Develop Reference

VS Code - The import "#####" cannot be resolved

So, i am running a java project which have many library that are available in the current working directory but VS code seems to not recognize these library and giving out error "The import ###### cannot be resolved" ex: The import org.apache.pdfbox.pdmodel.PDDocument cannot be resolved"
here is the image that might help you to know more about it
This is the package that i am working on :
Here the org/apache is the library contain the class file that are need to be imported and FileArrangement.java is the file having the import statements
Error i have been receiving
this is what VS code is been showing
i really need your help because i really don't have any idea how to correct this
I have checked other projects and they are also showing the same result although the import statements for java classes like . java.util.ArrayList doesn't show any kind of error and i have tried to clean java in VS code it also didn't work
i just need to correct this error of VS code to import the classes that i need
No error on java.util package

Putting the libraries in your current working directory does not work for Java, you need to add them to the classpath.
If you're using maven, that manages the classpath for you.
If not, you can manage it in VS Code by executing the Java: Configure Classpath command from the Command Palette (Ctrl+Shift+P).

You can add dependencies via Referenced libraries under the JAVA PROJECTS panel.
Or use java.project.referencedLibraries setting in settings.json.
For example:
"java.project.referencedLibraries": [
"library/**/*.jar",
"/home/username/lib/foo.jar"
]
Details can be found in configure-classpath and manage-dependencies.

Kotlin Extensions - Inflate Custom Views

I'm new to kotlin, I Have an adapter class and I need to inflate a view. but recently I'm facing an error saying "Unresolved reference: R"
Like in the image below :
So, how can I inflate this view? I have imported the following:
import kotlinx.android.synthetic.main.slide_layout.view.*
But I can't figure out what should i do next, I searched everywhere, but they all seem outdated! so what should i do? Thank you!

There are two possible issues i can think of,
The first is a missing import to the R class, if your adapter is in an inner package from your domain package name, i.e.
assume this is the domain package 'your.doamin.package'
if adapter is not in that package i.e. adapter is in 'your.domain.package.adapter'
then you need to import the R class into that file, i.e write this import statement
import your.domain.package.R
That should fix your problem for this scenario
If you have already done '1' above then the other issue is, Sometimes Android studio just misbehaves, so close the file and clean and build your project by first clicking, Build -> Clean Project, once the build is done reopen that file.

For resolving the error unresolved reference: R, you are missing import of your R file. Something like
import packageName.R
For your reference, I am attaching a screenshot of the error and see the commented import.
So check where your R.java resides and import that.

First you check your class import statement in that your R class file imported or not.
import packageName.R
also you can set android studio provide auto import features. if you can enable this feature then all required class automatically import your .kt class

Unfortunately not all answers here can solve your problem, I've been looking for general solutions, you can find them
Here

Java library import difficulty

I'm trying to compile a small test program I have written for a raspberry pi.
The program makes use of the Pi4J library to control the piface add-on board.
What I have done so far is based on the following tutorial: http://www.savagehomeautomation.com/piface
While I can get the above example program to compile within my IDE after setting up the class paths I get compile errors with the one I have made and as far as I can tell the imports are set up in the same way.
It says that each of the following packages does not exist:
import java.io.IOException;
import com.pi4j.component.switches.SwitchListener;
import com.pi4j.component.switches.SwitchState;
import com.pi4j.component.switches.SwitchStateChangeEvent;
import com.pi4j.device.piface.PiFace;
import com.pi4j.device.piface.PiFaceLed;
import com.pi4j.device.piface.PiFaceRelay;
import com.pi4j.device.piface.PiFaceSwitch;
import com.pi4j.device.piface.impl.PiFaceDevice;
import com.pi4j.wiringpi.Spi;
I'm assuming that my problem is relatively simple but I don't really understand how import statements work and it's quite vague topic to search about. I have included some file paths if that helps.
This is where my project resides:
/home/pi/JBerries/relay
and this is where the pi4j library is:
/opt/pi4j
I hope the following image provides some of the information requested, note that the class paths are already set up:

You need to set the CLASSPATH environment variable to /opt/pi4j or the jar file therein. WIthout this the compiler is unable to know where your libary is located and will give you the errors you describe.

If you're using a project in JBerries you need to configure the classpath for the project - the screenshot shows the classpath for single-file compilations only. To edit the project config right-click the root node in the project window and select properties.

Java library class not recognized?

I am importing this following :
import org.apache.lucene.analysis.PorterStemmer
in Java program. The whole package is available in refrenced library.
I tried importing
import org.apache.lucene.analysis.PorterStemFilter
and
import org.apache.lucene.analysis.Analyzer;
both are working fine except the first one mentioned
Can anybody point out why ?!

Package org.apache.lucene.analysis.PorterStemmer is not a public package which is why you cannot import it. If you look at this package inside the library, you'll notice that it begins with class PorterStemmer instead of public class PorterStemmer.

My guess is that you have a different version of the Lucene JAR that doesn't contain the class that's failing to work. Open the JAR with WinZip, 7Zip, or some other tool and see if that class is indeed missing. If it is, you either need to find a version of the JAR that has it or rewrite your code to use an alternative.

Com.Google.Common.*.*... import failure

I'm working on a project and need to use the Predicate interface of google's common.base
I tried importing the google-collect jar at http://code.google.com/p/gdata-java-client/source/browse/#svn/trunk/java/deps
I got the jar, imported it in my library but nothing's there...
Can anyone tell help me to be able to work with this interface?

If you are using eclipse, you need to add the library jar to your build path, as described here.
If you are compiling from the command line, use the -classpath option to add the jar to the path.
Also make sure the case is correct in your import declaration. The import should look like
import com.google.common.base.Predicate;
not
import Com.Google.Common.Base.Predicate;
Also you probably know this already, but the import com.google.common.*.* suggested by your question title is invalid - you can only have one *. (import com.google.common.base.* is OK.)