I have a really basic question about ant. When I execute the `build.xml` file within `Eclipse` with 

Run as -> Ant Build

Then everything works fine. However, when I try to run the same `build.xml` file from the command line like

ant -f build.xml

Then for same classes I get errors like: 

```
Error: `package com.sun.image.codec.jpeg` does not exist

```

Any ideas, what should I do?

Thanks