Interaction between two classes - class

Question

I want to know the best way to "share" or have access to attributes between 2 classes like this :
class A {
public A() {
B myClassB = new B();
}
int attributeA;
}
Class B {
int foo() {
// I want to have something like : return attributeA;
}
}
I hope that it's clear. If someone has a better way to ask the question let me know 'cause I really don't know how.
Thanks.

Answer 1

I would say by encapsulation you could share the fields (attributes) between classes. It is a fundamental OOP concept which helps a programmer to modify the already implemented code without breaking the code of others who use the fields.
Consider the below example (Java)
public class Person{
public String name = "John";
public int age = 25;
}
Sharing Person class's attributes with another class
public class EncapTest {
public static void main(String[] args) {
Person p = new Person();
p.name = "Tom";
p.age = 20;
System.out.println(p.name);
System.out.println(p.age);
}
}
The above approach is bad way to share(access) attributes between classes because any one can change the fields because they are public. So when you change them, they get changed for everyone (even for those who didn't want). It is like you're breaking the code of others.
See the below example which uses encapsulation
public class Person{
private String name;
private int age;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public int getName() {
return age;
}
}
Sharing Person class's attributes with another class
public class EncapTest {
public static void main(String[] args) {
Person p = new Person();
p.setName("Tom");
p.setAge(20)
System.out.println(p.getName());
System.out.println(p.getAge());
}
}
By making the attributes private and accessing them using the getters and setters methods, you are hiding the attributes with in the class. So whenever you set the attributes in another class, you're not breaking other programmers' code.