Question

Everyone knows that Java supports data hiding.

I went for an interview. Then interviewer asked me that if Java supports data hiding by using private as datatype.

He said if we use setters and getters in that class then by using those setters and getters we can get that private data easily.

So how this is supporting data hiding here?

It may be possible that he was trying me catch me in trap. But I could not reply this.

What should I reply for this?

Answer 1

He was arguing that if “Data Hiding” is an OOP principle then aren’t we breaking it by exposing via getters and setters. I think he wanted you to spell out the difference in principle between being able to access a data member directly vs. doing it via a getter or setter. In the former case a client of the class can mishandle the data, assign it a value that the class designer has not designed the class to handle (for example set the age of a student as 500).
In the latter (using a setter) the class designer has imposed certain restrictions on what values can be assigned to the data. In the age example the setter might be something like:

void setAge(int age) {
if(age<3 || age>100) 
  return;
this.age=age;
}

assuming that students of age below 3 and over 100 aren’t allowed. So you are still hiding your data but allowing means to manipulate it in a way consistent with the logic of your module.