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Visual Studio Code - Java - Import Errors and More

Just starting working on an existing project at work and wanted to use Visual Studio Code as my IDE (I have used it for a recent Rails project and loved it, so wanted to try with Java).
However, whenever I try to open one of the projects I receive a ton of different errors including:
When importing java.io, java.util, or anything similar, the error:
"The import of java.io (or java.util) cannot be resolved"
Existing classes have an error:
"The implicit super constructor is undefined for default constructor. Must define explicit constructor"
Other random "cannot resolve to a type" errors.
All of these seem to stem from some sort of setting error I have with VS Code but can seem to find what it is. I have already uninstalled and reinstalled the RedHat plug-in that enables the Java language for VS Code.
I have tried setting the java_home setting in the extension to the direct location of the install but that didn't work. Tried uninstalling and reinstalling java and that also didn't work.
My operating specs are as follows:
OS: macOS Sierra
VS Code version 1.15.1
JDK version 1.8.0.144
Any idea on what may be causing this? Do you think it may be an error in how I have VS Code set up or if it's an error (or rather incompatibility) with how the existing project is set up?

I ran into a similar issue. The solution was to remove everything from VS Code's workspace storage directory, which was located at $HOME/Library/Application Support/Code/User/workspaceStorage/.
I found this solution here: https://github.com/redhat-developer/vscode-java/wiki/Troubleshooting#clean-the-workspace-directory
Update: This can now be done from within VS Code as of Language Support for Java(TM) by Red Hat Version 0.33.0. Open the command palette and type "java clean" (see official description in link).

As already mentioned previously, you require to clean the project, but that is a bit difficult thing because every folder is a Guid, and you do not know which one to clear, thus requiring you to delete everything. Starting with 0.33.0 version of the plugin you can automatically do that from within the IDE as well, use CTRL + Shift + P and type, java clean, and IDE will show you the suggestion tip for, Java: Clean the Java language server workspace. Upon selection, agree and restart the IDE. It will clean the language server workspace for you.
Another approach can be, the Maven tools within the IDE. If you have this plugin installed, you can use the side bar and utilize the Maven project helper options to perform actions like, clean, install, and package etc. For example, here is the project I am having and the options this shows,
That can be used, graphically, to manage your Maven-based projects. Also, this would work with the Java Extension Pack, not sure yet as to how it would behave with other extensions.

For me: CMD + Shift + P
Then type "Java: Clean Java language Server Workspace"
Note: This will reload/restart vscode as well.
Update:
This appears to not fix it anymore for me. In my case I am using a gradle project, and needed to set the rootProject.name in the settings.gradle to be the same as the folder name that the project is in.

I faced this issue after creating a whole Java project in one computer and then trying to run it on another computer.
After doing everything said in the other answers, what really made VS Code compile was to open each single project java file in VS Code and save it (a simple Ctrl + S). Maybe there is a simpler way of doing it, but that is what worked for me and I hope this helps anyone stuck in this issue.

Press ctrl+shift+p
then search 'java clean' and click 'java: clean java language server workspace' then click restart IDE.

I found another simple trick at least to get rid of "cannot be resolved to a type" errors which were coming from older workspaces and wrong project files I guess?. I just ran an empty main(), with the body commented out, while still keeping my local package / import commands at the start - no errors. After commenting in again, the project compiled without errors. Perhaps this refreshing effect might also help in this context?

I had to clean this folder to get it working on Windows
%APPDATA%\code\Local Storage

Java Error when i press button [duplicate]

This error is just bizarre, my code compiles fine, I can see there are no problems with it, yet this error has just popped up. I have tried re-starting NetBeans and there is no additional exception information.
What can cause this?

If it is Netbeans, try to uncheck "Compile on save" setting in the project properties (Build -> Compiling). This is the only thing which helped me in a similar situation.

I guess you are using an IDE (like Netbeans) which allows you to run the code even if certain classes are not compilable. During the application's runtime, if you access this class it would lead to this exception.

