Here's?an analogy.

Imagine a vending machine. It has a public interface that you can use to buy snacks or drinks. You can insert coins, push buttons, and receive your purchase. However, the internal mechanism of the vending machine, such as the motor, the sensors, and the inventory, is hidden from you. You don't need to know how the vending machine works to use it.

Now, imagine that the vending machine manufacturer wants to improve the design of the vending machine. They want to change the motor, the sensors, and the inventory without affecting the public interface. They can do that, because the public interface remains the same. You can still insert coins, push buttons, and receive your purchase, even though the internal mechanism has changed.

This is similar to the principle of information hiding in Java. A class has a public interface that its clients can use, such as public methods or fields. However, the internal details of the class, such as private methods or fields, are hidden from the clients. This allows the class to change its internal details without affecting its clients, as long as the public interface remains the same.