data access layer for java

can anyone help me how to create DATA ACCESS LAYER in java?
im trying to work on it but i really cant make it.
please help me.thanks.

I know of at least 3 ways to do this.

1) You can sprinkle your code with JDBC calls (package java.sql). Not
the best.
2) You can follow the DAO pattern. The ideal way to do this is to
carefully define your code so that users of this layer don't know - and
don't care - what the implementation is. Very desirable.
3) Integrate a 3rd party solution, such as Hibernate. With Hibernate,
you only need to define your mappings via XML; other than that, it
appears that you work solely with Java objects (if you defined your
mappings correctly, that is). This is best for larger systems.