Java encapsulation [duplicate]

Answer 1

My question is if we can access the variables (data) though via getters and setters, how come data is hidden or safe?

You can encapsulate the logic under getters/setters. For example,

public void setAge(int age) {
    if (age < 0) {
        this.age = 0;
    }
    else {
        this.age = age;
    }
}