This compilation unit isn't on the build path of Java Project error

Today, I checked out an item from SVN and entered it when I wrote the code. After the compilation unit is not on the build path of Java project error.

The usual items are in the input. Then there will be a corresponding code hint, but this is not. Feeling is very tangled, so found on the internet a lot of information. It's finally settled. First open your project's. project file, if you can not find this file in MyEclipse, ctrl+shift+r together Press, in the popup box directly enter the file name ...

Open the file after entering the code, save the project will have automatic prompt code ....

<?xml version= "1.0" encoding= "UTF-8"?>  <projectDescription>      <name>yourprojectname</ name>      <comment></comment>      <projects>      </projects>      <buildSpec>          <buildCommand>              <name>org.eclipse.jdt.core.javabuilder</name>              <arguments>              </arguments>          </buildCommand>      </buildSpec>      <natures>          < Nature>org.eclipse.jdt.core.javanature</nature>          <nature>org.apache.ivyde.eclipse.ivynature </nature>      </natures>  </projectDescription>

Note Replace your own project name ...

This compilation unit isn't on the build path of Java Project error