Help, I do not understand this lessson

Code runs ... fuzzy why this.age was the change ... Please clarify

public int age = 20;
        public void adjustAge(int age) {        // method parameter named age

tested with many . operators ,,,   // this specifies this Person class versus the one instantiated in main () ???
            this.age = age + 20;                     // increase age
            System.out.println("The age in adjustAge() is " + age);

just put the "this.age". this is the only thing i modified. it worked.

The weird part to me, is if you RUN it in IntelliJ IDEA, the result is always 15, and it also only prints 1 line, not 3........

I understand now, thank you everyone for your reply. :)

Hi! Han! Welcome to codegym.cc/help section. Well it is pretty easy. As Abhilash said. Abhilash is right w.r.t the Solution class. You need to study more about "this" keyword in java. "this" keyword is used for the object reference itself or you can say "this object". Go through classes and objects below, https://codegym.cc/groups/posts/33-getting-started-with-classes-writing-your-own-classes-constructors https://codegym.cc/groups/posts/34-methods You will find out the answer. In the following one, https://codegym.cc/quests/lectures/questsyntax.level04.lecture01 Cheers!

Whenever a Person class's object is created, the object's age is initially set to 20. We are then printing the person's age. (i.e. 20) After that, we are calling the instance method (adjustAge). Here the objective is to change the object's reference of age to 40. The twist in the method is that both the variable in the Person class and the argument in the method 'adjustAge' are both 'age'. When the program is run the class variable age is only modified and not the object's reference. To specifically modify the object's reference of age, we use 'this'. this.age = this.age + 20;