiles/Java/api flag, and add [GAMSDIR]/apifiles/Java/api/GAMSJavaAPI.jar to the classpath.
Once this is all in place, you can run gams models from ruby scripts:
import com.gams.api.GAMSWorkspace
import com.gams.api.GAMSJob
import com.gams.api.GAMSVariable
import com.gams.api.GAMSVariableRecord
import com.gams.api.GAMSWorkspace
ws = GAMSWorkspace.new
j1 = ws.addJobFromGamsLib('trnsport')
j1.run
j1.out_db.get_variable('x').each_entry do |rec|
puts "x(#{rec.get_keys[0]}, #{rec.get_keys[1]}): level = #{rec.get_level}, marginal = #{rec.get_marginal}"
end
I am writing here because it is the only thread related to the GAMS Java API problem.
In Eclipse, you have to go to "Run Configurations" and add two things:
1. (As already said) add a "-Djava.library.path=[GAMSDIR]\apifiles\Java\api\" to VM arguments
2. Go to Environment and SET explicitly a PATH variable to [GAMSDIR]. For some reason seeting path through windows is not working
I'm new to java development, I just want to use javac for my build system. I'm using java to add a feature to a program someone else wrote, specifically involving GeoTiff images.
I found a class online that I would like to use, however I'm having trouble building the class, no matter what I do I get this message:
javac GeoTiffIIOMetadataAdapter.java
GeoTiffIIOMetadataAdapter.java:11: package com.sun.media.imageio.plugins.tiff does not exist
import com.sun.media.imageio.plugins.tiff.GeoTIFFTagSet;
I'm on RHEL5, so I installed the package I thought I needed, jai-imageio-core.x86_64. But the problem persists. I think that I'm not setting some variable corrently (like -sourcepath or something). I would appreciate any help.
You need to include the jar with -cp or -classpath.
So your compile would be like java -cp "<location to jai_imageio-1.1.jar>" <your java class> .
I think you need this jar file.
You can read more about javac here.
Find out where the package installed the jar file with the class you want to import, and add it to the javac commandline in the -classpath. (You then also need to include it in the classpath when your plugin runs; how to do that may depend on the program it plugs into).
I think that I'm not setting some variable correctly (like -sourcepath or something)
This tutorial briefly introduces the usage of environment variables in Java: PATH and CLASSPATH
This one seems to be the most popular answer to various classpath related questions I've seen at online forums: Setting the class path.
To avoid "blind recommendation" I quickly skimmed through it before adding to this answer and, well... it really covers most of what one needs to know to deal with classpath. Pretty good; the reason why I didn't look into it before is that there always has been some guru nearby who explained stuff to me.
Let me start by saying I've been doing professional development work in C++ for about 15 years, and I've done a very small amount of Java on Linux systems. However, I seem to be doing something incorrectly with my Java installation on eclipse.
I have eclipse installed on a Windows 7 machine in C:\tools\eclipse\helios.
I have the Java jdk installed in C:\tools\Java\jdk1.6.0.
The Java jre is installed in C:\tools\Java\jre1.6.0.
In eclipse, I create a java project, and point the project at the jdk folder listed above. In other words, I have the jdk listed as one of the installed JREs and it is the selected JRE.
BTW: I also have Google's android tools and the MotoDev envioronment installed in eclipse, and I can write and build android java code in those projects. Of course, they don't use the jdk.
So, I'm relatively new to Java and I want to start simple, so I created the basic HelloWorld project. I have the following simple code:
package app;
import system; // System not recognized here!!!
public class Application
{
public static void main(String[] args)
{
system.out.println("Hello World!"); // System not recognized here, obviously!
}
}
Anyone have any idea what I'm doing wrong here? There doesn't seem to be anywhere to point to the jdk/lib directory. The jdk looks in jdk1.6.0/jre/lib, which I'm pretty sure isn't going to help me.
Thanks.
System class is present in java.lang package. It's imported by default. So no need to import it like you did. Please bear in mind that it's Java's convention to have class names begin with uppercase characters. Hence System class is with upper case S
Documentation for packages and classes in JDK is available at http://download.oracle.com/javase/6/docs/api/. It's a good idea to refer to this often especially when beginning with Java programming
Maybe you need a capital 'S' for System? And you shouldn't need to import 'System'. It is imported automatically.
It is System and not system. And No need to import it explicitly.
I have a java program that I'm required to compile into a Linux native program using gcj-4.3. This program requires serial port access. The javax.comm api provides serial port access but I'm not sure how to get my compiled java program to use it.
The target box has Java installed, but of course my compiled program isn't running in the JRE...so I'm not exactly sure how I can link in the comm.jar file or how that file can find the .properties file it requires.
I wonder if I can just compile the comm.jar allong with my .jar file and link the two object files together. Can my code then reference the classes in comm.jar?
Thanks in advance for your help!
I'm not an GCJ expert but I have some suggestions (I'm not providing the syntax, this will require some exploration that I didn't perform):
first, I think that you'll have to compile comm.jar into a (shared) library,
then, you'll have to link your code against the library,
finally, use the GCJ_PROPERTIES environment variable to pass properties to the program at invocation time.
The following pointers might be helpful to implement this:
GCJ---The GNU Compiler for Java (great resources IMO, covers all the steps mentioned above)
GCJ – Getting Started (more an intro but still nice)
Compile ActiveMQ with GCJ (more use cases but I don't think they apply here)
And of course, the official documentation :)