Getters method is return value in same class but return 0 in another class [JAVA]

First, I’m new in java and programming. I have a project that has OOP in it. Before I start writing this question, I already search for the answer in internet. There are some question like this, but I think that’s not a same question that I really mean.

So I make an encapsulation class that can setter & getter value in ClassA. Here’s the code:

class ClassA {
    private int a;

    public void setA(int a) {
        this.a = a;
    }

    public int getA() {
        return a;
    }

    public void print() {
        System.out.println("value a in ClassA: " + a);
    }
}

I’m trying to call that getter from ClassB and initialize it in "private int a". Here’s the code:

class ClassB {
    private ClassA classA = new ClassA();

    private int a = classA.getA();

    public void print() {
        System.out.println("value a in ClassB: " + a);
    }
}

And Here’s the driver code:

public class Main {
    public static void main(String[] args) {
        ClassA classA = new ClassA();
        ClassB classB = new ClassB();
    
        classA.setA(10);

        classA.print();
        classB.print();
    }
}

The output from driver code is:

value a in classA: 10
value a in classB: 0

The output that I want is:

value a in classA: 10
value a in classB: 10

In my expectation is when I setter setA with value 10 in ClassA, I can return that value from getA() into ClassB and initialize it to "int a" in that class. But when I try to print it, the value "int a" in ClassB is always set to 0 but "int a" in ClassA is initialized and print the correct value.

When I just call getA() in driver code like this:

System.out.println(classA.getA());

It’s still can print a correct value of 10, so that mean that method still can return a value.

The problem it just can’t get that return value into another class. Please help me to fix that return value from getter can be initialized in another class. Thank’s!

>Solution :

You instantiate class A two times, the instance from class B and Driver class is different, you didn’t assign value of a for instace in class B. you have to use one instance class of A

class ClassB {
private ClassA classA = new ClassA();

private int a = classA.getA();
public void setvalueOfA(int a){
   this.a=a;
   this.classA.setA(a);
  }

public void print() {
    System.out.println("value a in ClassB: " + a);
}

}

public class Main {
public static void main(String[] args) {
    ClassB classB = new ClassB();
    classB.setValueOfA(10);
    

    classB.classA.print();
    classB.print();
}

}