.classpath file in the eclipse question

Question

In the eclipse directory, there is .classpath file. What's the purpose of this file? I have ant build.xml available, why Eclipse still need its own?

Answer 1

Eclipse has its own mechanism for building your project. The .classpath file contains information that the IDE uses to create the classpath used at build-time, runtime etc. You can directly edit this file if you want but it is created by the IDE based on the settings that you provide via the project properties dialog.

There is Ant integration within Eclipse insofar as it provides you a specific editor for build files, but it can't use any of the information in the build file for its own builders. Ant files are custom, so there is no way Eclipse could know what info to use.