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compiled by a more recent version of Java Runtime(class file version 55.0),this version of Java Runtime only recognizes class file versions up to 52.0

I'm stuck with this problem for few days now. I have a Spring Boot application which I've created locally and I want to deploy it to Google Cloud App Engine. I'm using a Cloud Code plugin so that I can deploy from within Intellij. I've been trying to deploy from gcloud CLI but I kept getting errors, so now I'm trying to do the same from within Intellij. This is the error that I'm getting:
I've set everything to java 11 in the project structure, and in the java compiler settings too, my local java version is also 11, what might be the problem?

It's IDE Error.
In android Studio File -> Settings -> Build, Execution & Development -> Build Tools -> Gradle and change Gradle JVM to 11

I've set everything to java 11 in the project structure, and in the java compiler settings too, my local java version is also 11, what might be the problem?
Google is the problem. Specifically, evidently AppEngine itself, or possibly because you configured it that way, is limited to java8 which is end of lifed at this point (but still widely used). v52 is java8, v55 is java11.
Set your stuff to java8, recompile, try again.

Set runtime: java11 in your app.yaml file.

intellij gives error of non-whitelisted class with app engine using java 8

AFAIK App Engine supports all standard java libraries when project uses java 8. For some reason Intellij show this as an error. I can run local development server and deploy this project to app engine and it works ok.
I think I could just disable the check for forbidden code in App Engine but is there something else that would actually be forbidden with java 8 also.
Is this issue with gcloud plugin or intellij...?
Edit:
Added project structure

As per documentation The App Engine Java 8 runtime supports the standard public Java library, so there shouldn't be any limitations.
Ther has been an issue (#CrazyCoder's comment) opened in google-cloud-intellij library which has been resolved in the latest version.

IntelliJ Ultimate 2018.2 build on July 2018 solved the issue

java 8 support for Eclipse Indigo [duplicate]

I just read How to have Eclipse use JDK8 to compile a project?
What i added jdk8 to eclipse as,
From the answers of How to have Eclipse use JDK8 to compile a project?
I tried to Update the JDT/Core, JDT/UI bundles from http://dist.springsource.com/snapshot/TOOLS/java8/e43
But it shows error as,
"Eclipse Java Development Tools Patch for Java 8 Support (BETA)" is not applicable to the current configuration and will not be installed.
"Eclipse Plug-in Development Environment Patch for Java 8 Support (BETA)" is not applicable to the current configuration and will not be installed.
How Can i fix it ?

I can say that Java 1.8 does in fact work with Eclipse Luna ( the beta version released around March 17, 2014) or later. I tried it and it was good.
Also, I noticed that in the Eclipse Marketplace, there are now plugins to install functionality into Kepler to support JDK1.8. I haven't tried the plugin myself though.

This is a old topic but I just wanted to point out that I have searched enough to find that Indigo version can't be updated to S.E 1.8 here the link which is given on eclipse website to update the Execution Environment but if you try it will throw error for Indigo.
Here is the link where the Information about execution environment is given.
This shows the step by step to update Execution environment.
I have tried to update Execution environment and I got the same error.

Jetty IllegalArgumentException when using 1.9.30 GAE

I've been on a very old version of GAE for a long time. Every time I try to update to the latest version I get this error when deploying it to GCP:
java.lang.IllegalArgumentException: Class file is Java 8 but max supported is
Java 7: org/eclipse/jetty/http/BadMessageException.class in C:\Users\XXXXXXXXXXX\
backendservlet\build\exploded-app\WEB-
INF\lib\jetty-http-9.3.2.v20150730.jar
I think jetty comes with GAE so how do I fix this? When I deploy it locally it runs without errors. It also builds without error. This only happens when deploying to GCP.
My appengine instance is on JAVA 7 runtime so maybe that's the issue? How do I change that? I tried deplying with a different version and name and it still didn't work.
Please help.

Looks like jetty (or at least the version you're using) needs Java 8, which is not supported on GAE: Does Google App Engine support Java 8?.

GAE does not yet support Java 8. If jetty is a dependency of your project, you need to use a version that has source 1.7. Otherwise delete C:\Users\XXXXXXXXXXX\
backendservlet\build\exploded-app\WEB-
INF\lib\jetty-http-9.3.2.v20150730.jar

Developing CLDC or J2ME applications under Mac OSX?

I have noticed that Oracle now has released a Java Platform Micro Edition SDK for OSX. It works, it can compile the provided examples and the included phone emulator works too. But how do I compile my own J2ME project from Ant or Eclipse?
There are a lot of related jars but they are all inside the ".app" in the /Applications directory. Eclipse does not like it when I put a toolchain path to inside the ".app".

Have you tried using the EclipseME plugin? It helps integrate JavaME (J2ME) development into Eclipse. Here's a guide for getting it working with Eclipse:
Eclipse ME / Configuration
You'll find plenty of documentation and how tos.
If you don't like EclipseME, I personally found Netbeans very good for mobile development:
Netbeans JavaME Page
Also, you weren't specific in your question, but the link you've provided seems to indicate you want to use MTJ. In that case, use this documentation to guide you through:
Eclipse MTJ - Getting Started

If you want to use ANT I have simply copied over the required jars from the Windows SDK and just used the pre verifier and javac from the osx 3.0 sdk, works well!