Introduction

You may import a project from CVS, Subversion or somewhere and you have a lot of red x's, and you did not expect it. Usually this means you have build path problems. For example, a colleague recently followed the tutorial for importing Wonder source into Eclipse and after the Workspace was built he had many red x's. The following error gives a clue

Problem

The problem here is the build path setting. The cause can be as simple as the person who last edited the project has selected a different JVM path. So looking at the build path for the project in this case shows that the JVM cannot be found (which is why the most basic class, java.lang.Object, could not be found)

Solution

Selecting the unbound JVM library and clicking edit shows:

Selecting the default System JVM fixes the problem

Afterwards you may need to do a project (or workspace) clean and rebuild to get rid of all the red x's (aka. build errors)