Groovy Total is an additional Instance method

class Student {
   int StudentID;
   String StudentName;
	
   int Marks1;
   int Marks2;
   int Marks3;
	
   int Total() {
      return Marks1+Marks2+Marks3;
   }
	
   static void main(String[] args) {

      Student st = new Student();
      st.StudentID = 1;
      st.StudentName="Joe";
		
      st.Marks1 = 10;
      st.Marks2 = 20;
      st.Marks3 = 30;
		
      println(st.Total());
   }
}