Information Hiding

When encapsulating, your fundamental activity is finding ways to hide information that you consider to be implementation details.

If you did not hide this information and you have a large number of consumers1, you would never be able to change those implementation details.

Something to be careful of with respect to this is "side channels." If you use the mechanisms Java gives you to hide a field from people, ..

1

Again, if. These concerns do not apply as much to programs written at smaller scales or programs written within some encapsulation boundary. Don't get too paranoid about needing to hide things.