Forget Java - how would you do it using your brain? There are things that simply do not translate because they are Oracle specific. Very basic SQL stuff should already be compatible.
Why don't you give some examples of what you would like to "convert" to give a clue what you are really asking.
Is it possible to convert Oracle Sql queries into SQLite queries using java ?
No - assuming you mean automagically.
No - assuming you mean all possible queries.
Yes - assuming you mean queries where the syntax is compatible.
Not needed if you mean queries that have the same syntax.
Even queries that use the same supported syntax will likely perform quite differently.
There is no tool I am aware of that will do the conversion at an acceptable level.