How can a class listen to other class's aoutput

Question

I have 2 classes which are both unrelated. but i want one class to listen to the output emitted by the other class. eg, class A continuosly prints messages and these messages, i want to be there in class B ...
Any suggestions?

Answer 1

I have 2 classes which are both unrelated. but i want
one class to listen to the output emitted by the
other class. eg, class A continuosly prints messages
and these messages, i want to be there in class B
Any suggestions?Classes do not listen to other classes but objects created from the classes can listen to other objects.
eg.
class A {
    public void sendMessage(B b) {
       b.setMessage(String aMessageFormA);
    public static void main(String[] args) {
        A a = new A();
        B b = new B();
        a.sendMessage(b);
        b.printMessageFromA();
}