It's caused by NetBeans retaining some of the old source and/or compiled code in its cache and not noticing that e.g. some of the code's dependencies (i.e. referenced packages) have changed, and that a proper refresh/recompile of the file would be in order.
The solution is to force that refresh by either:
a) locating & editing the offending source file to force its recompilation (e.g. add a dummy line, save, remove it, save again),
b) doing a clean build (sometimes will work, sometimes won't),
c) disabling "Compile on save" (not recommended, since it can make using the IDE a royal PITA), or
d) simply remove NetBeans cache by hand, forcing the recompilation.
As to how to remove the cache:
If you're using an old version of NetBeans:
delete everything related to your project in .netbeans/6.9/var/cache/index/ (replace 6.9 with your version).
If you're using a newer one:
delete everything related to your project in AppData/Local/NetBeans/Cache/8.1/index/ (replace 8.1 with your version).
The paths may vary a little e.g. on different platforms, but the idea is still the same.

I also got the same error and I did clean build and it worked.

Add selenium-server-standalone-3.4.0.jar. It works to me.
Download Link

Recheck the package declarations in all your classes!
This behaviour has been observed in NetBeans, when the package declaration in one of the classes of the package refers to a non-existent or wrong package. NetBeans normally detects and highlights this error but has been known to fail and misleadingly report the package as free of errors when this is not the case.

I had the same issue with one of my netbeans project.
Check whether you have correctly put the package name on all the classes. I got the same error message because i forgot to put the package name of a certain class (which was copied from another project).

Disable Deploy on Save in the Project's Properties/Run screen. That's what worked for me finally. Why the hell NetBeans screws this up is beyond me.
Note: I was able to compile the file it was complaining about using right-click in NetBeans. Apparently it wasn't really compiling it when I used Build & Compile since that gave no errors at all. But then after that, the errors just moved to another java class file. I couldn't compile then since it was grayed out. I also tried deleting the build and dist directories in my NetBeans project files but that didn't help either.

Organize your code as a maven module.
Once done run the command from terminal
$mvn installl
to check if your code builds fine.
Finally import the project in netbeans or eclipse as maven project.

change the package of classes, your files are probably in the wrong package, happened to me when I copied the code from a friend, it was the default package and mine was another, hence the netbeans could not compile because of it.

I had this problem with NetBeans 8.0.1. Messages about problem in project deleted class. Deleting the ~/.netbeans didn't work. Also I looked for ANY reference to the deleted class in ALL my projects, nothing found. I deleted the build classes, everything. Then, when I started Netbeans again, compile and magically appears the message in Run and into the mother compiled class. I tried the uncheck "Compile on save" Dime solution, and works, but it's not practical.
Finally, my solution was edit and force recompile of the mother class. This way the new .class doesn't contains the message and Run works OK.

Just check the packaging, the simplest answer I can provide is that your package has been mislabeled (within a class).
Also, you may have some weird characters. Try white-flushing the code in a Notepad (or Gedit) and then pasting it into a newly created class with your IDE.

If you are using Netbeans, try to hit the Clean and Build button, let it do the thing and try again. Worked for me!

I had the same problem. My error was the packaging. So I would suggest you first check the package name and if the class is in the correct package.

Implementing my own functional interfaces resolved this for me (so instead of using java.util.function.* just create your own single-method interface with the parameters and return-type you want).

PhoneGap Android "Could not find *.apk" [duplicate]

I know this question has been asked before and I have seen a plethora of solutions out there, yet none seem to work for me. I was able to build my apk without issues until this error started cropping up. I have tried cleaning my project, removing it from the workspace and reimporting it, removing "Java Builder" from my Builders for the project, building the project manually, reordering my java build path. I have no visible compiler issues and no problems exist in my workspace.
I did experience this issue before and solved it once by removing the project form my workspace and re-importing it and another time I solved it by removing "Java Builder" from my java build path. None seem to work this time. I currently have most of the settings set back to default (i.e. java build is checked again).
I am running windows 7 (64 bit) and using jdk1.6.0_21 via Eclipse 3.6.
Any suggestions would be greatly appreciated as I have lost loads of development time troubleshooting this already.
[Update] My locale is English & I have tried removing the debug.keystore, United States as related to issue 834

Please follow these steps; this might help you out:
Right-click your app project and go to Properties
Select Android from left-hand side list
Uncheck the "Is Library" checkbox
If your app project relies on library projects which are in your workspace, those of course need to have the "Is Library" box checked.

