Chapter: Everything is an Object

Exercise 4: (1) Turn the DataOnly code fragments into a program that compiles and runs.

Again, not completely sure what they're after, but here is one that works:

public class Excercise4 {
    public static void main(String[] args) {
        DataOnly data = new DataOnly();
        
        data.i = 20;
        data.d = 1.23;
        data.b = false;
        
        System.out.println(data.i);
        System.out.println(data.d);
        System.out.println(data.b);
    }

}

class DataOnly {
    int i;
    double d;
    boolean b;
}

In Lisp:

(defclass data-only ()
  ((i :accessor the-int :initform 20)
   (d :accessor the-double :initform 1.23)
   (b :accessor the-bool :initform nil)))

(setf data (make-instance 'data-only))
(print (list (the-int data)
             (the-double data)
             (the-bool data)))

In Python:

class DataOnly:
    i = 20
    d = 1.23
    b = False

data = DataOnly()

print data.i
print data.d
print data.b