Sentence classification with Lucene

Hi all, I would like to classify a sentence into one or two categories. 
I see this classification roughly this way:

```
unknown:
    example1
    example2
    ...
    exampleN

class1:
    example1
    example2
    ...
    exampleN

class2:
    example1
    example2
    ...
    exampleN

...

classN:
    example1
    example2
    ...
    exampleN

...
```

There are about 25-30 classes.
About 10-30 examples per class.
One sentence can get one or two classes assigned

As far as I understand: this can be done with Lucene Core, should be 
quite a standard functionality.
Can you point me to a Java example for this?

Thanks in advance!