deleting the R.Java file in /Gen folder did the trick for me

I tried all the above solutions. but it didn't work.
The solution was to restart eclipse !!!!!!!
hope this will help someone :)

In my case this problem started after eclipse updated the plugin with the v4.0 API release. I fixed it by going to the main preferences for Eclipse and under Android->Build uncheck 'Skip packaging and dexing until export or launch'
Note: if you eclipse gives you the Unknown Command 'crunch' error then follow this post

I've tried to gather the best of other peoples answers into a step by step list of things to try in order:
Check the project is not set as a library:
Go to Project->Properties
Select Android from left-hand side list
Uncheck the "Is Library" checkbox
Clean and rebuild the project - this should delete and recreate the entire gen folder, including the R.java file mentioned in some peoples answers
Check eclipse and all the Android plugins are up to date
Close the project, exit Eclipse, reopen eclipse, reopen the project.
Go to Java Build Path > Projects and check for any incorrect project dependencies
Go to the main preferences for Eclipse and under Android->Build uncheck 'Skip packaging and dexing until export or launch'
Check JAVA_HOME is set correctly. Follow the steps in this article
If you complete the above list, and still haven't solved the issue, please leave a comment, or if you find something else that works, feel free to edit the answer and add your thing in.

Delete the project from your workspace & import again.
This worked for me.
Can't believe similar issue has been there since 2008.
http://code.google.com/p/android/issues/detail?id=834.

i'm no expert, but eclipse on Windows, doing android apps, refuses to create the default.properties file (in the app root directory). I've just copied one from another app and it works fine. Simple contents, for Android 2.2 project it just says (ignoring comments):
target=android-8
fwiw

I was having the same issue as the OP except that all these suggestions did not work. I found a solution for me.
Make sure that "Skip packaging and dexing until export or launch." is selected.
Go to Window -> Preferences -> Android -> Build. Just make sure that option is selected and apply.
I know this does not make a lot of sense, but having it unselected was giving me this error and with it selected it goes away and the apk is installed.
I am using the auto generated ant build script from android and ONLY using it as my build process in eclipse. I am not using any other build methods.

I figured it out. I was referencing JavaSE-1.5 and using JDK 1.6. I changed it to use 1.6 and that appears to fix it.
Seems like through my research that is an overloaded error message that covers a lot of error cases.

I just fixed this by reselecting a default JRE for the execution environment (JRE6 for JavaSE-1.6 in my case). It got unchecked for some reason.

This fixed my problem. I kept getting the console error in eclipse "Could not find com_android_vending_licensing.apk" and even though it didnt seem to effect the way my app ran, it was annoying. So going into the com_android_vending_licensing project properties and unchecking the "is library" option, building the project to produce the needed apk and then going back into the com_android_vending_licensing project properties and re checking the "is library" check box fixed the problem.

Run Eclipse as "Administrator" and then import the project.

None of these things worked for me. I'm trying to access native code through the jni, first with NDK samples. What I found was the build won't run if jarlist.cache is not present in the project bin directory. If I copy one from another project to that location (may need to refresh to see the folder in Eclipse), build works every time.

Clean the project and it will do. Sometimes it happens unknowingly but keep trying to solve using diff methods.

I had somehow done a Run configuration as a Java application instead of a Android.

the problem for me was I was trying to use IBM RAD which appears to not work properly for this, I installed Eclipse and now have a different error but I should be able to get past it

On my machine (Windows7, 64bit) I could fix this by setting my execution environment to a 32bit variant of the jdk (I used 1.6.0_23). And I tried a lot of things before...

SHA1's answer did it for me: after updating to the latest sdk/adt, my project refused to build an apk; unchecking the option resolved the issue.
I don't know if the update checked this, or if it was checked before but the new adt screwed things up, but things work again now :)

In my case this worked :
Delete R.Java file in /Gen folder
+
Delete all "R.Android" imports that Eclipse added to some of my java classes !!!
and rebuild the project.

remove -- R.java -- Clean the project and run again.. this worked for me ..

Find the project's folder in your system, enter it's Properties via context menu and deselect "Read only" option. Worked in my case.
This seems to be the source of the problem in many cases, moreover some solutions up there base on copying/rewriting the files in the project what makes them non-read-only.

