I found one great thing Eclipse can do for us. That is to merge multiple projects to one.
If I have multiple child projects, please see the direcotry structure.
MyWorkspace
-----MyProject
----------ChildProject1
---------------.classpath
---------------.project
----------ChildProject2
---------------.classpath
---------------.project
Please notice that there is no project file and classpath file in project MyProject. Now I new a project in Ecipse and specify the anme MyProject. Then the project is created, it will merge the two classpaths file from ChildProject1 and ChildProject2. Then you find the directory structure is like,
MyWorkspace
-----MyProject
----------.classpath
----------.project
----------ChildProject1
---------------.classpath
---------------.project
----------ChildProject2
---------------.classpath
---------------.project
What I think is great thing is Eclipse merge the 2 projects and create a whole project. I is a great behavior.