为什么对象类方法将类的实例作为其参数

Question

To explain my question, in below code why do I have to pass object/instance of a class just to see how toString method is being overridden and why does the toString method, doesn't have parameter of type class to accept that object ?

Class Teacher

{

         public String toString()

         {

            return("Hello")
         }
}

Class TestTeacher

{

          public static void main(String []arr)
          {
               Teacher obj = new Teacher();
                System.out.println(obj);
          } 
}

Answer 1

why do I have to pass object/instance of a class just to see how toString method is being overridden

You do not need to pass the object to the toString method, you can just call

Teacher obj = new Teacher();
String output = obj.toString();
System.out.println(output);

and why does the toString method have an parameter of type class to accept that object ?

It has not. I think you are confused because you call the normal println function with the object. In turn internally the toString function is called to be able to print something to the standard output. So the object here is not the parameter of toString but is the parameter of the println function.