Train And Use Classifier Weka In Java

Question

I need to generate a classifier in Java and after use it on others datasets.

I can see using Weka GUI that it generates a Tree using a file Csv.

Now my question is:

1. Which is the best way to generate this Classifier in Java?
2. How can i save it in java, in way to use it to predict?
3. After saved how can i use it in java on others datasets?