This is caused by JAVA_HOME not being set correctly. It can be easily resolved by following the steps in this article.

Mine was caused by this problem (incompatibility between ADT and SDK), and was fixed thus:
Eclipse > Help
Install New Software
Add 'https://dl-ssl.google.com/android/eclipse/' to 'Work With'
section and press enter
After developer tools appears on the list, check it and click Next
Restart eclipse once download is finished

I my case, I had to switch from API 21 to API 19, clean and build and everything was fine again. I am using a Mac and apparently API 21 is not fully supported on Yosemite.

How do you use a Java project in your Android project in Eclipse?

I'm writing an Android application and there's some Java code in it that's somewhat sophisticated and therefore hard to verify the correctness of in the Android environment. I would like to run this code in a desktop environment where I have more tools with which to examine the output of this code while still using it in my Android application.
My attempted solution is to have three different projects in Eclipse. My Android project and two plain (non-Android) Java projects. One Java project has the sophisticated code that I want to use in Android and the other is a test program that verifies the correctness of the former project. The latter project has already been useful in debugging the former.
However, so far, my attempts to use the Java project in my Android project appears to work in the IDE but when I actually run the Android application, the NoClassDefFoundError exception is thrown whenever I try to access any of the classes. Obviously, that code is not being recompiled into the .dex file but why not?
I could go into detail about what I've done so far but I can't help but think that what I'm doing is a pretty standard and simple thing and there's a plain way of doing it, even though I can't find anyone doing quite what I'm trying. Can someone describe to me how this is done?

Luckily, I found the answer to my own question and I thought I'd share it here to help others in the same situation. It turned out to be very simple...
What I was already doing would have normally worked, which should have been a big clue to me since I have actually done this before, successfully. All you have to do is, under your Android project's Properties > Java Build Path > Projects, add the plain Java project to your "Required projects on the build path" and then under Properties > Java Build Path > Order and Export, check the checkbox of that same project in the "Build class path order and exported entries" list and everything should just work.
From within Eclipse, there's nothing else you need to do to get this setup to work. It's only when you're compiling from the command line that you need to build Java Jars and import them as libraries but I'm not doing that (yet).
Finally, this wasn't working for me because I just happened to be compiling my plain Java project under JDK 1.7 compliance, while my Android project was compiled under JDK 1.6. This is verified by the output on the Console pane, reporting "Dx bad class file magic (cafebabe) or version." This error message goes away when both projects are compiled under the same compliance level and, not coincidentally, the Android program runs properly.
Thank you to everyone who tried to help and I hope this answer is helpful to someone out there!

Would it not work if you made your other plain java project into an Android project and use it to monitor the output on the device?

Thinking in java library installation

Hi i've been trying to install the library on Thinking in Java book 4th edition and i hit a very thick brick wall. I've done everything that the guide from the website told me to do and i still can't get the library to work. From what i've read it seems that the problem is from the build.xml files. having no xml knowledge I am clueless about how I have to modify it in order for it to work. In both cmd and eclipse I am getting these error
c:\TIJ4\code\build.xml
Build Failed
c:\TIJ4\code\build.xml:59:J2SE5 required
Can anyone tell me what I should do ?
I am using eclipse if there is a simpler solution by using eclipse rather than ant please help me out. It's been a week now and I still can't make it work.

The important thing to do is to realize that your ant file has a specific java requirement.
Something to try that might fix this very easily : I believe you can remove any references to a specific JDK, and if you have a reasonably up to date JDK, the build will succeed.
The definete fix : Look into the exact (line 59) of your build file, and try to satisfy the java version that line requires. Java is generally backwords compatible -- something designed to run in J2SE5 should run in the latest JDK. Its not terribly difficult to update your JDK (just google for instructions on your OS).
The most common mistake I see is that people who have the java run time installed believe they also have the Java SDK as well.

Does this "install the library" means you want to look at the code and run them in your eclipse? If so I can share my experience with you.
First run the Eclipse.py script; this will add package info to the source code
Create a new Java project in Eclipse, and then just copy all the source code folders to the src source folder in eclipse, these folders will then be recognized as Java packages.
You should be able to run the classes with a main function.
You can also configure which java version to use for this project in Eclipse build path. 1.5 or higher will work.