Having to use a superclass call in display is somewhat restrictive in the ways in which...

Having to use a superclass call in display is somewhat restrictive in the ways in which we can format the output, because it is dependent on the way the superclass formats its fields. Make any necessary changes to the Post class and to the display method of MessagePost so that it produces the output shown in Figure 9.11. Any changes you make to the Post class should be visible only to its subclasses. Hint: You could add protected accessors to do this.

Figure 9.11 Output from display mixing subclass and superclass details (shaded areas represent superclass details)