I have a class called SnmpGet.java in default package. it needs a jar called example.jar. the structure of example.jar is -> degault package-> snmp.class. now SnmpGet.java makes use of this snmp.class. So now it works fine because SnmpGet.java and snmp.class are in default package. But if i move the SnmpGet.java in user defined package like com.test.Work it is not able to detect jar file. what can i do?
I need to use SnmpGet.java in user defined package only. And the jar is the downloaded one. I can not make changes to it.
First, your package does not follow the java naming conventions, no upper cases !
Do you rely on protected methods, classes, attributes...etc of snmp class ? If so, then moving your SnmpGet class to another package will cause you to lose these accesses
You may please try to add the jar(s) dependencies to your classpath. And import the packages & classes from the jar(s) that you would like to use in your SnmpGet.java file. If you are using NetBeans IDE do the following settings to add your jar(s) to your class path:
Right-click on your project folder.
Go to Properties -> Libraries -> Add JAR/Folder.
Add all the jar(s) files to your classpath.
Click on OK to finish the process.
If you are working on Eclipse IDE, you may use the following steps:
Right-click on your project folder.
Go to Properties -> Java Build Path.
Select the Libraries tab -> Add External JARs
Add all the jar(s) files to your classpath.
Click on OK to finish the process.
Hope this resolves your issues.
If you want to call protected methods of snmp.class then your class has to
subclass snmp.class (public class SnmpGet extends snmp) or
be in the same package as snmp.class
Moving the java file from . to directory ./com/test/Work requires to add a package statement to the source file:
package com.test.Work;
Then it has to be compiled (again).
Now, in order to start the application, go back to directory . (the one that contains the com folder now) and do a
java -cp .;example.jar com.test.Work.SnmpGet
(use : instead of ; if you use unix)
Related
I would like to make a Java package in a JAR file with precompiled classes such that other Java projects can consume these. How do I do that? It seems to me that most guides I have found expects a Main class/method to be available, but I do not want this to be an application that runs by itself. Furthermore, the resources (various files) inside of my project should be put into the JAR, since my app depends on these. Is this possible? I am (by the way) using Gradle.
A claim has been made that this question is a duplicate of this: Java creating .jar file. However, this question assumes the existence of main methods, and it does not concern how to include resources.
You can create the jar from the command prompt.
Copy all the classes that you want to include into a folder.
Then open that folder in command prompt and issue this command.
jar cfv YourProjectName.jar *
And a JAR will be created in the same folder containing all the classes.
Another solution:
If you are using eclipse try:
Right Click on the Package -> Export -> java -> jar file
You could also select the Classes and right click on them instead of the Package.
Edit:
Refer to https://docs.oracle.com/javase/tutorial/deployment/jar/build.html for more details on this command.
you can put all your methods/functions in class file then export it to .jar
then add the jar to your project's build path. Now you should be able to call those functions from your current main java class.
I have web application that is running in Jboss container.
Sometime I need to debug the code and for the I need to know from which jar current class is being referred (so that i could search of source jar of the corresponding jar)
Is it possible to get this Jar information (name of the jar file) from which current class is being referred. See the attached screen shot - from where i am trying to get this jar file information. Not sure if my approach is right or wrong
Eclipse allows you to make code changes during debug time.
So, if you want to entering in a class and know what is the jar source of this class just do CTRL + Mouse Right click in the class name and you enter inside the class.
If you have the "Link with Editor" option selected in your Package Explorer you can see automaticly what is ths jar file you are importing.
Compile time classpath settings are different from Runtime server classpath settings.
So if you want to know all the locations/jars that contain a particular class at compile time in eclipse then use Ctrl+T and type the class name. If there are multiple jar files with same class/namespace, then the order will be defined in Build Path settings --> Order and Export.
Runtime reference depends on class loading policy of your server configuration. But usually first it refers from local project, then manifest and then from common class path library.
If your server is configured to refer the workspace location of your project, then most probably the order would be as you defined in .classpath file, and you can use Ctrl+T to find it out.
Edit
It seems you want eclipse to resolve the source file automatically. If you are using maven then run below commands to refresh the source and javadoc for all your jar files.
mvn dependency:sources
mvn dependency:resolve -Dclassifier=javadoc
I'm trying to learn Java ( I know php ) but I don't know what path the included classes have. For example, I create a new directory in Eclipse (in the package) and drag there a class from other project. When I try to import it, it cannot find the class. Even if I don't have any dirs and the class is directly in the package, using import package.classname doesn't work...
