private « encapsulation « Java Class Q&A

1. How do you take decision to define a variable "private"?    stackoverflow.com

I have attended a job interview. The interviewer asked me why you need private variable. If you achieve something by defining a variable private, can't you achieve the same by defining ...

2. Wt's the mean by "Data Encapsulation" ? Use private data field/method ? if    stackoverflow.com

Say i have a class A and Class B extends Class A

Class A{
    private int x;

    private void m1{

    }

}
Class B extends ...