Given a text string like "apple", I want to obtain a number. So every time I do that with apple I get the same number. How can this be done in java?

Thank you.

**EDIT:** well, I think I didn't explain myself well. I mean an existing Java function that implements a map like this. An example of a function like this would be:
 a->1, b->2, c->3,...

```
apple -> 11616125

```