Eclipse editor won't open

Question

My Eclipse cannot show the editor window.

Error:

Could not open the editor: The editor class could not be instantiated. This

Answer 1

at org.eclipse.core.runtime.Path.(Path.java:183)
at org.eclipse.core.internal.resources.WorkspaceRoot.getProject(WorkspaceRoot.java:181)
at org.eclipse.jdt.internal.core.ExternalFoldersManager.isExternalFolderPath(ExternalFoldersManager.java:90)
at org.eclipse.jdt.internal.core.JavaProject.addToResult(JavaProject.java:2738)
at org.eclipse.jdt.internal.core.JavaProject.resolveClasspath(JavaProject.java:2688)

The stack trace seem to indicate that there is a problem with your classpath.

1. Maybe your JRE is pointing to an invalid location / isn't defined? (Window->Preferences->Java->Installed JREs).
2. Maybe your project contains invalid class path entries? Try to create a new java project and check if that is working as expected. If it works check the classpath of your not working project.

Edit: Another Idea ... launch eclipse on an other workspace. Then create a launch configuration for an "Eclipse Configuration" with the workspace that produces an error. Set a java exception breakpoint for NullPointerException. Start in debug mode and you can inspect the variables to see which path produces the problems.