Write to CSV file from java

I have doubts about how to write to a CSV file from JAVA

I know how to read it, but I have doubts about how to write and what is left by columns

So I'm declaring them, now I want the user to enter them and save them in the File. (I do not know if I am declaring good about (0.2 etc))

    String nombre = st.substring(0,2);
    String dato = st.substring(0,3);
    String hora = st.substring(0,4);
    String fecha = st.substring(0,5);