Eclipse does not compile the problem

The first case:

 If clicking project->Build does not work, first click clean to clean up the project, and then select Build.

Second case:

The svn project does not compile, and the following error is reported:

The working copy needs to be upgraded
svn: The working copy at 'D:\workspace\xxx'
is too old (format 10) to work with client version '1.8.3 (r1516576)' (expects format 31). You need to upgrade the working copy first.

 First, try the first case;

 Secondly, if the first case doesn't work, just select Team->Disconnect (disconnect svn) and select build again.