Java swing on eclipse oxygen 4.7.3a?

Question

I am trying to use windowbuilder on eclipse oxygen 4.7.3a on macOS highSierra. it installed fine but every time I try to open the design part it displays this error

Eclipse is running under 0, but this Java project has a 1.8 Java compliance level, so WindowBuilder will not be able to load classes from this project. Use a lower level of Java for the project, or run Eclipse using a newer Java version.

I tried everything. like changing the running enviroment, .jre files, try different JDE. nothing working. any suggestions?

Answer 1

Your only short term solution is to use a Java version <= 9.

Initially WindowBuilder did not work with Java 9 for several reasons. See Bug 526098 - WindowBuilder fails to work on Java 9 .

One of those issues was that the the System Property java.version was unexpectedly just "9":

Please check that you have exactly 9.0 JDK, it worked for me with 9.0.1 until I downgraded target JRE to 9.0, which has unusual System.getProperty("java.version").equals("9")

The fixes to get WindowsBuilder working on Java 9 were only completed on 2/21/18, and based on your error it looks like a similar issue exists when running WindowsBuilder using Java 10. I suggest you create a Bug Report with Eclipse .

See also:

• SO Post Eclipse Oxygen Window Builder Error with Java SE 10.0.1 where the solution/workaround was to regress to Java 9.
• This Eclipse Forum post where a user is reporting a similar problem to yours.

Answer 2

Uninstall Java Version and Install lower version of Java(8).Support for WindowBuilder is not provided anymore.

How to uninstall current version?(Mac)

Go to /Library/Java/JavaVirtualMachines/ to see current version of java and replace jdk1.8.0_131.jdk with yours.

1. sudo rm -rf /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk
2. sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefPane
3. sudo rm -rf /Library/Internet\\ Plug-Ins/JavaAppletPlugin.plugin
4. sudo rm -rf ~/Library/Application\\ Support/Oracle/Java

Install Java 8 :

https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

Then: Right click on your project and go to Properties

Make sure your configuration look like this, At the top of picture Configure Workspace settings click on it (Uncheck project specification settings) and then see image below

Apply same as in picture Then enable "project specification settings"

Restart Your Eclipse

Done!!