Develop Reference

JDK version 1.8 in the system but JDK 11 on VScode

I have JDK11 and JADK8 both installed on my MacOS. I have changed the JDK default version to 1.8 to make sure GlassFish V5 can be run.
However, the change is not taken place at VSCode, and VSCode terminal keeps on showing JDK11 as JAVA version, which is preventing me from running GlassFish server though VSCode.
How can I fix this?
Thank you

Here you can choose wich version to install.
Edit : as mentionned here
VS Code does not have built-in support for Java projects. You need to install some Java extensions and configure them to specify the correct Java JDK version, which you can do by either setting the JAVA_HOME environment variable or by setting the java.home setting:

It depends on the value of JAVA_HOME environment variable. Check your JAVA_HOME path in the settings.json file.
If it shows Java11, set JAVA_HOME environment variable as per your requirement and restart VSCode. Check How to set JAVA_HOME in Mac permanently?.

Java extension needs jdk11 or recent version to support, so it's required to set jdk11 as java.home in vscode, but it's also achievable to specify other jdk version for project.
Open Command Palette and Search Java: Configure Java Runtime.
Choose JDK8 for Project JDKs.
Choose JDK11 or recent version as
Java Tooling Time.
Don't forget to reload window to make the change effective.
Detailed information please view official docs: Configure JDK

Apache Tomcat Still Looking for Uninstalled Java Version

I have jasperserver running on apache tomcat on a web application. I have Java version 1.4 installed and the correct JAVA_HOME environment variable set. I can get to "myurl:8080" just fine and it shows the apache tomcat page. Originally i installed java 1.8 which seemed to be incompatible for my old version of jasperserver.
I needed to install an older version of Java, so i uninstalled 1.8 and installed 1.4 on my linux instance for my Java App. However, when i try and connect to jasperserver through the app, it seems like it is still looking in the old directory for old java library. How can i configure this to look at my new directory in same location? The error is below.
java.io.FileNotFoundException: /usr/lib/jvm/java-8-oracle/jre/lib/rt.jar
The correct version of java is located below.
/usr/lib/jvm/java1.4.2_18/

Try changing the java_home and jre_home environment variables path,if you update
java version.The environment variables need to be edited.
Here is how to change or edit the environment variables

Can I have two versions of the JDK on my computer?

I'm trying to set the IntelliJ IDEA JDK to version 1.8 (because it's the latest). When I navigate to System/Library/Frameworks/JavaVM.framework IntelliJ IDEA shows 1.6. When I type java -version it shows 1.8. I found that command under "Finding default JDK on OSX" https://www.java.com/en/download/help/version_manual.xml
I'm confused what versions of the JDK I have... and where they are located. Appreciate any help.

Yes, you can. You have JDK 1.6 and 1.8 installed on your computer. According to the Jetbrains website, all their products require Apple JDK 1.6 to be installed in order to run on Mac.
To make IntelliJ IDEA use JDK 1.8, you will need to edit /Applications/<Product>.app/Contents/Info.plist file and change JVMVersion from 1.6* to 1.8* :
<key>JVMVersion</key>
<string>1.8*</string>

To start off java will usually uninstall any version of the JDK when you get an update. Secondly if you want to check to see what version you are running I would go into what ever you are using to program and see what version you are compiling under (For example netbeans or eclipse). If it says 1.8 that is what you are running and same for 1.6. If this is really becoming a super big problem all you have to is uninstall java then re install and it should fix it.

You can have many different versions of Java on your system. In general Java depends on environment variables and the PATH environment variable. Some programs and tools look for tool specific environment variables to allow you to use a specific version of Java for that particular tool.
In the case of IntellJ the link that Eddie B posted in his comment explains how IntellJ determines which "installation" of Java it should use.

start SonarQube server with specific jdk

Is there a way to start the SonarQube server (v. 3.7.4) with an specific jdk?
My case: My java-home is set to jdk 1.8, but SonarQube server has some known problems with 1.8. So I want to start the server with jdk 1.7 (without setting my java-home to 1.7).
I couldn't find anything in the bat-files.
OS: Windows 7; SonarQube server version: 3.7.4

You have to edit the <install_directory>/conf/wrapper.conf file and update the wrapper.java.command property to point to the JDK you want.
Everything is documented in this wrapper.conf file.

wrapper.java.command=C:/Program Files/Java/jdk-11.0.11/bin/java

Upgrade Java version for Web Application

I have a web Application and i need to upgrade java jre version from 6 to 7 .I am using Eclipse as IDE.I tried to update the Jre from eclipse .I have even updated the JAVA_HOME environment variable but i am getting following error
C:\Program Files\Java\jdk1.7.0_55\jre..\lib\tools.jar
Please ensure you are using JDK 1.4 or above and
not a JRE (the com.sun.tools.javac.Main class is required).
In most cases you can change the location of your Java
installation by setting the JAVA_HOME environment variable.
Thanks

Download java hereand install it as a common application.
Then in Eclipse use Window->Prefrences->Java->Installed JREs

#Roman Bondar I guesss OP wanted to know more than just the setting.
Basically, JREs are meant to be downwards compatible, so that you are able to execute java classes compiled with version 6 with a runtime from java 7.
But as always, there may be special cases when things have to be changed, e.g. container or libraries. I remember a case back when I migrated to java 6 that it required a special version of JBoss.
Check out this Oracle blog as a starting point.