Why This ?

The static variable belongs to the class only. It is not part of any object. If the variable 'name' in the task were static, it would be referred to as Chat.name. Static variable is shared by all objects. There is only one "instance" of a static variable. Study this program and the output:

public class Chat {
    private static String name = "nameless cat"; // here the static 'name' variable is Chat.name, not this.name

    public void setName(String chatName) {

        this.name = chatName;
    }

    public static void main(String[] args) {
        Chat chat1 = new Chat();
        chat1.setName("Simba");

        Chat chat2 = new Chat();
        chat2.setName("Tiger");

        Chat chat3 = new Chat();
        chat3.setName("Lily");

        System.out.println(chat1.name);
        System.out.println(chat2.name);
        System.out.println(chat3.name);
        System.out.println(Chat.name);
    }
}

OUTPUT: Lily Lily Lily Lily All objects have access to this common variable, so you can also refer to it like this: this.name and also like this: Chat.name But in the task you are asking about, the name variable is NOT STATIC, it is an instance variable. Each object will have an OWN 'NAME', with different string value. Therefore, 'Chat.name' formula does not exist in that program. (The Chat.name would be a static 'name' variable, but there is not any static 'name' variable in that program.)