You are not breaking OOP principals. However, you are breaking principals of functional programming. Functional programming views leaking of access as losing of control.
Whether or not you want to practice functional programming is up to you, Java doesn't take a stance in that matter.
You may want to consider if it's important not to leak access for this particular class. If you find it important not to leak access then make this class immutable.
You can also guard the instance variables. In this scenario any possible changes to the variables must be handled by the instance class. However, the instance could be modified from separate contexts and result in loss of control. For this reason functional programming only allows immutable classes.