I must be missing something but googling doesn't show me any replies.
How do I get the class path? Is it somewhere in the properties?
Java has the concept of a classpath: a path where all classes should be found.
You can get the existing classpath with this code:
System.getProperty("java.class.path")
If you run java from the command line then you have to set your own classpath with your classes.
From the classpath, use the package to find the class. For example, if the classpath is ".", which is the current folder, and you have a class called A, which is in the package com.yourcompany, then you will find the class under ./com/yourcompany/A.class
On the example you gave, go to the terminal and look for the "bin" folder and you will see all classes. However, if you want to add a new class from another project to your project, then there are simpler ways. You can simply open your build path in Eclipse and add the class from the other project onto your project.
Another way is to create a jar from the other project and add the jar to your project.
In Eclipse, go to Project->Properties-Java Build Path where you can config the classpath which allow you to import.
I use Eclipse IDE for my Java projects and all my projects(Project_1,Project_2 and so on) related classes are inside a package package_name.
I am currently working on 2 classes.
class_name.java(Project_2/package_name)
utility.java(Project_1/package_name)
All methods are public.
How can I use the methods within utility.java in class_name.java ?
You can create a jar file from the source package and import it in the classpath of Project_2.
1- Right Click on desired package -> Export -> JAR File
2- Right Click on goal project -> build path -> Add external jar(or copy the jat file in lib folder of the second project and select the Add Jars in the Libraries tab of Java Build Path)
If only one requires the other, you can use the Java Build Path property page of one project (Project 2) to have it require the other.
I have two jar files - jar1 and jar2. Both of them are located in C:\Eclipse projects\ and I have added the paths to both of them to the Environment Variable CLASSPATH as follows
.;C:\Program Files\Java\jre6\lib\ext\QTJava.zip;C:\Eclipse projects\stdlib.jar;C:\Eclipse projects\algs4.jar
the ".;" at the beginning were there so I left them. Then I added the jars to the project from their location C:\Eclipse projects\ and they showed up as Referenced Libraries. However, when I try to instantiate a class from the jars it does not recognize it. I am also not able to import the jar (import jar1).
After I tried adding a lib folder in the project and I added the jars there. After, I added them as references once again (so not they appear twice in the Referenced Libraries), however, I am still not able to use the inner classes. Any help will be much appreciated.
UPDATE:
Something must be wrong on my end. None of the suggestions worked for me. Here is a video with all the steps: screencast.com/t/gC81YzCsLY0e
RESOLUTION In my project I had a package called TestProject and it seems that those jars needed a default package. After deleting the TestProject package and using a defaultPackage everything worked correctly after adding external JARs as explained below.
I've got the same problem as you today, And no answer from the web can solve it. However, I fixed it at last.
In fact, there is nothing wrong with the setup, it is right to import those jars through "Add External JARs". The real problem is the location/package of you java code. I found that you have to put your .java file in the default package. For example, you will get errors if you put your java code in a package like com.xxx.yyy.ccc, below is an image which shows the right location/package you should use(see WTF.java). After doing that, you program will be able to run.
However, that is how i fixed my problem, i'm not sure that could work for everyone..
In eclipse, right click on a project->Propeties->Java Build Path->Add External JARs (Add JARs if the jar is inside the project's folder) and then choose your jar file.
From now you can use the inner classes of the jars you added. Eclipse will import them when you'll start using them.
Why don't you use these two JARs—— stdlib-package.jar and algs4-package.jar.
And below the code page(http://algs4.cs.princeton.edu/code/)
Q. If I use a named package to structure my code, the compiler can no longer access the libraries in stdlib.jar or algs4.jar. Why not?
A. The libraries in stdlib.jar and algs4.jar are in the "default" package. In Java, you can't access classes in the default package from a named package. If you need to use our libraries with a named package, you can use these package versions: stdlib-package.jar and algs4-package.jar.
Warning: if you are taking Princeton COS 226 or Coursera, Algorithms, Part I or II, you must use the default package verison of our libraries to facilitate grading.
Showing my test success:
If you have a folder with your JAR files into the project:
Right click on the project>Build Path>Configure Build Path;
At the tab "Libraries" click on Add JARs, search and select the JARs files you want to use.
If you have yours JAR files any other place outside the project:
Right click on the project>Build Path>Configure Build Path;
At the tab "Libraries" click on Add External JARs, search and select the JARs files you want to use.